mbed: add stm32 i2c patch

Author: facchinm

patches/0206-STM32-Fix-repeated-start-for-transactional-i2c.patch

@@ -0,0 +1,46 @@
+From e7fb3b80769ec498d1dcaa9421caaa19ed7975ca Mon Sep 17 00:00:00 2001
+From: Jamie Smith <[email protected]>
+Date: Mon, 20 Mar 2023 21:05:20 -0700
+Subject: [PATCH] Fix repeated start for transactional I2C API on STM32 devices
+ with I2C v2
+
+---
+ targets/TARGET_STM/i2c_api.c | 24 ++++++++++--------------
+ 1 file changed, 10 insertions(+), 14 deletions(-)
+
+diff --git a/targets/TARGET_STM/i2c_api.c b/targets/TARGET_STM/i2c_api.c
+index 6ba7fcc6496..266eeaa5772 100644
+--- a/targets/TARGET_STM/i2c_api.c
++++ b/targets/TARGET_STM/i2c_api.c
+@@ -931,21 +931,17 @@ static void prep_for_restart_if_needed(struct i2c_s *obj_s) {
+  * STOP at the end of the current transaction.
+  */
+ static uint32_t get_hal_xfer_options(struct i2c_s *obj_s, bool stop) {
+-    if (obj_s->state == STM_I2C_SB_READ_IN_PROGRESS || obj_s->state == STM_I2C_SB_WRITE_IN_PROGRESS) {
+-        if(stop) {
+-            // Generate restart condition and stop at end
+-            return I2C_OTHER_AND_LAST_FRAME;
+-        } else {
+-            // Generate restart condition but don't send STOP
+-            return I2C_OTHER_FRAME;
+-        }
++    (void)obj_s;
++
++    // Note: The naming used by STM32 HAL is quite counterintuitive.  "OTHER_FRAME" means "always send a
++    // start/restart condition at the start of the frame".  In contrast, "FIRST_FRAME" means "don't send
++    // a start/restart if the previous transfer was going the same direction".
++    if(stop) {
++        // Generate start condition and stop at end
++        return I2C_OTHER_AND_LAST_FRAME;
+     } else {
+-        if(stop) {
+-            // Generate start condition and stop at end
+-            return I2C_FIRST_AND_LAST_FRAME;
+-        } else {
+-            return I2C_LAST_FRAME;
+-        }
++        // Generate only the start condition
++        return I2C_OTHER_FRAME;
+     }
+ }
+