├── .gitmodules ├── License.txt ├── Makefile ├── README.md └── main.c /.gitmodules: -------------------------------------------------------------------------------- 1 | [submodule "i2c"] 2 | path = i2c 3 | url = https://github.com/usedbytes/usi_i2c_slave.git 4 | [submodule "ws2812"] 5 | path = ws2812 6 | url = https://github.com/usedbytes/light_ws2812.git 7 | -------------------------------------------------------------------------------- /License.txt: -------------------------------------------------------------------------------- 1 | 2 | 3 | GNU GENERAL PUBLIC LICENSE 4 | Version 2, June 1991 5 | 6 | Copyright (C) 1989, 1991 Free Software Foundation, Inc. 7 | 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 8 | Everyone is permitted to copy and distribute verbatim copies 9 | of this license document, but changing it is not allowed. 10 | 11 | Preamble 12 | 13 | The licenses for most software are designed to take away your 14 | freedom to share and change it. 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If this is what you want to do, use the GNU Library General 342 | Public License instead of this License. -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/usedbytes/neopixel_i2c/c210f5080bb23d22ff343518190004b7032229a8/Makefile -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # neopixel_i2c_slave (picopixel) 2 | 3 | This is an AVR-based neopixel driver. It accepts commands over i2c to drive a 4 | a number of ws2812 LED pixels. 5 | 6 | The code on the master branch is set up for an Attiny85, with the LEDs on PB3, 7 | using an usbasp programmer. The fuses should be set to use 8 MHz internal 8 | oscillator, **no divider** 9 | 10 | ## How many LEDs? 11 | The number of LEDs is currently hardcoded in the firmware. The maximum number 12 | depends on the amount of RAM available on your AVR. 13 | An Attiny45 should be able to drive 82 LEDs, and an Attiny85, 167. 14 | 15 | ## Circuit 16 | 17 | Suggested circuit. 18 | 19 | ``` 20 | ^ VCC 21 | | 22 | +--------+--------------+-------------+-----+-------+ 23 | | | | | | 24 | | |"| 10k | | | 25 | | |_| | | | 26 | | | +Attinyx5--------+ | |"| 2k2 |"| 2k2 27 | | +-----| Reset Vcc |-----' |_| |_| 28 | | | | | | 29 | _____ 0.1u | | | | 30 | _____ ,---------| SCL |-----------+-------|-----<> SCL 31 | | | | | | 32 | | | | | | 33 | | | --| |-- | 34 | | | | | | 35 | | | | | | 36 | +----|---+-----| GND SDA |-------------------+-----<> SDA 37 | | | +----------------+ 38 | | v GND 39 | | 40 | '-----------------------------------------------------> NeoPixel Data 41 | 42 | ``` 43 | 44 | ## Getting the code 45 | 46 | This project uses git submodules (I kinda wish it didn't...). You can clone 47 | it like so: 48 | 49 | ```git clone --recursive https://github.com/usedbytes/neopixel_i2c``` 50 | 51 | If your git version is too old to support that, do this instead: 52 | 53 | ``` 54 | git clone --recursive https://github.com/usedbytes/neopixel_i2c 55 | cd neopixel_i2c 56 | git submodule update --init --recursive 57 | ``` 58 | 59 | 60 | ## Basic Functionality 61 | 62 | There are two basic operating modes: 63 | * In *normal* mode, each LED is individually driven based on the value in its 64 | control register. 65 | * In *global* mode, all LEDs are driven to the same value, based on the values 66 | in the global value registers. 67 | 68 | The operating modes are selected by flipping the *GLB* bit in the **CTRL** 69 | register. 70 | 71 | ## i2c Protocol 72 | 73 | **The slave address is currently hardcoded to 0x40 in the firmware**, see 74 | 75 | ``` 76 | i2c/i2c_slave_defs.h:30 77 | ``` 78 | 79 | 80 | This utilises my i2c slave library (https://github.com/usedbytes/usi_i2c_slave) 81 | which means it follows a fairly standard i2c protocol (for more, see here: 82 | http://www.robot-electronics.co.uk/i2c-tutorial). 83 | 84 | Writes look like this: 85 | 86 | | Start | Slave Address << 1 | Register Address | Data | Stop | 87 | |-------|--------------------|------------------|------|------| 88 | 89 | The register address will auto-increment after every byte, so you can write 90 | data in bursts. 91 | 92 | Reads look like this: 93 | 94 | | Start | Slave Address | Register Address | Restart | (Slave Address << 1) + 1 | Data | Stop | 95 | |-------|---------------|------------------|---------|---------------------------|------|------| 96 | 97 | First you do a write transaction to set the register address to read from, then 98 | a read transaction to read the data. When you've read all the data you want, 99 | send a NAK after the last byte to terminate the read. 100 | 101 | **The LED values are only updated after a STOP is received** 102 | 103 | ## Register Map 104 | The register map consists of a number of global control registers - address 105 | 0x0-0x3 - followed by an array of registers which hold the individual value 106 | for each LED in normal mode. 107 | 108 | | **Address** | **Name** | **Description** | **Access** | **Reset** | 109 | |------------:|--------------|:---------------------|--------|------:| 110 | | 0x00 | **CTRL** | Control Register | R/W | 0 | 111 | | 0x01 | **GLB_G** | Global Green Value | R/W | 0 | 112 | | 0x02 | **GLB_R** | Global Red Value | R/W | 0 | 113 | | 0x03 | **GLB_B** | Global Blue Value | R/W | 0 | 114 | |Array follows|--------------|----------------------|--------|-------| 115 | | 0x04 | **GREEN[0]** | Green value, LED0 | R/W | 0 | 116 | | 0x05 | **RED[0]** | Red value, LED0 | R/W | 0 | 117 | | 0x06 | **BLUE[0]** | Blue value, LED0 | R/W | 0 | 118 | | .... | .... | .... | .... | .... | 119 | | (3*n) + 4 | **GREEN[n]** | Green value, LEDn | R/W | 0 | 120 | | (3*n) + 5 | **RED[n]** | Red value, LEDn | R/W | 0 | 121 | | (3*n) + 6 | **BLUE[n]** | Blue value, LEDn | R/W | 0 | 122 | 123 | ## Register Descriptions 124 | 125 | ### **CTRL** 126 | The control register sets the operating mode. 127 | 128 | | Name: | RSVD | RSVD | RSVD | RSVD | RSVD | RSVD | GLB | RST | 129 | |--------:|:----:|:----:|:----:|:----:|:----:|:----:|:----:|:----:| 130 | | Bit: | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 131 | | Access: | r | r | r | r | r | r | rw | rw | 132 | 133 | #### *RST* 134 | Writing a 1 to this bit will reset the LED controler, setting all LEDs to OFF 135 | 136 | This bit will be automatically cleared once the reset has completed. 137 | 138 | #### *GLB* 139 | Writing a one to this bit causes the global color value to be displayed on all 140 | LEDs at the end of the transaction - Normally you would set the **GLB_R**, 141 | **GLB_G**, and **GLB_B** values in the same transaction as setting the *GLB* 142 | bit so that the new colour is immediately applied. 143 | 144 | Writing a zero to this bit will disable the global colour override and return to 145 | normal operation. 146 | 147 | ### **GLB_R**, **GLB_G**, **GLB_B** 148 | These registers hold the global colour value. When the *GLB* bit in the 149 | **CTRL** register is set, all LEDs will display this colour. 150 | 151 | ### **LED Value Array** 152 | Everything after the global registers is an array of data for each LED. 153 | When the *GLB* bit is not set, each LED will display whatever value is 154 | programmed in its corresponding register set. 155 | -------------------------------------------------------------------------------- /main.c: -------------------------------------------------------------------------------- 1 | /* 2 | * Neopixel I2C Slave application 3 | * 4 | * At boot, scrolls a bright spot (init_color) along the array 5 | * Will stop as soon as an i2c transaction is received 6 | */ 7 | 8 | #include 9 | #include 10 | #include 11 | #include 12 | #include 13 | #include 14 | #include 15 | 16 | volatile uint8_t i2c_reg[I2C_N_REG]; 17 | const uint8_t init_color[3] PROGMEM = { 0x00, 0xFF, 0x00 }; 18 | 19 | static inline void set_leds_global(void) 20 | { 21 | ws2812_setleds_constant((struct cRGB *)®_GLB_G, N_LEDS); 22 | } 23 | 24 | static inline void update_leds(void) 25 | { 26 | ws2812_sendarray(i2c_reg + I2C_N_GLB_REG, N_LEDS * 3); 27 | } 28 | 29 | void do_reset(void) 30 | { 31 | char i = N_LEDS * 3; 32 | volatile uint8_t *p = i2c_reg + I2C_N_GLB_REG; 33 | 34 | cli(); 35 | REG_GLB_G = 0; 36 | REG_GLB_R = 0; 37 | REG_GLB_B = 0; 38 | ws2812_setleds_constant((struct cRGB *)®_GLB_G, N_LEDS); 39 | REG_GLB_G = pgm_read_byte(init_color); 40 | REG_GLB_R = pgm_read_byte(init_color + 1); 41 | REG_GLB_B = pgm_read_byte(init_color + 2); 42 | REG_CTRL = 0; 43 | 44 | /* Reset the registers or we'll just go back to the old values! */ 45 | while (i--) { 46 | *p = 0; 47 | p++; 48 | } 49 | 50 | sei(); 51 | } 52 | 53 | void swirly(void) 54 | { 55 | uint8_t led = N_LEDS; 56 | volatile uint8_t *p = i2c_reg + I2C_N_GLB_REG + (N_LEDS * 3); 57 | uint8_t g = pgm_read_byte(init_color); 58 | uint8_t r = pgm_read_byte(init_color + 1); 59 | uint8_t b = pgm_read_byte(init_color + 2); 60 | uint8_t tmp; 61 | 62 | /* Initialise a bright spot with a tail: 63 | * { 255, 127, 63, 31, 15, 15, 15, 15 ... } 64 | */ 65 | while (led--) { 66 | *(--p) = b; 67 | if (b & 0xf0) 68 | b >>= 1; 69 | 70 | *(--p) = r; 71 | if (r & 0xf0) 72 | r >>= 1; 73 | 74 | *(--p) = g; 75 | if (g & 0xf0) 76 | g >>= 1; 77 | 78 | } 79 | 80 | /* Shuffle the bright spot along */ 81 | g = pgm_read_byte(init_color); 82 | r = pgm_read_byte(init_color + 1); 83 | b = pgm_read_byte(init_color + 2); 84 | while (1) 85 | { 86 | update_leds(); 87 | 88 | led = N_LEDS; 89 | p = &i2c_reg[I2C_N_GLB_REG]; 90 | while (led--) { 91 | tmp = *p; 92 | *(p++) = g; 93 | if (led) 94 | g = tmp; 95 | 96 | tmp = *p; 97 | *(p++) = r; 98 | if (led) 99 | r = tmp; 100 | 101 | tmp = *p; 102 | *(p++) = b; 103 | if (led) 104 | b = tmp; 105 | } 106 | 107 | /* As soon as there's a transaction to handle, bail out */ 108 | tmp = 70; 109 | while (tmp--) { 110 | if (i2c_check_stop()) 111 | return; 112 | _delay_ms(1); 113 | } 114 | } 115 | } 116 | 117 | int main(void) 118 | { 119 | DDRB = (1 << 3); 120 | 121 | i2c_init(); 122 | sei(); 123 | 124 | swirly(); 125 | goto inner; 126 | 127 | while(1) 128 | { 129 | if (i2c_check_stop()) { 130 | inner: 131 | if (REG_CTRL & CTRL_RST) 132 | do_reset(); 133 | else if (REG_CTRL & CTRL_GLB) 134 | set_leds_global(); 135 | else 136 | update_leds(); 137 | } 138 | } 139 | } 140 | --------------------------------------------------------------------------------