From e638defff453102d5d0811f7b9a596682a21e9af Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Wed, 9 May 2018 15:53:09 +1000
Subject: [PATCH] stm32/i2c: Make sure stop condition is sent after receiving
 addr nack.

---
 ports/stm32/i2c.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ports/stm32/i2c.c b/ports/stm32/i2c.c
index 7421ae1bd2..63bd09ae5f 100644
--- a/ports/stm32/i2c.c
+++ b/ports/stm32/i2c.c
@@ -113,7 +113,8 @@ int i2c_start_addr(i2c_t *i2c, int rd_wrn, uint16_t addr, size_t len, bool stop)
 
     // Check if the slave responded or not
     if (i2c->ISR & I2C_ISR_NACKF) {
-        // If we get a NACK then I2C periph releases the bus, so don't send STOP
+        // If we get a NACK then I2C periph unconditionally sends a STOP
+        i2c_wait_isr_set(i2c, I2C_ISR_STOPF); // Don't leak errors from this call
         i2c->CR1 &= ~I2C_CR1_PE;
         return -MP_ENODEV;
     }