raspberrypi/I2CTarget: Fixed bug where I2C starts were seen as restarts.

The Rasperry Pi Pico, based on the RP2040, has a register that maintains
the status of I2C interrupt flags called IC_INTR_STAT. The bits of this
register are set by hardware and cleared by software. Before this commit,
the I2CTarget library did not clear the restart bit (R_RESTART_DET) in
this register after an I2C transaction ended, causing the is_restart
field of the i2ctarget_i2c_target_request_obj_t struct to always be true
after the first I2C transaction. This commit causes the restart and stop
bits to get cleared when the I2C transaction ends.

Signed-off-by: Amaar Ebrahim <[email protected]>

Author: MarkEbrahim

ports/raspberrypi/common-hal/i2ctarget/I2CTarget.c

@@ -85,6 +85,8 @@ void common_hal_i2ctarget_i2c_target_deinit(i2ctarget_i2c_target_obj_t *self) {
 }
 
 int common_hal_i2ctarget_i2c_target_is_addressed(i2ctarget_i2c_target_obj_t *self, uint8_t *address, bool *is_read, bool *is_restart) {
+    common_hal_i2ctarget_i2c_target_is_stop(self);
+
     if (!((self->peripheral->hw->raw_intr_stat & I2C_IC_INTR_STAT_R_RX_FULL_BITS) || (self->peripheral->hw->raw_intr_stat & I2C_IC_INTR_STAT_R_RD_REQ_BITS))) {
         return 0;
     }
@@ -123,6 +125,19 @@ int common_hal_i2ctarget_i2c_target_write_byte(i2ctarget_i2c_target_obj_t *self,
     }
 }
 
+int common_hal_i2ctarget_i2c_target_is_stop(i2ctarget_i2c_target_obj_t *self) {
+    // Interrupt bits must be cleared by software. Clear the STOP and
+    // RESTART interrupt bits after an I2C transaction finishes.
+    if (self->peripheral->hw->raw_intr_stat & I2C_IC_INTR_STAT_R_STOP_DET_BITS) {
+        self->peripheral->hw->clr_stop_det;
+        self->peripheral->hw->clr_restart_det;
+        return 1;
+    } else {
+        return 0;
+    }
+
+}
+
 void common_hal_i2ctarget_i2c_target_ack(i2ctarget_i2c_target_obj_t *self, bool ack) {
     return;
 }

ports/raspberrypi/common-hal/i2ctarget/I2CTarget.h

@@ -21,3 +21,5 @@ typedef struct {
     uint8_t scl_pin;
     uint8_t sda_pin;
 } i2ctarget_i2c_target_obj_t;
+
+int common_hal_i2ctarget_i2c_target_is_stop(i2ctarget_i2c_target_obj_t *self);