I2C - unify i2cUnstick implementation, improve unstick a bit (#13541)

* I2C - unify i2cUnstick implemntation, improve unstick a bit

Three copies were spread in I2C implementations.

- i2cUnstick is a bit more carefull about clock stretching
- bus status is returned (return true when bus in idle state)

* fixup! I2C - unify i2cUnstick implemntation, improve unstick a bit

* fixup! I2C - unify i2cUnstick implemntation, improve unstick a bit

---------

Co-authored-by: Petr Ledvina <ledvinap@hp124.ekotip.cz>

mk/source.mk

@@ -19,6 +19,7 @@ COMMON_SRC = \
             drivers/bus.c \
             drivers/bus_i2c_config.c \
             drivers/bus_i2c_busdev.c \
+            drivers/bus_i2c_utils.c \
             drivers/bus_i2c_soft.c \
             drivers/bus_octospi.c \
             drivers/bus_quadspi.c \

src/main/drivers/at32/bus_i2c_atbsp_init.c

@@ -27,7 +27,6 @@
 #if defined(USE_I2C) && !defined(SOFT_I2C)
 
 #include "drivers/io.h"
-#include "drivers/io_impl.h"
 #include "drivers/nvic.h"
 #include "drivers/time.h"
 #include "drivers/rcc.h"
@@ -35,22 +34,10 @@
 #include "drivers/bus_i2c.h"
 #include "drivers/bus_i2c_impl.h"
 #include "drivers/bus_i2c_timing.h"
+#include "drivers/bus_i2c_utils.h"
 
 #include "pg/pinio.h"
 
-// Number of bits in I2C protocol phase
-#define LEN_ADDR 7
-#define LEN_RW 1
-#define LEN_ACK 1
-
-// Clock period in us during unstick transfer
-#define UNSTICK_CLK_US 10
-
-// Allow 500us for clock strech to complete during unstick
-#define UNSTICK_CLK_STRETCH (500/UNSTICK_CLK_US)
-
-static void i2cUnstick(IO_t scl, IO_t sda);
-
 #define IOCFG_I2C_PU IO_CONFIG(GPIO_MODE_MUX , GPIO_DRIVE_STRENGTH_STRONGER, GPIO_OUTPUT_OPEN_DRAIN , GPIO_PULL_UP)
 #define IOCFG_I2C    IO_CONFIG(GPIO_MODE_MUX , GPIO_DRIVE_STRENGTH_STRONGER, GPIO_OUTPUT_OPEN_DRAIN , GPIO_PULL_NONE)
 
@@ -169,36 +156,4 @@ void i2cInit(I2CDevice device)
     i2c_enable(i2cx, TRUE);
 }
 
-static void i2cUnstick(IO_t scl, IO_t sda)
-{
-    int i;
-
-    IOHi(scl);
-    IOHi(sda);
-
-    IOConfigGPIO(scl, IOCFG_OUT_OD);
-    IOConfigGPIO(sda, IOCFG_OUT_OD);
-
-    for (i = 0; i < (LEN_ADDR + LEN_RW + LEN_ACK); i++) {
-        int timeout = UNSTICK_CLK_STRETCH;
-        while (!IORead(scl) && timeout) {
-            delayMicroseconds(UNSTICK_CLK_US);
-            timeout--;
-        }
-
-        IOLo(scl);
-        delayMicroseconds(UNSTICK_CLK_US / 2);
-        IOHi(scl);
-        delayMicroseconds(UNSTICK_CLK_US / 2);
-    }
-
-    IOLo(scl);
-    delayMicroseconds(UNSTICK_CLK_US / 2);
-    IOLo(sda);
-    delayMicroseconds(UNSTICK_CLK_US / 2);
-
-    IOHi(scl);
-    delayMicroseconds(UNSTICK_CLK_US / 2);
-    IOHi(sda);
-}
 #endif

src/main/drivers/bus_i2c_utils.c

@@ -0,0 +1,89 @@
+/*
+ * This file is part of Betaflight.
+ *
+ * Betaflight is free software. You can redistribute this software
+ * and/or modify this software under the terms of the GNU General
+ * Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * Betaflight is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this software.
+ *
+ * If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdbool.h>
+
+#include "platform.h"
+
+#include "drivers/io.h"
+#include "drivers/time.h"
+
+#include "bus_i2c_utils.h"
+
+// Clock period in us during unstick transfer
+#define UNSTICK_CLK_US 10  // 100Khz
+// Allow 500us for clock stretch to complete during unstick
+#define UNSTICK_CLK_STRETCH (500 / UNSTICK_CLK_US)
+
+// wait for SCL to return high (clock stretching)
+static bool i2cUnstick_waitStretch(IO_t scl, int timeout)
+{
+    bool sclVal;
+    while (!(sclVal = IORead(scl)) && timeout) {
+        delayMicroseconds(UNSTICK_CLK_US);
+        timeout--;
+    }
+    return sclVal;
+}
+
+// generate clock pulses + STOP on I2C bus
+// this should get all devices into idle state
+// return true if bus seems to be idle (both SCL and SDA are high)
+bool i2cUnstick(IO_t scl, IO_t sda)
+{
+    // output value first to prevent glitch after switching direction
+    IOHi(scl);
+    IOHi(sda);
+
+    // bus was probably in I2C (alternate function) mode
+    IOConfigGPIO(scl, IOCFG_OUT_OD);
+    IOConfigGPIO(sda, IOCFG_OUT_OD);
+
+    // Clock out, with SDA high:
+    // 7 data bits, 1 READ bit, 1 cycle for the ACK
+    for (int i = 0; i < (7 + 1 + 1); i++) {
+        // Wait for any clock stretching to finish
+        i2cUnstick_waitStretch(scl, UNSTICK_CLK_STRETCH);
+        // Pull low
+        IOLo(scl); // Set bus low
+        delayMicroseconds(UNSTICK_CLK_US / 2);
+        IOHi(scl); // Set bus high
+        delayMicroseconds(UNSTICK_CLK_US / 2);
+    }
+    // slave may be still stretching after last pulse
+    i2cUnstick_waitStretch(scl, UNSTICK_CLK_STRETCH);
+
+    // Generate a stop condition in case there was none
+    // SCL low pulse to switch SDA low
+    IOLo(scl);
+    delayMicroseconds(UNSTICK_CLK_US / 2);
+    IOLo(sda);
+    delayMicroseconds(UNSTICK_CLK_US / 2);
+    IOHi(scl);
+    delayMicroseconds(UNSTICK_CLK_US / 2);
+     // SDA rising edge = STOP
+    IOHi(sda);
+    // check that both SCL and SDA are high
+    delayMicroseconds(UNSTICK_CLK_US / 2);  // time for SDA to return high
+    bool ok = IORead(scl) && IORead(sda);
+    // I2C ping are left in GPIO mode
+    return ok;
+}

src/main/drivers/bus_i2c_utils.h

@@ -0,0 +1,28 @@
+/*
+ * This file is part of Betaflight.
+ *
+ * Betaflight is free software. You can redistribute this software
+ * and/or modify this software under the terms of the GNU General
+ * Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * Betaflight is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this software.
+ *
+ * If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+/*
+ * common functions shared by different I2C implementations
+ */
+
+bool i2cUnstick(IO_t scl, IO_t sda);

src/main/drivers/stm32/bus_i2c_hal_init.c

@@ -27,7 +27,6 @@
 #if defined(USE_I2C) && !defined(SOFT_I2C)
 
 #include "drivers/io.h"
-#include "drivers/io_impl.h"
 #include "drivers/nvic.h"
 #include "drivers/time.h"
 #include "drivers/rcc.h"
@@ -35,19 +34,7 @@
 #include "drivers/bus_i2c.h"
 #include "drivers/bus_i2c_impl.h"
 #include "drivers/bus_i2c_timing.h"
-
+#include "drivers/bus_i2c_utils.h"
-// Number of bits in I2C protocol phase
-#define LEN_ADDR 7
-#define LEN_RW 1
-#define LEN_ACK 1
-
-// Clock period in us during unstick transfer
-#define UNSTICK_CLK_US 10
-
-// Allow 500us for clock strech to complete during unstick
-#define UNSTICK_CLK_STRETCH (500/UNSTICK_CLK_US)
-
-static void i2cUnstick(IO_t scl, IO_t sda);
 
 #define IOCFG_I2C_PU IO_CONFIG(GPIO_MODE_AF_OD, GPIO_SPEED_FREQ_VERY_HIGH, GPIO_PULLUP)
 #define IOCFG_I2C    IO_CONFIG(GPIO_MODE_AF_OD, GPIO_SPEED_FREQ_VERY_HIGH, GPIO_NOPULL)
@@ -287,44 +274,4 @@ void i2cInit(I2CDevice device)
     HAL_NVIC_EnableIRQ(hardware->ev_irq);
 }
 
-static void i2cUnstick(IO_t scl, IO_t sda)
-{
-    int i;
-
-    IOHi(scl);
-    IOHi(sda);
-
-    IOConfigGPIO(scl, IOCFG_OUT_OD);
-    IOConfigGPIO(sda, IOCFG_OUT_OD);
-
-    // Clock out, with SDA high:
-    //   7 data bits
-    //   1 READ bit
-    //   1 cycle for the ACK
-    for (i = 0; i < (LEN_ADDR + LEN_RW + LEN_ACK); i++) {
-        // Wait for any clock stretching to finish
-        int timeout = UNSTICK_CLK_STRETCH;
-        while (!IORead(scl) && timeout) {
-            delayMicroseconds(UNSTICK_CLK_US);
-            timeout--;
-        }
-
-        // Pull low
-        IOLo(scl); // Set bus low
-        delayMicroseconds(UNSTICK_CLK_US/2);
-        IOHi(scl); // Set bus high
-        delayMicroseconds(UNSTICK_CLK_US/2);
-    }
-
-    // Generate a stop condition in case there was none
-    IOLo(scl);
-    delayMicroseconds(UNSTICK_CLK_US/2);
-    IOLo(sda);
-    delayMicroseconds(UNSTICK_CLK_US/2);
-
-    IOHi(scl); // Set bus scl high
-    delayMicroseconds(UNSTICK_CLK_US/2);
-    IOHi(sda); // Set bus sda high
-}
-
 #endif

src/main/drivers/stm32/bus_i2c_stm32f4xx.c

@@ -34,21 +34,10 @@
 
 #include "drivers/bus_i2c.h"
 #include "drivers/bus_i2c_impl.h"
-
+#include "drivers/bus_i2c_utils.h"
-// Number of bits in I2C protocol phase
-#define LEN_ADDR 7
-#define LEN_RW 1
-#define LEN_ACK 1
-
-// Clock period in us during unstick transfer
-#define UNSTICK_CLK_US 10
-
-// Allow 500us for clock strech to complete during unstick
-#define UNSTICK_CLK_STRETCH (500/UNSTICK_CLK_US)
 
 static void i2c_er_handler(I2CDevice device);
 static void i2c_ev_handler(I2CDevice device);
-static void i2cUnstick(IO_t scl, IO_t sda);
 
 #ifdef STM32F4
 #define IOCFG_I2C_PU IO_CONFIG(GPIO_Mode_AF, 0, GPIO_OType_OD, GPIO_PuPd_UP)
@@ -513,44 +502,4 @@ uint16_t i2cGetErrorCounter(void)
     return i2cErrorCount;
 }
 
-static void i2cUnstick(IO_t scl, IO_t sda)
-{
-    int i;
-
-    IOHi(scl);
-    IOHi(sda);
-
-    IOConfigGPIO(scl, IOCFG_OUT_OD);
-    IOConfigGPIO(sda, IOCFG_OUT_OD);
-
-    // Clock out, with SDA high:
-    //   7 data bits
-    //   1 READ bit
-    //   1 cycle for the ACK
-    for (i = 0; i < (LEN_ADDR + LEN_RW + LEN_ACK); i++) {
-        // Wait for any clock stretching to finish
-        int timeout = UNSTICK_CLK_STRETCH;
-        while (!IORead(scl) && timeout) {
-            delayMicroseconds(UNSTICK_CLK_US);
-            timeout--;
-        }
-
-        // Pull low
-        IOLo(scl); // Set bus low
-        delayMicroseconds(UNSTICK_CLK_US/2);
-        IOHi(scl); // Set bus high
-        delayMicroseconds(UNSTICK_CLK_US/2);
-    }
-
-    // Generate a stop condition in case there was none
-    IOLo(scl);
-    delayMicroseconds(UNSTICK_CLK_US/2);
-    IOLo(sda);
-    delayMicroseconds(UNSTICK_CLK_US/2);
-
-    IOHi(scl); // Set bus scl high
-    delayMicroseconds(UNSTICK_CLK_US/2);
-    IOHi(sda); // Set bus sda high
-}
-
 #endif