├── SimpleRadio.jpg ├── makefile ├── time-services.h ├── clock-control.h ├── time-signal.c ├── time-services.c ├── README.md ├── clock-control.c └── LICENSE /SimpleRadio.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/harlock974/time-signal/HEAD/SimpleRadio.jpg -------------------------------------------------------------------------------- /makefile: -------------------------------------------------------------------------------- 1 | PROGRAM=time-signal 2 | $(PROGRAM) : $(PROGRAM).c 3 | gcc -Wall -O2 -s -o $(PROGRAM) -no-pie *.c 4 | -------------------------------------------------------------------------------- /time-services.h: -------------------------------------------------------------------------------- 1 | /* 2 | time-services.h - part of timesignal, a JJY/MSF/WWVB/DCF77 3 | radio transmitter for Raspberry Pi 4 | Copyright (C) 2023 Pierre Brial 5 | 6 | Parts of this code is based on txtempus code written by Henner Zeller 7 | Source: https://github.com/hzeller/txtempus 8 | Copyright (C) 2018 Henner Zeller 9 | Licensed under the GNU General Public License, version 3 or later 10 | 11 | This program is free software: you can redistribute it and/or modify 12 | it under the terms of the GNU General Public License as published by 13 | the Free Software Foundation, either version 3 of the License, or 14 | (at your option) any later version. 15 | 16 | This program is distributed in the hope that it will be useful, 17 | but WITHOUT ANY WARRANTY; without even the implied warranty of 18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 | GNU General Public License for more details. 20 | 21 | You should have received a copy of the GNU General Public License 22 | along with this program. If not, see . 23 | */ 24 | 25 | #include 26 | #include 27 | #include 28 | #include 29 | #include 30 | 31 | enum time_service {JJY, DCF77, WWVB, MSF}; 32 | 33 | uint64_t prepareMinute(enum time_service service, time_t t); 34 | 35 | int getModulationForSecond(enum time_service service,uint64_t time_bits,int sec); 36 | -------------------------------------------------------------------------------- /clock-control.h: -------------------------------------------------------------------------------- 1 | /* 2 | time-services.h - part of timesignal, a JJY/MSF/WWVB/DCF77 3 | radio transmitter for Raspberry Pi 4 | Copyright (C) 2023 Pierre Brial 5 | 6 | Parts of this code is based on txtempus code written by Henner Zeller 7 | Source: https://github.com/hzeller/txtempus 8 | Copyright (C) 2018 Henner Zeller 9 | Licensed under the GNU General Public License, version 3 or later 10 | 11 | This program is free software: you can redistribute it and/or modify 12 | it under the terms of the GNU General Public License as published by 13 | the Free Software Foundation, either version 3 of the License, or 14 | (at your option) any later version. 15 | 16 | This program is distributed in the hope that it will be useful, 17 | but WITHOUT ANY WARRANTY; without even the implied warranty of 18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 | GNU General Public License for more details. 20 | 21 | You should have received a copy of the GNU General Public License 22 | along with this program. If not, see . 23 | */ 24 | 25 | #include 26 | #include 27 | #include 28 | #include 29 | #include 30 | #include 31 | #include 32 | #include 33 | #include 34 | #include 35 | 36 | bool GPIO_init(); 37 | double StartClock(double requested_freq); 38 | void StopClock(); 39 | void EnableClockOutput(bool on); // Enable clock output on GPIO4 40 | -------------------------------------------------------------------------------- /time-signal.c: -------------------------------------------------------------------------------- 1 | /* 2 | time-signal.c - a JJY/MSF/WWVB/DCF77 radio transmitter for Raspberry Pi 3 | Copyright (C) 2023 Pierre Brial 4 | 5 | Parts of this code is based on txtempus code written by Henner Zeller 6 | Source: https://github.com/hzeller/txtempus 7 | Copyright (C) 2018 Henner Zeller 8 | Licensed under the GNU General Public License, version 3 or later 9 | 10 | This program is free software: you can redistribute it and/or modify 11 | it under the terms of the GNU General Public License as published by 12 | the Free Software Foundation, either version 3 of the License, or 13 | (at your option) any later version. 14 | 15 | This program is distributed in the hope that it will be useful, 16 | but WITHOUT ANY WARRANTY; without even the implied warranty of 17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18 | GNU General Public License for more details. 19 | 20 | You should have received a copy of the GNU General Public License 21 | along with this program. If not, see . 22 | */ 23 | 24 | #include 25 | #include 26 | #include 27 | #include 28 | #include 29 | #include "time-services.h" 30 | #include "clock-control.h" 31 | 32 | int usage(const char *msg, const char *progname) 33 | { 34 | fprintf(stderr, "%susage: %s [options]\n" 35 | "Options:\n" 36 | "\t-s : Service; one of " 37 | "'DCF77', 'WWVB', 'JJY40', 'JJY60', 'MSF'\n" 38 | "\t-v : Verbose.\n" 39 | "\t-c : Carrier wave only.\n" 40 | "\t-h : This help.\n", 41 | msg, progname); 42 | return 1; 43 | } 44 | 45 | void signaux(int sigtype) 46 | { 47 | switch(sigtype) 48 | { 49 | case SIGINT : printf ("\nSIGINT");break; 50 | case SIGTERM : printf ("\nSIGTERM");break; 51 | default : printf ("\nUnknow %d",sigtype); 52 | } 53 | StopClock(); 54 | printf (" signal received - Programme terminé\n"); 55 | exit(0); 56 | } 57 | 58 | int main(int argc, char *argv[]) 59 | { 60 | bool 61 | verbose = false, 62 | carrier_only = false; 63 | 64 | int 65 | modulation, 66 | frequency=60000, 67 | opt; 68 | 69 | uint64_t minute_bits; 70 | char 71 | *time_source="", 72 | date_string[] = "1969-07-21 00:00:00"; //,*lineptr; 73 | //size_t n=0; 74 | enum time_service service; 75 | time_t now,minute_start; 76 | struct timespec target_wait; 77 | struct tm tv; 78 | //FILE *f; 79 | 80 | signal(SIGINT,signaux); 81 | signal(SIGTERM,signaux); 82 | 83 | puts("time-signal, a JJY/MSF/WWVB/DCF77 radio transmitter"); 84 | puts("Copyright (C) 2023 Pierre Brial"); 85 | puts("This program comes with ABSOLUTELY NO WARRANTY."); 86 | puts("This is free software, and you are welcome to"); 87 | puts("redistribute it under certain conditions.\n"); 88 | 89 | while ((opt = getopt(argc, argv, "vs:hc")) != -1) 90 | { 91 | switch (opt) 92 | { 93 | case 'v': 94 | verbose = true; 95 | break; 96 | case 's': 97 | time_source = optarg; 98 | break; 99 | case 'c': 100 | carrier_only = true; 101 | break; 102 | default: 103 | return usage("", argv[0]); 104 | } 105 | } 106 | 107 | if (strcasecmp(time_source, "DCF77") == 0) 108 | { 109 | frequency = 77500; 110 | service = DCF77; 111 | } 112 | else if (strcasecmp(time_source, "WWVB") == 0) service = WWVB; 113 | else if (strcasecmp(time_source, "JJY40") == 0) 114 | { 115 | frequency = 40000; 116 | service = JJY; 117 | } 118 | else if (strcasecmp(time_source, "JJY60") == 0) service = JJY; 119 | else if (strcasecmp(time_source, "MSF") == 0) service = MSF; 120 | else return usage("Please choose a service name with -s option\n", argv[0]); 121 | 122 | GPIO_init (); 123 | StartClock(frequency); 124 | 125 | if (carrier_only) EnableClockOutput(1); 126 | 127 | // Give max priority to this programm 128 | struct sched_param sp; 129 | sp.sched_priority = 99; 130 | sched_setscheduler(0, SCHED_FIFO, &sp); 131 | 132 | now = time(NULL); 133 | minute_start = now - now % 60; // round to minute 134 | 135 | while(1) 136 | { 137 | if (carrier_only) continue; 138 | localtime_r(&minute_start, &tv); 139 | strftime(date_string, sizeof(date_string), "%Y-%m-%d %H:%M:%S", &tv); 140 | printf("%s\n",date_string); 141 | minute_bits = prepareMinute(service,minute_start); 142 | 143 | for (int second = 0; second < 60; ++second) 144 | { 145 | modulation = getModulationForSecond(service,minute_bits,second); 146 | 147 | // First, let's wait until we reach the beginning of that second 148 | target_wait.tv_sec = minute_start + second; 149 | target_wait.tv_nsec = 0; 150 | clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &target_wait, NULL); 151 | 152 | if (service == JJY) EnableClockOutput(1); // Set signal to HIGH 153 | else EnableClockOutput(0); // Set signal to LOW 154 | 155 | if (verbose) 156 | { 157 | fprintf(stderr,"%03d ",modulation); 158 | if ((second+1)%15 == 0) fprintf(stderr,"\n"); 159 | } 160 | 161 | target_wait.tv_nsec = modulation*1e6; 162 | clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &target_wait, NULL); 163 | 164 | if (service == JJY) EnableClockOutput(0); //signal to LOW 165 | else EnableClockOutput(1); // Set signal to HIGH 166 | } 167 | 168 | minute_start += 60; 169 | } 170 | } 171 | -------------------------------------------------------------------------------- /time-services.c: -------------------------------------------------------------------------------- 1 | /* 2 | time-services.c - part of timesignal, a JJY/MSF/WWVB/DCF77 3 | radio transmitter for Raspberry Pi 4 | Copyright (C) 2023 Pierre Brial 5 | 6 | Parts of this code is based on txtempus code written by Henner Zeller 7 | Source: https://github.com/hzeller/txtempus 8 | Copyright (C) 2018 Henner Zeller 9 | Licensed under the GNU General Public License, version 3 or later 10 | 11 | This program is free software: you can redistribute it and/or modify 12 | it under the terms of the GNU General Public License as published by 13 | the Free Software Foundation, either version 3 of the License, or 14 | (at your option) any later version. 15 | 16 | This program is distributed in the hope that it will be useful, 17 | but WITHOUT ANY WARRANTY; without even the implied warranty of 18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 | GNU General Public License for more details. 20 | 21 | You should have received a copy of the GNU General Public License 22 | along with this program. If not, see . 23 | */ 24 | 25 | 26 | #include "time-services.h" 27 | 28 | // Similar to WWVB, JJY uses BCD, but usually has a zero bit between the digits. 29 | // So let's call it 'padded' BCD. 30 | static uint64_t to_padded5_bcd(int n) 31 | { 32 | return (((n / 100) % 10) << 10) | (((n / 10) % 10) << 5) | (n % 10); 33 | } 34 | 35 | // Regular BCD for the year encoding. 36 | static uint64_t to_bcd(int n) 37 | { 38 | return (((n / 100) % 10) << 8) | (((n / 10) % 10) << 4) | (n % 10); 39 | } 40 | 41 | static uint64_t parity(uint64_t d, uint8_t from, uint8_t to_including) 42 | { 43 | uint8_t result = 0; 44 | for (int bit = from; bit <= to_including; ++bit) 45 | { 46 | if (d & (1LL << bit)) result++; 47 | } 48 | return result & 0x1; 49 | } 50 | 51 | static uint64_t is_leap_year(int year) 52 | { 53 | return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0); 54 | } 55 | 56 | uint64_t prepareMinute(enum time_service service, time_t t) 57 | { 58 | struct tm breakdown, tomorrow; 59 | time_t tomorrow_t; 60 | uint64_t time_bits = 0, // All the unused bits are zero. 61 | a_bits = 0, // MSF 62 | b_bits = 0; // MSF 63 | 64 | switch(service) 65 | { 66 | case JJY: 67 | // The JJY format uses Bit-Bigendianess, so we'll start with the first 68 | // bit left in our integer in bit 59. 69 | localtime_r(&t, &breakdown); // If in JP, this is Japan Standard Time 70 | time_bits |= to_padded5_bcd(breakdown.tm_min) << (59 - 8); 71 | time_bits |= to_padded5_bcd(breakdown.tm_hour) << (59 - 18); 72 | time_bits |= to_padded5_bcd(breakdown.tm_yday + 1) << (59 - 33); 73 | time_bits |= to_bcd(breakdown.tm_year % 100) << (59 - 48); 74 | time_bits |= to_bcd(breakdown.tm_wday) << (59 - 52); 75 | 76 | time_bits |= parity(time_bits, 59-18, 59-12) << (59 - 36); // PA1 77 | time_bits |= parity(time_bits, 59-8, 59-1) << (59 - 37); // PA2 78 | 79 | // There is a different 'service announcement' encoding in minute 15 and 45, 80 | // but let's just ignore that for now. Consumer clocks probably don't care. 81 | break; 82 | 83 | case DCF77: 84 | t += 60; // We're sending the _upcoming_ minute. 85 | localtime_r(&t, &breakdown); 86 | // Little endian bits. So we store big-endian bits and start transmitting from bit 0 87 | time_bits |= (breakdown.tm_isdst ? 1 : 0) << 17; 88 | time_bits |= (breakdown.tm_isdst ? 0 : 1) << 18; 89 | time_bits |= (1<<20); // start time bit. 90 | time_bits |= to_bcd(breakdown.tm_min) << 21; 91 | time_bits |= to_bcd(breakdown.tm_hour) << 29; 92 | time_bits |= to_bcd(breakdown.tm_mday) << 36; 93 | time_bits |= to_bcd(breakdown.tm_wday ? breakdown.tm_wday : 7) << 42; 94 | time_bits |= to_bcd(breakdown.tm_mon + 1) << 45; 95 | time_bits |= to_bcd(breakdown.tm_year % 100) << 50; 96 | 97 | time_bits |= parity(time_bits, 21, 27) << 28; 98 | time_bits |= parity(time_bits, 29, 34) << 35; 99 | time_bits |= parity(time_bits, 36, 57) << 58; 100 | break; 101 | 102 | case WWVB: 103 | gmtime_r(&t, &breakdown); // Time transmission is always in UTC. 104 | // The WWVB format uses Bit-Bigendianess, so we'll start with the first 105 | // bit left in our integer in bit 59. 106 | time_bits |= to_padded5_bcd(breakdown.tm_min) << (59 - 8); 107 | time_bits |= to_padded5_bcd(breakdown.tm_hour) << (59 - 18); 108 | time_bits |= to_padded5_bcd(breakdown.tm_yday + 1) << (59 - 33); 109 | time_bits |= to_padded5_bcd(breakdown.tm_year % 100) << (59 - 53); 110 | time_bits |= is_leap_year(breakdown.tm_year + 1900) << (59 - 55); 111 | 112 | // Need local time for now and tomorrow to determine DST status. 113 | localtime_r(&t, &breakdown); 114 | tomorrow_t = t + 86400; 115 | localtime_r(&tomorrow_t, &tomorrow); 116 | time_bits |= (tomorrow.tm_isdst ? 1 : 0) << (59 - 57); 117 | time_bits |= (breakdown.tm_isdst ? 1 : 0) << (59 - 58); 118 | break; 119 | 120 | case MSF: 121 | t += 60; // We're sending the _upcoming_ minute. 122 | localtime_r(&t, &breakdown); // Local time, e.g. British standard time. 123 | 124 | // The MSF format uses Bit-Bigendianess, so we'll start with the first 125 | // bit left in our integer in bit 59. 126 | 127 | a_bits |= to_bcd(breakdown.tm_year % 100) << (59 - 24); 128 | a_bits |= to_bcd(breakdown.tm_mon + 1) << (59 - 29); 129 | a_bits |= to_bcd(breakdown.tm_mday) << (59 - 35); 130 | a_bits |= to_bcd(breakdown.tm_wday) << (59 - 38); 131 | a_bits |= to_bcd(breakdown.tm_hour) << (59 - 44); 132 | a_bits |= to_bcd(breakdown.tm_min) << (59 - 51); 133 | 134 | // First couple of bits: DUT; not being set. 135 | // (59 - 53): summer time warning. Not set. 136 | b_bits |= (parity(a_bits, 59-24, 59-17)==0) << (59 - 54); // Year parity 137 | b_bits |= (parity(a_bits, 59-35, 59-25)==0) << (59 - 55); // Day parity 138 | b_bits |= (parity(a_bits, 59-38, 59-36)==0) << (59 - 56); // Weekday parity 139 | b_bits |= (parity(a_bits, 59-51, 59-39)==0) << (59 - 57); // Time parity 140 | b_bits |= breakdown.tm_isdst << (59 - 58); 141 | time_bits = a_bits | b_bits; 142 | break; 143 | 144 | default: 145 | fprintf(stderr,"Time service still not implemented.\n"); 146 | exit(1); 147 | } 148 | 149 | return time_bits; 150 | } 151 | 152 | int getModulationForSecond(enum time_service service,uint64_t time_bits,int sec) 153 | { 154 | bool bit; 155 | switch(service) 156 | { 157 | case JJY: 158 | if (sec == 0 || sec % 10 == 9 || sec > 59) return 200; 159 | bit = time_bits & (1LL << (59 - sec)); 160 | return (bit ? 500 : 800); 161 | 162 | case DCF77: 163 | if (sec >= 59) return 0; 164 | bit = time_bits & (1LL << sec); 165 | return (bit ? 200 : 100); 166 | 167 | case WWVB: 168 | if (sec == 0 || sec % 10 == 9 || sec > 59) return 800; 169 | bit = time_bits & (1LL << (59 - sec)); 170 | return (bit ? 500 : 200); 171 | 172 | case MSF: 173 | if (sec == 0) return 500; 174 | bit = time_bits & (1LL << (59 - sec)); 175 | return 100+bit*100+((sec>52)&&(sec<59))*100; 176 | 177 | default: 178 | fprintf(stderr,"Time service still not implemented.\n"); 179 | exit(1); 180 | } 181 | } 182 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # time-signal 2 | A multiband time signal radio transmitter for Raspberry Pi. 3 | 4 | **time-signal** allows to convert a Raspberry Pi to a radio time server using using either JJY, MSF, WWVB or DCF77 protocol, allowing to automatically adjust time on radio-controlled watch or clock. 5 | 6 | ## Platforms 7 | 8 | **time-signal** has been succesfully tested on : 9 | * Raspberry Pi Zero W 10 | * Raspberry Pi 3 Model B Rev 1.2 11 | * Raspberry Pi 4 Model B Rev 1.1 12 | 13 | ## Build 14 | 15 | Inside the directory where the source files are, simply type `make` 16 | 17 | ## Usage 18 | 19 | ``` 20 | sudo ./time-signal [OPTIONS] 21 | ``` 22 | ### Options 23 | 24 | -s : Time service: either of DCF77, WWVB, JJY40, JJY60, MSF 25 | 26 | -v : Verbose. Show modulation enveloppe. 27 | 28 | -c : Send carrier wave only, without time signal. Usefull for testing frequencies. 29 | 30 | -h : This help. 31 | 32 | ## Hardware 33 | 34 | ### Circuits 35 | 36 | **time-signal** uses GPIO 4 (pin 7) to transmit the modulated carrier wave and a Ground pin. 5V power pin could also be used by your circuit if you want to amplify the signal. 37 | 38 | ![Capture d’écran_2023-09-25_21-27-04](https://github.com/harlock974/time-signal/assets/6268242/d27c548d-a9a9-4dd3-8360-b7247b49799a) 39 | _[Raspberry Pi pinout](https://pinout.xyz)_ 40 | 41 | The simplest hardware you can use to transmit the signal is to connect a coil and a 220Ω resistor in serie between GPIO4 and a ground pin : 42 | 43 | ![IMG_20230925_212405](https://github.com/harlock974/time-signal/assets/6268242/79d53d74-a45c-4ef1-8484-cf3a85fff586) 44 | 45 | Here with a 60cm wire and 14 turns of 13mm diameter, the range is quite decent : 10cm for DCF77 and 45cm for JJY at 40 kHz. 46 | 47 | For a longer range and still simple circuit, you can use a ferrite antenna salvaged from an AM receiver with a N mosfet as amplifier. You'll then have this 3 components + antenna circuit : 48 | 49 | ![MOSFET_OSCILLATOR_JJY40 EMF](https://github.com/harlock974/time-signal/assets/6268242/0602c816-f4b7-4955-aaed-0eb1e36e3022) 50 | 51 | ![DSC_4398s](https://github.com/harlock974/time-signal/assets/6268242/3a3ce337-c3cd-41d2-af07-a76bfd2c779e) 52 | 53 | _The hairy 3 components circuit_ 54 | 55 | If you don't have a mosfet, you can use a NPN transistor instead with a 4.7K resistor between its base and GPIO4. 56 | 57 | ![](SimpleRadio.jpg) 58 | 59 | C1 capacitor value depends on antenna inductance and target frequency (see below). 60 | 61 | As small mosfets like BS270 can handle up to 250 mA, you can design a more powerful transmitter with two complementary mosfets as a NOT gate and a lower value resistor : 62 | 63 | ![DUAL-MOSFET_OSCILLATOR_JJY40s](https://github.com/harlock974/time-signal/assets/6268242/b53c2782-183a-449b-9a01-d93ef6c92044) 64 | 65 | 66 | I successfully tested these circuits with JJY40 et DCF77 signals and reached a range of ten meters with JJY40 and the dual mosfet configuration. 67 | 68 | ![269642939-9069a2a0-c241-44fa-8030-728f90dce124](https://github.com/harlock974/time-signal/assets/6268242/c74016e5-7b95-4ce8-92b7-7234ac943319) 69 | 70 | _G-Shock strong reception (L3)_ 71 | 72 | # Antennas 73 | 74 | There is much concern in radio communities about strength of the signal related to legal limits. But with low frequencies, it is very difficult to design a long range transmitting antenna : 75 | 76 | "The problem of designing compact, efficient, and broadband antennas capable of transmitting signals in the very low frequency (VLF, 3-30 kHz) and low frequency (LF, 30-300 kHz) bands has plagued engineers for decades [...] For instance, attempting to build a standard quarter-wave monopole at 30 kHz would require an antenna to be 2.5 km long, which is roughly three times longer than the tallest building on Earth"(1) 77 | 78 | For example, the [Ohtakadoyayama station](https://jjy.nict.go.jp/jjy/trans/index-e.html) antenna transmitting JJY 40 kHz signal is an umbrella type 250m high, and the [Mainflingen station](https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77/dcf77-transmitting-facilities.html) transmitting DCF77 at 77.5 kHz is a T-type 150m high. 79 | 80 | So building an efficient transmitting antenna is far beyond practical limits for the hobbyist. The solution here is to use a compact ferrite rod antenna. These ones can be salvaged from an AM Radio, as there is no longer AM broadcasting, or from a cheap DCF77 module. But "ferrite rod antennas are normally only used for receiving. They are rarely used for transmitting anything above low levels of power in view of their poor efficiency. They can be used as a very compact form of transmitting antenna for applications where efficiency is not an issue and where power levels are very low. If power levels rise too high then heat dissipation in the ferrite becomes an issue"(2). 81 | 82 | Hence don't expect to transmit outside your house. The longest range I succeeded to reach is 10 meters with a 40 kHz signal, with direct line of sight. The antenna was powered by the 5 V dual mosfet amplifier circuit. Increasing the voltage didn't improve the range. 83 | 84 | You'll have to adjust the resonance of your antenna for the requested frequency, with the capacitor. Capacitor value depends on antenna inductance L and target frequency f : 85 | 86 | C = 1 / (4×π²×L×f²)` 87 | 88 | AM antennas have usually an inductance between 500 and 700 µH, so the theoretical C values are : 89 | 90 | * 40000 Hz : 26 nF 91 | * 60000 Hz : 12 nF 92 | * 77500 Hz : 7 nF 93 | 94 | If you have an oscilloscope, connect it between the antenna and the capacitor, run time-signal with '-c' option and change the value of the capacitor to obtain the larger and cleaner signal, that is a nice sinusoid. 95 | 96 | | Poorly tuned antenna (40kHz, 10nF) | Quite well tuned antenna (40kHz, 33nF) | 97 | | --- | --- | 98 | | ![DSC_4430-40kHz-10nF-Oregon-s](https://github.com/harlock974/time-signal/assets/6268242/f2e38580-56a7-433d-a44b-d1c1c54e14e7) | ![DSC_4429-40kHz-33nF-Oregon-s](https://github.com/harlock974/time-signal/assets/6268242/ba1f4ecf-09a3-4918-a5db-98147c262389) | 99 | 100 | # Credits and references 101 | 102 | Large parts of time-signal code come from Henner Zeller [txtempus](https://github.com/hzeller/txtempus). The main differences between time-signal and txtempus are : 103 | 104 | * txtempus works on Raspberry Pi 3 and Zero W and Jetson Nano ; time-signal works on Raspberry Pi 3, 4 and Zero W. 105 | * txtempus is written in C++ while time-signal is written in C and doesn't need CMake to be built. 106 | * time-signal doesn't use an attenuation pin, so the required hardware is simpler. 107 | 108 | Some useful references : 109 | 110 | 1. New ideas about designing low frequencies antennas : Slevin, Cohen and Golkowski (2021), "Wideband VLF/LF Transmission from an Electrically-Small Antenna by Means of Time-Varying Non-Reciprocity via High-Speed Switches", URSI GASS 2021, Rome, Italy, 28 August - 4 September 2021. 111 | 2. Ferrite antennas : https://www.electronics-notes.com/articles/antennas-propagation/ferrite-rod-bar-antenna/basics-tutorial.php 112 | 3. Discussion in txtempus github about how to design longest range transmitters : https://github.com/hzeller/txtempus/issues/8 113 | 4. Andreas Spiess video about designing a DCF77 transmitter : https://youtu.be/6SHGAEhnsYk 114 | 5. Wikipedia pages about time services : [DCF77](https://en.wikipedia.org/wiki/DCF77), [WWVB](https://en.wikipedia.org/wiki/WWVB), [MSF](https://en.wikipedia.org/wiki/Time_from_NPL_(MSF)), [JJY](https://en.wikipedia.org/wiki/JJY). 115 | -------------------------------------------------------------------------------- /clock-control.c: -------------------------------------------------------------------------------- 1 | #include "clock-control.h" 2 | 3 | // -- Implementation for Raspberry Pi Series -- 4 | 5 | // Raspberry 1 and 2 have different base addresses for the periphery 6 | #define BCM2708_PERI_BASE 0x20000000 7 | #define BCM2709_PERI_BASE 0x3F000000 8 | #define BCM2711_PERI_BASE 0xFE000000 9 | 10 | #define GPIO_REGISTER_OFFSET 0x00200000 11 | #define CLOCK_REGISTER_OFFSET 0x00101000 12 | 13 | #define REGISTER_BLOCK_SIZE (4*1024) 14 | 15 | // GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x). 16 | #define INP_GPIO(g) *(gpio_port+((g)/10)) &= ~(7<<(((g)%10)*3)) 17 | #define OUT_GPIO(g) *(gpio_port+((g)/10)) |= (1<<(((g)%10)*3)) 18 | #define ALT0_GPIO(g) *(gpio_port+((g)/10)) |= (4<<(((g)%10)*3)) 19 | 20 | #define GPIO_SET *(gpio+7) // sets bits which are 1 ignores bits which are 0 21 | #define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0 22 | 23 | // Clock control 24 | #define CLK_PASSWD (0x5A << 24) 25 | #define CLK_CTL_MASH(x) ((x)<<9) 26 | #define CLK_CTL_BUSY (1<<7) 27 | #define CLK_CTL_KILL (1<<5) 28 | #define CLK_CTL_ENAB (1<<4) 29 | #define CLK_CTL_SRC(x) ((x)<<0) 30 | 31 | #define CLK_DIV_DIVI(x) ((x)<<12) 32 | #define CLK_DIV_DIVF(x) ((x)<< 0) 33 | 34 | #define CLK_CMGP0_CTL 28 35 | #define CLK_CMGP0_DIV 29 36 | 37 | volatile uint32_t *gpio_port; 38 | volatile uint32_t *gpio_set_bits; 39 | volatile uint32_t *gpio_clr_bits; 40 | volatile uint32_t *clk; 41 | 42 | enum RaspberryPiModel 43 | { 44 | PI_MODEL_1, 45 | PI_MODEL_2, 46 | PI_MODEL_3, 47 | PI_MODEL_4 48 | }; 49 | 50 | enum RaspberryPiModel piModel; 51 | 52 | void EnableClockOutput(bool on) 53 | { 54 | if (on) ALT0_GPIO(4); // Pinmux GPIO4 into outputting clock. 55 | else INP_GPIO(4); 56 | } 57 | 58 | void StopClock() 59 | { 60 | *(clk + CLK_CMGP0_CTL) = CLK_PASSWD | CLK_CTL_KILL; 61 | // Wait until clock confirms not to be busy anymore. 62 | while (clk[CLK_CMGP0_CTL] & CLK_CTL_BUSY) usleep(10); 63 | EnableClockOutput(false); 64 | } 65 | 66 | // BCM2835-ARM-Peripherals.pdf, page 105 onwards. 67 | double StartClock(double requested_freq) 68 | { 69 | // Figure out best clock source to get closest to the requested 70 | // frequency with MASH=1. We check starting from the highest frequency to 71 | // find lowest jitter opportunity first. 72 | 73 | struct { int src; double frequency; } kClockSources[] = 74 | { 75 | { 7, piModel==PI_MODEL_4 ? 0 : 216.0e6 }, // HDMI <- this can be problematic if monitor connected 76 | { 1, piModel==PI_MODEL_4 ? 54.0e6 : 19.2e6 }, // regular oscillator 77 | }; 78 | 79 | int divI = -1; 80 | int divF = -1; 81 | int best_clock_source = -1; 82 | double smallest_error_so_far = 1e9; 83 | printf("Clock sources:\n"); 84 | for (size_t i = 0; i < sizeof(kClockSources)/sizeof(kClockSources[0]); ++i) 85 | { 86 | printf("%d : ",kClockSources[i].src); 87 | double division = kClockSources[i].frequency / requested_freq; 88 | if (division < 2 || division > 4095) 89 | { 90 | puts(""); 91 | continue; 92 | } 93 | int test_divi = (int) division; 94 | int test_divf = (division - test_divi) * 1024; 95 | double freq = kClockSources[i].frequency / (test_divi + test_divf/1024.0); 96 | double error = fabsl(requested_freq - freq); 97 | //printf("Clock source : %d freq : %.4f error : %.4f\n",kClockSources[i].src,freq,error); 98 | printf("freq : %.4f error : %.4f\n",freq,error); 99 | if (error >= smallest_error_so_far) continue; 100 | smallest_error_so_far = error; 101 | best_clock_source = i; 102 | divI = test_divi; 103 | divF = test_divf; 104 | } 105 | 106 | if (divI < 0) return -1.0; // Couldn't find any suitable clock. 107 | 108 | StopClock(); 109 | 110 | const uint32_t ctl = CLK_CMGP0_CTL; 111 | const uint32_t div = CLK_CMGP0_DIV; 112 | const uint32_t src = kClockSources[best_clock_source].src; 113 | const uint32_t mash = 1; // Good approximation, low jitter. 114 | 115 | clk[div] = CLK_PASSWD | CLK_DIV_DIVI(divI) | CLK_DIV_DIVF(divF); 116 | usleep(10); 117 | clk[ctl] = CLK_PASSWD | CLK_CTL_MASH(mash) | CLK_CTL_SRC(src); 118 | usleep(10); 119 | 120 | clk[ctl] |= CLK_PASSWD | CLK_CTL_ENAB; 121 | 122 | //EnableClockOutput(true); 123 | 124 | // There have been reports of different clock source frequencies. This 125 | // helps figuring out which source was picked. 126 | fprintf(stderr, "\nChoose clock %d at %gHz / %.3f = %.3f\n\n", 127 | kClockSources[best_clock_source].src, 128 | kClockSources[best_clock_source].frequency, 129 | divI + divF/1024.0, 130 | kClockSources[best_clock_source].frequency / (divI + divF/1024.0)); 131 | return kClockSources[best_clock_source].frequency / (divI + divF/1024.0); 132 | } 133 | 134 | enum RaspberryPiModel GetPiModel() 135 | { 136 | FILE *f; 137 | unsigned int pi_revision; 138 | char *lineptr; 139 | size_t n=0; 140 | f=fopen("/proc/cpuinfo","r"); 141 | if (f != NULL) 142 | { 143 | while (getline (&lineptr, &n, f) != -1) 144 | { 145 | if (strstr(lineptr, "Revision")) 146 | { 147 | sscanf(lineptr, "Revision : %x", &pi_revision); 148 | unsigned int pi_type = (pi_revision >> 4) & 0xff; 149 | printf("Pi type : 0x%02x\n",pi_type); 150 | switch (pi_type) 151 | { 152 | case 0x00: /* A */ 153 | case 0x01: /* B, Compute Module 1 */ 154 | case 0x02: /* A+ */ 155 | case 0x03: /* B+ */ 156 | case 0x05: /* Alpha ?*/ 157 | case 0x06: /* Compute Module1 */ 158 | case 0x09: /* Zero */ 159 | case 0x0c: /* Zero W */ 160 | return PI_MODEL_1; 161 | 162 | case 0x04: /* Pi 2 */ 163 | case 0x12: /* Zero W 2 (behaves close to Pi 2) */ 164 | return PI_MODEL_2; 165 | 166 | case 0x11: /* Pi 4 */ 167 | // A first test did not seem to work. Maybe the registers changed ? 168 | fprintf(stderr, "Note: Frequency generation is known to not work on Pi4; " 169 | "Use older Pis for now.\n"); 170 | return PI_MODEL_4; 171 | } 172 | } 173 | } 174 | } 175 | return PI_MODEL_3; 176 | } 177 | 178 | static uint32_t *mmap_bcm_register(off_t register_offset) 179 | { 180 | off_t base = BCM2709_PERI_BASE; // safe fallback guess. 181 | switch (piModel) 182 | { 183 | case PI_MODEL_1: base = BCM2708_PERI_BASE; break; 184 | case PI_MODEL_2: base = BCM2709_PERI_BASE; break; 185 | case PI_MODEL_3: base = BCM2709_PERI_BASE; break; 186 | case PI_MODEL_4: base = BCM2711_PERI_BASE; break; 187 | } 188 | 189 | int mem_fd; 190 | if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) 191 | { 192 | perror("can't open /dev/mem: "); 193 | return NULL; 194 | } 195 | 196 | uint32_t *result = (uint32_t*) mmap 197 | ( 198 | NULL, // Any adddress in our space will do 199 | REGISTER_BLOCK_SIZE, // Map length 200 | PROT_READ|PROT_WRITE, // Enable r/w on GPIO registers. 201 | MAP_SHARED, 202 | mem_fd, // File to map 203 | base + register_offset // Offset to bcm register 204 | ); 205 | 206 | close(mem_fd); 207 | 208 | if (result == MAP_FAILED) 209 | { 210 | perror("mmap error: "); 211 | fprintf(stderr, "MMapping from base 0x%lx, offset 0x%lx\n", base, register_offset); 212 | return NULL; 213 | } 214 | return result; 215 | } 216 | 217 | bool GPIO_init() 218 | { 219 | piModel = GetPiModel(); 220 | gpio_port = mmap_bcm_register(GPIO_REGISTER_OFFSET); 221 | if (gpio_port == NULL) 222 | { 223 | fprintf(stderr, "Need to be root\n"); 224 | return false; 225 | } 226 | gpio_set_bits = gpio_port + (0x1C / sizeof(uint32_t)); 227 | gpio_clr_bits = gpio_port + (0x28 / sizeof(uint32_t)); 228 | clk = mmap_bcm_register(CLOCK_REGISTER_OFFSET); 229 | return gpio_port != MAP_FAILED && clk != MAP_FAILED; 230 | } 231 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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No Surrender of Others' Freedom. 541 | 542 | If conditions are imposed on you (whether by court order, agreement or 543 | otherwise) that contradict the conditions of this License, they do not 544 | excuse you from the conditions of this License. If you cannot convey a 545 | covered work so as to satisfy simultaneously your obligations under this 546 | License and any other pertinent obligations, then as a consequence you may 547 | not convey it at all. For example, if you agree to terms that obligate you 548 | to collect a royalty for further conveying from those to whom you convey 549 | the Program, the only way you could satisfy both those terms and this 550 | License would be to refrain entirely from conveying the Program. 551 | 552 | 13. Use with the GNU Affero General Public License. 553 | 554 | Notwithstanding any other provision of this License, you have 555 | permission to link or combine any covered work with a work licensed 556 | under version 3 of the GNU Affero General Public License into a single 557 | combined work, and to convey the resulting work. The terms of this 558 | License will continue to apply to the part which is the covered work, 559 | but the special requirements of the GNU Affero General Public License, 560 | section 13, concerning interaction through a network will apply to the 561 | combination as such. 562 | 563 | 14. Revised Versions of this License. 564 | 565 | The Free Software Foundation may publish revised and/or new versions of 566 | the GNU General Public License from time to time. Such new versions will 567 | be similar in spirit to the present version, but may differ in detail to 568 | address new problems or concerns. 569 | 570 | Each version is given a distinguishing version number. If the 571 | Program specifies that a certain numbered version of the GNU General 572 | Public License "or any later version" applies to it, you have the 573 | option of following the terms and conditions either of that numbered 574 | version or of any later version published by the Free Software 575 | Foundation. If the Program does not specify a version number of the 576 | GNU General Public License, you may choose any version ever published 577 | by the Free Software Foundation. 578 | 579 | If the Program specifies that a proxy can decide which future 580 | versions of the GNU General Public License can be used, that proxy's 581 | public statement of acceptance of a version permanently authorizes you 582 | to choose that version for the Program. 583 | 584 | Later license versions may give you additional or different 585 | permissions. However, no additional obligations are imposed on any 586 | author or copyright holder as a result of your choosing to follow a 587 | later version. 588 | 589 | 15. Disclaimer of Warranty. 590 | 591 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 592 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 593 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY 594 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 595 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 596 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 597 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 598 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 599 | 600 | 16. Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | --------------------------------------------------------------------------------