diff --git a/ports/stm32/i2cslave.c b/ports/stm32/i2cslave.c
index 149e105ee8..a575c53085 100644
--- a/ports/stm32/i2cslave.c
+++ b/ports/stm32/i2cslave.c
@@ -42,20 +42,20 @@ void i2c_slave_ev_irq_handler(i2c_slave_t *i2c) {
         // Read of SR1, SR2 needed to clear ADDR bit
         sr1 = i2c->SR1;
         uint32_t sr2 = i2c->SR2;
-        i2c_slave_process_addr_match((sr2 >> I2C_SR2_TRA_Pos) & 1);
+        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->DR = i2c_slave_process_tx_byte(i2c);
     }
     if (sr1 & I2C_SR1_RXNE) {
-        i2c_slave_process_rx_byte(i2c->DR);
+        i2c_slave_process_rx_byte(i2c, i2c->DR);
     }
     if (sr1 & I2C_SR1_STOPF) {
         // STOPF only set at end of RX mode (in TX mode AF is set on NACK)
         // Read of SR1, write CR1 needed to clear STOPF bit
         sr1 = i2c->SR1;
         i2c->CR1 &= ~I2C_CR1_ACK;
-        i2c_slave_process_rx_end();
+        i2c_slave_process_rx_end(i2c);
         i2c->CR1 |= I2C_CR1_ACK;
     }
 }
@@ -77,22 +77,22 @@ void i2c_slave_ev_irq_handler(i2c_slave_t *i2c) {
         // Set TXE so that TXDR is flushed and ready for the first byte
         i2c->ISR = I2C_ISR_TXE;
         i2c->ICR = I2C_ICR_ADDRCF;
-        i2c_slave_process_addr_match(0);
+        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->TXDR = i2c_slave_process_tx_byte(i2c);
     }
     if (isr & I2C_ISR_RXNE) {
-        i2c_slave_process_rx_byte(i2c->RXDR);
+        i2c_slave_process_rx_byte(i2c, i2c->RXDR);
     }
     if (isr & I2C_ISR_STOPF) {
         // STOPF only set for STOP condition, not a repeated START
         i2c->ICR = I2C_ICR_STOPCF;
         i2c->OAR1 &= ~I2C_OAR1_OA1EN;
         if (i2c->ISR & I2C_ISR_DIR) {
-            // i2c_slave_process_tx_end();
+            i2c_slave_process_tx_end(i2c);
         } else {
-            i2c_slave_process_rx_end();
+            i2c_slave_process_rx_end(i2c);
         }
         i2c->OAR1 |= I2C_OAR1_OA1EN;
     }
diff --git a/ports/stm32/i2cslave.h b/ports/stm32/i2cslave.h
index f335c92912..4a51bf378e 100644
--- a/ports/stm32/i2cslave.h
+++ b/ports/stm32/i2cslave.h
@@ -67,9 +67,10 @@ static inline void i2c_slave_shutdown(i2c_slave_t *i2c, int irqn) {
 void i2c_slave_ev_irq_handler(i2c_slave_t *i2c);
 
 // These should be provided externally
-int i2c_slave_process_addr_match(int rw);
-int i2c_slave_process_rx_byte(uint8_t val);
-void i2c_slave_process_rx_end(void);
-uint8_t i2c_slave_process_tx_byte(void);
+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);
+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_end(i2c_slave_t *i2c);
 
 #endif // MICROPY_INCLUDED_STM32_I2CSLAVE_H
diff --git a/ports/stm32/mboot/main.c b/ports/stm32/mboot/main.c
index b3e63ccc26..87618e7f41 100644
--- a/ports/stm32/mboot/main.c
+++ b/ports/stm32/mboot/main.c
@@ -664,7 +664,7 @@ void i2c_init(int addr) {
     i2c_slave_init(MBOOT_I2Cx, I2Cx_EV_IRQn, IRQ_PRI_I2C, addr);
 }
 
-int i2c_slave_process_addr_match(int rw) {
+int i2c_slave_process_addr_match(i2c_slave_t *i2c, int rw) {
     if (i2c_obj.cmd_arg_sent) {
         i2c_obj.cmd_send_arg = false;
     }
@@ -672,14 +672,14 @@ int i2c_slave_process_addr_match(int rw) {
     return 0; // ACK
 }
 
-int i2c_slave_process_rx_byte(uint8_t val) {
+int i2c_slave_process_rx_byte(i2c_slave_t *i2c, uint8_t val) {
     if (i2c_obj.cmd_buf_pos < sizeof(i2c_obj.cmd_buf)) {
         i2c_obj.cmd_buf[i2c_obj.cmd_buf_pos++] = val;
     }
     return 0; // ACK
 }
 
-void i2c_slave_process_rx_end(void) {
+void i2c_slave_process_rx_end(i2c_slave_t *i2c) {
     if (i2c_obj.cmd_buf_pos == 0) {
         return;
     }
@@ -764,7 +764,7 @@ void i2c_slave_process_rx_end(void) {
     i2c_obj.cmd_arg_sent = false;
 }
 
-uint8_t i2c_slave_process_tx_byte(void) {
+uint8_t i2c_slave_process_tx_byte(i2c_slave_t *i2c) {
     if (i2c_obj.cmd_send_arg) {
         i2c_obj.cmd_arg_sent = true;
         return i2c_obj.cmd_arg;
@@ -775,6 +775,9 @@ uint8_t i2c_slave_process_tx_byte(void) {
     }
 }
 
+void i2c_slave_process_tx_end(i2c_slave_t *i2c) {
+}
+
 #endif // defined(MBOOT_I2C_SCL)
 
 /******************************************************************************/