refactor to remove common_hal_i2ctarget_i2c_target_is_stop(). Fix separate issue with read_byte returning early.

Author: FoamyGuy

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

@@ -85,7 +85,12 @@ 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);
+    // 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;
+    }
 
     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;
@@ -100,12 +105,20 @@ int common_hal_i2ctarget_i2c_target_is_addressed(i2ctarget_i2c_target_obj_t *sel
 }
 
 int common_hal_i2ctarget_i2c_target_read_byte(i2ctarget_i2c_target_obj_t *self, uint8_t *data) {
-    if (self->peripheral->hw->status & I2C_IC_STATUS_RFNE_BITS) {
-        *data = (uint8_t)self->peripheral->hw->data_cmd;
-        return 1;
-    } else {
-        return 0;
+    // Wait for data to arrive or a STOP condition indicating the transfer is over.
+    // Without this wait, the CPU can drain the FIFO faster than bytes arrive on the
+    // I2C bus, causing transfers to be split into multiple partial reads.
+    for (int t = 0; t < 100; t++) {
+        if (self->peripheral->hw->status & I2C_IC_STATUS_RFNE_BITS) {
+            *data = (uint8_t)self->peripheral->hw->data_cmd;
+            return 1;
+        }
+        if (self->peripheral->hw->raw_intr_stat & I2C_IC_INTR_STAT_R_STOP_DET_BITS) {
+            break;
+        }
+        mp_hal_delay_us(10);
     }
+    return 0;
 }
 
 int common_hal_i2ctarget_i2c_target_write_byte(i2ctarget_i2c_target_obj_t *self, uint8_t data) {
@@ -125,19 +138,6 @@ 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

@@ -21,5 +21,3 @@ 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);