re-implement deferred I2C handlers for the Arduino pbdrv drv

1 files changed, 39 insertions, 12 deletions

diff --git a/lib/pbdrv/drv/arduino/mod.cpp b/lib/pbdrv/drv/arduino/mod.cpp
index d2a6402..c381077 100644
--- a/lib/pbdrv/drv/arduino/mod.cpp
+++ b/lib/pbdrv/drv/arduino/mod.cpp
@@ -1,22 +1,33 @@
-#ifndef ARDUINO
-#error This driver only works on the Arduino platform!
-#endif
-
 #include <Arduino.h>
 #include <Wire.h>
 #include <avr/delay.h>
 
+#include <FreeRTOS.h>
+#include <timers.h>
+#include <task.h>
+
 #include "../../pb.h"
 #include "../../pb-mod.h"
 #include "../../pb-types.h"
+#include "../../pb-buf.h"
+#include "../../pb-mem.h"
+
+static void async_pb_i2c_recv(void * _msg, uint32_t _) {
+	pb_buf_t * msg = (pb_buf_t *) _msg;
+	pb_i2c_recv((uint8_t *) msg->data, msg->size);
+	pb_buf_free(msg);
+	pb_free(msg);
+}
 
 static void recv_event(int bytes) {
-	uint8_t data[bytes];
-	size_t sz = 0;
+	pb_buf_t * msg = (pb_buf_t *) pb_malloc(sizeof(pb_buf_t));
+	msg->data = (char *) pb_malloc(bytes);
+	msg->size = 0;
 	while (Wire.available())
-		data[sz++] = Wire.read();
+		msg->data[msg->size++] = Wire.read();
 
-	pb_i2c_recv(data, sz);
+	// defer pb_i2c_recv call
+	xTimerPendFunctionCallFromISR(async_pb_i2c_recv, msg, 0, NULL);
 }
 
 static void pb_setup() {
@@ -27,7 +38,17 @@ static void pb_setup() {
 	Wire.onReceive(recv_event);
 }
 
+/**
+ * \ingroup pb_drv_arduino
+ * \warning This function includes a hard-coded 10ms delay before sending. This
+ * is to work around a weird issue where the Arduino pulls both SDA and SCL low
+ * while attempting to initiate an I2C transmission. We were able to verify
+ * that the Arduino correctly handles bus arbitration under a test scenario
+ * with 2 Uno's, but ran into issues while integrating the Arduino's with the
+ * RP2040.
+ */
 __weak void pb_i2c_send(i2c_addr_t addr, const uint8_t * buf, size_t sz) {
+	vTaskDelay(10 / portTICK_PERIOD_MS); // prevent bus collisions
 	Wire.beginTransmission((int) addr);
 	Wire.write(buf, sz);
 	Wire.endTransmission(true);
@@ -41,6 +62,14 @@ extern void loop(void);
 //! Arduino internal initialization
 void init(void);
 
+//! FreeRTOS loop task
+void loop_task() {
+	for(;;) {
+		loop();
+		if (serialEventRun) serialEventRun();
+	}
+}
+
 /**
  * \ingroup pb_drv_arduino
  * \brief Application entrypoint
@@ -59,10 +88,8 @@ int main(void) {
 	init(); // call arduino internal setup
 	setup(); // call regular arduino setup
 	pb_setup(); // call pbdrv-mod setup
-	for(;;) {
-		loop();
-		if (serialEventRun) serialEventRun();
-	}
+	xTaskCreate((TaskFunction_t) loop_task, "loop", configMINIMAL_STACK_SIZE, NULL, tskIDLE_PRIORITY + 1, NULL);
+	vTaskStartScheduler(); // start freertos scheduler
 	return 0;
 }