stm32/i2cslave: Add functions to read/write I2C data.

Instead of requiring the callback to consume/provide the data.  This allows
the data to be consumed/provided later on, which will stretch the I2C clock
until that occurs.

Signed-off-by: Damien George <[email protected]>

Author: dpgeorge

ports/stm32/i2cslave.c

@@ -45,10 +45,12 @@ void i2c_slave_irq_handler(i2c_slave_t *i2c) {
         i2c_slave_process_addr_match(i2c, (sr2 >> I2C_SR2_TRA_Pos) & 1);
     }
     if (sr1 & I2C_SR1_TXE) {
-        i2c->DR = i2c_slave_process_tx_byte(i2c);
+        // This callback must call i2c_slave_write_byte.
+        i2c_slave_process_tx_byte(i2c);
     }
     if (sr1 & I2C_SR1_RXNE) {
-        i2c_slave_process_rx_byte(i2c, i2c->DR);
+        // This callback must call i2c_slave_read_byte.
+        i2c_slave_process_rx_byte(i2c);
     }
     if (sr1 & I2C_SR1_STOPF) {
         // STOPF only set at end of RX mode (in TX mode AF is set on NACK)
@@ -80,10 +82,12 @@ void i2c_slave_irq_handler(i2c_slave_t *i2c) {
         i2c_slave_process_addr_match(i2c, (i2c->ISR >> I2C_ISR_DIR_Pos) & 1);
     }
     if (isr & I2C_ISR_TXIS) {
-        i2c->TXDR = i2c_slave_process_tx_byte(i2c);
+        // This callback must call i2c_slave_write_byte.
+        i2c_slave_process_tx_byte(i2c);
     }
     if (isr & I2C_ISR_RXNE) {
-        i2c_slave_process_rx_byte(i2c, i2c->RXDR);
+        // This callback must call i2c_slave_read_byte.
+        i2c_slave_process_rx_byte(i2c);
     }
     if (isr & I2C_ISR_STOPF) {
         // STOPF only set for STOP condition, not a repeated START

ports/stm32/i2cslave.h

@@ -28,6 +28,8 @@
 
 #include STM32_HAL_H
 
+#if defined(STM32F4) || defined(STM32F7) || defined(STM32H7) || defined(STM32WB)
+
 #if !defined(I2C2_BASE)
 // This MCU doesn't have I2C2_BASE, define it so that the i2c_idx calculation works.
 #define I2C2_BASE (I2C1_BASE + ((I2C3_BASE - I2C1_BASE) / 2))
@@ -78,13 +80,31 @@ static inline void i2c_slave_shutdown(i2c_slave_t *i2c, int irqn) {
     NVIC_DisableIRQ(irqn);
 }
 
+static inline void i2c_slave_write_byte(i2c_slave_t *i2c, uint8_t value) {
+    #if defined(STM32F4)
+    i2c->DR = value;
+    #else
+    i2c->TXDR = value;
+    #endif
+}
+
+static inline uint8_t i2c_slave_read_byte(i2c_slave_t *i2c) {
+    #if defined(STM32F4)
+    return i2c->DR;
+    #else
+    return i2c->RXDR;
+    #endif
+}
+
 void i2c_slave_irq_handler(i2c_slave_t *i2c);
 
 // These should be provided externally
 int i2c_slave_process_addr_match(i2c_slave_t *i2c, int rw);
-int i2c_slave_process_rx_byte(i2c_slave_t *i2c, uint8_t val);
+int i2c_slave_process_rx_byte(i2c_slave_t *i2c);
 void i2c_slave_process_rx_end(i2c_slave_t *i2c);
-uint8_t i2c_slave_process_tx_byte(i2c_slave_t *i2c);
+void i2c_slave_process_tx_byte(i2c_slave_t *i2c);
 void i2c_slave_process_tx_end(i2c_slave_t *i2c);
 
+#endif
+
 #endif // MICROPY_INCLUDED_STM32_I2CSLAVE_H

ports/stm32/mboot/main.c

@@ -805,9 +805,9 @@ int i2c_slave_process_addr_match(i2c_slave_t *i2c, int rw) {
     return 0; // ACK
 }
 
-int i2c_slave_process_rx_byte(i2c_slave_t *i2c, uint8_t val) {
+int i2c_slave_process_rx_byte(i2c_slave_t *i2c) {
     if (i2c_obj.cmd_buf_pos < sizeof(i2c_obj.cmd_buf)) {
-        i2c_obj.cmd_buf[i2c_obj.cmd_buf_pos++] = val;
+        i2c_obj.cmd_buf[i2c_obj.cmd_buf_pos++] = i2c_slave_read_byte(i2c);
     }
     return 0; // ACK
 }
@@ -909,15 +909,17 @@ void i2c_slave_process_rx_end(i2c_slave_t *i2c) {
     i2c_obj.cmd_arg_sent = false;
 }
 
-uint8_t i2c_slave_process_tx_byte(i2c_slave_t *i2c) {
+void i2c_slave_process_tx_byte(i2c_slave_t *i2c) {
+    uint8_t value;
     if (i2c_obj.cmd_send_arg) {
         i2c_obj.cmd_arg_sent = true;
-        return i2c_obj.cmd_arg;
+        value = i2c_obj.cmd_arg;
     } else if (i2c_obj.cmd_buf_pos < sizeof(i2c_obj.cmd_buf)) {
-        return i2c_obj.cmd_buf[i2c_obj.cmd_buf_pos++];
+        value = i2c_obj.cmd_buf[i2c_obj.cmd_buf_pos++];
     } else {
-        return 0;
+        value = 0;
     }
+    i2c_slave_write_byte(i2c, value);
 }
 
 void i2c_slave_process_tx_end(i2c_slave_t *i2c) {