From 7be4a23c0cccbcd9096d57235f32c5c2e02f6604 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Fri, 15 Jun 2018 14:15:31 +1000
Subject: [PATCH] stm32/i2cslave: Fix ordering of event callbacks in slave IRQ
 handler.

It's possible (at least on F4 MCU's) to have RXNE and STOPF set at the same
time during a call to the slave IRQ handler.  In such cases RXNE should be
handled before STOPF so that all bytes are processed before
i2c_slave_process_rx_end() is called.
---
 ports/stm32/i2cslave.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/ports/stm32/i2cslave.c b/ports/stm32/i2cslave.c
index f8ff19cd6..473f0c8c5 100644
--- a/ports/stm32/i2cslave.c
+++ b/ports/stm32/i2cslave.c
@@ -44,6 +44,12 @@ void i2c_slave_ev_irq_handler(i2c_slave_t *i2c) {
         uint32_t sr2 = i2c->SR2;
         i2c_slave_process_addr_match((sr2 >> I2C_SR2_TRA_Pos) & 1);
     }
+    if (sr1 & I2C_SR1_TXE) {
+        i2c->DR = i2c_slave_process_tx_byte();
+    }
+    if (sr1 & I2C_SR1_RXNE) {
+        i2c_slave_process_rx_byte(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
@@ -52,12 +58,6 @@ void i2c_slave_ev_irq_handler(i2c_slave_t *i2c) {
         i2c_slave_process_rx_end();
         i2c->CR1 |= I2C_CR1_ACK;
     }
-    if (sr1 & I2C_SR1_TXE) {
-        i2c->DR = i2c_slave_process_tx_byte();
-    }
-    if (sr1 & I2C_SR1_RXNE) {
-        i2c_slave_process_rx_byte(i2c->DR);
-    }
 }
 
 #elif defined(STM32F7)
@@ -79,6 +79,12 @@ void i2c_slave_ev_irq_handler(i2c_slave_t *i2c) {
         i2c->ICR = I2C_ICR_ADDRCF;
         i2c_slave_process_addr_match(0);
     }
+    if (isr & I2C_ISR_TXIS) {
+        i2c->TXDR = i2c_slave_process_tx_byte();
+    }
+    if (isr & I2C_ISR_RXNE) {
+        i2c_slave_process_rx_byte(i2c->RXDR);
+    }
     if (isr & I2C_ISR_STOPF) {
         // STOPF only set for STOP condition, not a repeated START
         i2c->ICR = I2C_ICR_STOPCF;
@@ -90,12 +96,6 @@ void i2c_slave_ev_irq_handler(i2c_slave_t *i2c) {
         }
         i2c->OAR1 |= I2C_OAR1_OA1EN;
     }
-    if (isr & I2C_ISR_TXIS) {
-        i2c->TXDR = i2c_slave_process_tx_byte();
-    }
-    if (isr & I2C_ISR_RXNE) {
-        i2c_slave_process_rx_byte(i2c->RXDR);
-    }
 }
 
 #endif