From 963b28181fdbcc2c3e77dec5adc7b4c653a6bc7d Mon Sep 17 00:00:00 2001
From: Christian Taedcke <hacking@taedcke.com>
Date: Thu, 23 Sep 2021 20:11:40 +0200
Subject: [PATCH] Always execute i2c bus recovery on setup (#2379)

---
 esphome/components/i2c/i2c_bus_arduino.cpp | 28 ++++++++++++++++
 esphome/components/i2c/i2c_bus_arduino.h   |  3 ++
 esphome/components/i2c/i2c_bus_esp_idf.cpp | 38 ++++++++++++++++++++++
 esphome/components/i2c/i2c_bus_esp_idf.h   |  3 ++
 4 files changed, 72 insertions(+)

diff --git a/esphome/components/i2c/i2c_bus_arduino.cpp b/esphome/components/i2c/i2c_bus_arduino.cpp
index 40d8049617..b983fb7636 100644
--- a/esphome/components/i2c/i2c_bus_arduino.cpp
+++ b/esphome/components/i2c/i2c_bus_arduino.cpp
@@ -2,6 +2,7 @@
 
 #include "i2c_bus_arduino.h"
 #include "esphome/core/log.h"
+#include <Arduino.h>
 #include <cstring>
 
 namespace esphome {
@@ -10,6 +11,7 @@ namespace i2c {
 static const char *const TAG = "i2c.arduino";
 
 void ArduinoI2CBus::setup() {
+  recover();
 #ifdef USE_ESP32
   static uint8_t next_bus_num = 0;
   if (next_bus_num == 0)
@@ -90,6 +92,32 @@ ErrorCode ArduinoI2CBus::writev(uint8_t address, WriteBuffer *buffers, size_t cn
   return ERROR_UNKNOWN;
 }
 
+void ArduinoI2CBus::recover() {
+  // Perform I2C bus recovery, see
+  // https://www.analog.com/media/en/technical-documentation/application-notes/54305147357414AN686_0.pdf
+  // or see the linux kernel implementation, e.g.
+  // https://elixir.bootlin.com/linux/v5.14.6/source/drivers/i2c/i2c-core-base.c#L200
+
+  // try to get about 100kHz toggle frequency
+  const auto half_period_usec = 1000000 / 100000 / 2;
+  const auto recover_scl_periods = 9;
+
+  // configure scl as output
+  pinMode(scl_pin_, OUTPUT);  // NOLINT
+
+  // set scl high
+  digitalWrite(scl_pin_, 1);  // NOLINT
+
+  // in total generate 9 falling-rising edges
+  for (auto i = 0; i < recover_scl_periods; i++) {
+    delayMicroseconds(half_period_usec);
+    digitalWrite(scl_pin_, 0);  // NOLINT
+    delayMicroseconds(half_period_usec);
+    digitalWrite(scl_pin_, 1);  // NOLINT
+  }
+
+  delayMicroseconds(half_period_usec);
+}
 }  // namespace i2c
 }  // namespace esphome
 
diff --git a/esphome/components/i2c/i2c_bus_arduino.h b/esphome/components/i2c/i2c_bus_arduino.h
index 220027b3d4..49be0c358c 100644
--- a/esphome/components/i2c/i2c_bus_arduino.h
+++ b/esphome/components/i2c/i2c_bus_arduino.h
@@ -22,6 +22,9 @@ class ArduinoI2CBus : public I2CBus, public Component {
   void set_scl_pin(uint8_t scl_pin) { scl_pin_ = scl_pin; }
   void set_frequency(uint32_t frequency) { frequency_ = frequency; }
 
+ private:
+  void recover();
+
  protected:
   TwoWire *wire_;
   bool scan_;
diff --git a/esphome/components/i2c/i2c_bus_esp_idf.cpp b/esphome/components/i2c/i2c_bus_esp_idf.cpp
index 8bf97b63ec..5ce5d40c00 100644
--- a/esphome/components/i2c/i2c_bus_esp_idf.cpp
+++ b/esphome/components/i2c/i2c_bus_esp_idf.cpp
@@ -1,6 +1,7 @@
 #ifdef USE_ESP_IDF
 
 #include "i2c_bus_esp_idf.h"
+#include "esphome/core/hal.h"
 #include "esphome/core/log.h"
 #include <cstring>
 
@@ -13,6 +14,8 @@ void IDFI2CBus::setup() {
   static i2c_port_t next_port = 0;
   port_ = next_port++;
 
+  recover();
+
   i2c_config_t conf{};
   memset(&conf, 0, sizeof(conf));
   conf.mode = I2C_MODE_MASTER;
@@ -141,6 +144,41 @@ ErrorCode IDFI2CBus::writev(uint8_t address, WriteBuffer *buffers, size_t cnt) {
   return ERROR_OK;
 }
 
+void IDFI2CBus::recover() {
+  // Perform I2C bus recovery, see
+  // https://www.analog.com/media/en/technical-documentation/application-notes/54305147357414AN686_0.pdf
+  // or see the linux kernel implementation, e.g.
+  // https://elixir.bootlin.com/linux/v5.14.6/source/drivers/i2c/i2c-core-base.c#L200
+
+  // try to get about 100kHz toggle frequency
+  const auto half_period_usec = 1000000 / 100000 / 2;
+  const auto recover_scl_periods = 9;
+  const gpio_num_t scl_pin = static_cast<gpio_num_t>(scl_pin_);
+
+  // configure scl as output
+  gpio_config_t conf{};
+  conf.pin_bit_mask = 1ULL << static_cast<uint32_t>(scl_pin_);
+  conf.mode = GPIO_MODE_OUTPUT;
+  conf.pull_up_en = GPIO_PULLUP_DISABLE;
+  conf.pull_down_en = GPIO_PULLDOWN_DISABLE;
+  conf.intr_type = GPIO_INTR_DISABLE;
+
+  gpio_config(&conf);
+
+  // set scl high
+  gpio_set_level(scl_pin, 1);
+
+  // in total generate 9 falling-rising edges
+  for (auto i = 0; i < recover_scl_periods; i++) {
+    delayMicroseconds(half_period_usec);
+    gpio_set_level(scl_pin, 0);
+    delayMicroseconds(half_period_usec);
+    gpio_set_level(scl_pin, 1);
+  }
+
+  delayMicroseconds(half_period_usec);
+}
+
 }  // namespace i2c
 }  // namespace esphome
 
diff --git a/esphome/components/i2c/i2c_bus_esp_idf.h b/esphome/components/i2c/i2c_bus_esp_idf.h
index c7e67145a3..9985e618f8 100644
--- a/esphome/components/i2c/i2c_bus_esp_idf.h
+++ b/esphome/components/i2c/i2c_bus_esp_idf.h
@@ -24,6 +24,9 @@ class IDFI2CBus : public I2CBus, public Component {
   void set_scl_pullup_enabled(bool scl_pullup_enabled) { scl_pullup_enabled_ = scl_pullup_enabled; }
   void set_frequency(uint32_t frequency) { frequency_ = frequency; }
 
+ private:
+  void recover();
+
  protected:
   i2c_port_t port_;
   bool scan_;