134 |
135 |
Modes of Operation
136 |
A mode of operation specifies how Céu-Arduino captures events from the
137 | environment (e.g., pin changes) and redirects them to the Céu application.
138 |
Céu-Arduino supports the polling and interrupt-based modes of operation.
139 |
The polling mode is the default mode of operation.
140 |
The modes of operation are implemented in C and are part of Céu-Arduino.
141 | Each mode is described in pseudo-code as follows.
142 |
Polling
143 |
The polling mode of Céu-Arduino continually checks for changes in the
144 | environment in an infinite loop:
145 |
void setup () {
146 | ceu_start();
147 | while (<program-is-running>) {
148 | ceu_input(CEU_INPUT__NONE, NULL, <time>); /* input async and timer */
149 | if (<pin-*-changed>) {
150 | ceu_input(CEU_INPUT__PIN_*, <...>); /* input pins */
151 | }
152 | <...> // for each pin
153 | }
154 | ceu_stop();
155 | while (1); /* freezes arduino */
156 | }
157 |
158 | void loop () { /* never reached */ }
159 |
160 |
161 |
The inputs are polled on each loop iteration and changes are notified to the
162 | Céu application through ceu_input calls.
163 |
The polling mode uses 100% of the CPU time.
164 |
165 |
Currently, the polling mode supports the following input events:
166 |
167 | - Timers
168 | - Asynchronous blocks
169 | - Digital pins
170 |
171 |
Compilation
172 |
Since polling is the default mode of operation, compilation only needs to
173 | provide the Céu application:
174 |
$ make CEU_SRC=<path-to-ceu-application>
175 |
176 |
177 |
Interrupts
178 |
In the interrupt-based mode of Céu-Arduino, all input is done in Céu itself
179 | through async/isr blocks.
180 | Emitting an input event from an async/isr only sets a flag which is then
181 | checked in the Arduino loop:
182 |
void setup () {
183 | ceu_start();
184 | while (<program-is-running>) {
185 | ceu_input(CEU_INPUT__NONE, NULL, CEU_WCLOCK_INACTIVE);
186 | if (<any-isr-evt-occurred>) { // interrupts off
187 | ceu_input(<isr-evt-occuring>, <...>); // interrupts on
188 | }
189 | #ifdef CEU_FEATURES_ISR_SLEEP
190 | else if (!<program-has-pending-async>) {
191 | <enter-sleep-mode>
192 | }
193 | #endif
194 | }
195 | ceu_stop();
196 | while (1); /* freezes arduino */
197 | }
198 |
199 | void loop () { /* never reached */ }
200 |
201 |
202 |
To comply with the synchronous semantics of Céu, all ceu_input calls are
203 | serialized in the loop.
204 |
If the macro CEU_FEATURES_ISR_SLEEP is defined, the Arduino enters in the
205 | SLEEP_MODE_IDLE
206 | sleep mode
207 | after each reaction.
208 |
Interrupts are disabled only while checking for occurring inputs.
209 | Hence, async/isr blocks and synchronous code may be concurrent and require
210 | atomic blocks.
211 |
An async/isr in Céu-Arduino requires two arguments:
212 |
213 | - the interrupt number (i.e., the index in the interrupt vector)
214 | - the interrupt trigger mode (i.e., when the interrupt should be triggered)
215 |
216 |
The interrupt trigger mode is only used for digital pin interrupts:
217 |
https://www.arduino.cc/en/Reference/AttachInterrupt
218 |
The example that follows executes the code marked as <...> whenever the value
219 | of pin 2 changes:
220 |
spawn async/isr [_digitalPinToInterrupt(2),_CHANGE] do
221 | <...>
222 | end
223 |
224 |
225 |
226 |
Drivers:
227 |
235 |
Compilation
236 |
Applications that use interrupts have to be compiled with CEU_ISR=true:
237 |
$ make CEU_ISR=true CEU_SRC=<path-to-ceu-application>
238 |
239 |
240 |