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Fix I2C recovery on Arduino (#2412)
Co-authored-by: Maurice Makaay <mmakaay1@xs4all.net>
This commit is contained in:
Maurice Makaay
GitHub
parent
5a2984d03a
commit
d0dfc94a61
2 changed files with 117 additions and 20 deletions
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@ -32,6 +32,17 @@ void ArduinoI2CBus::dump_config() {
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ESP_LOGCONFIG(TAG, " SDA Pin: GPIO%u", this->sda_pin_);
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ESP_LOGCONFIG(TAG, " SCL Pin: GPIO%u", this->scl_pin_);
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ESP_LOGCONFIG(TAG, " Frequency: %u Hz", this->frequency_);
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switch (this->recovery_result_) {
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case RECOVERY_COMPLETED:
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ESP_LOGCONFIG(TAG, " Recovery: bus successfully recovered");
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break;
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case RECOVERY_FAILED_SCL_LOW:
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ESP_LOGCONFIG(TAG, " Recovery: failed, SCL is held low on the bus");
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break;
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case RECOVERY_FAILED_SDA_LOW:
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ESP_LOGCONFIG(TAG, " Recovery: failed, SDA is held low on the bus");
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break;
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}
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if (this->scan_) {
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ESP_LOGI(TAG, "Scanning i2c bus for active devices...");
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uint8_t found = 0;
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@ -92,31 +103,110 @@ ErrorCode ArduinoI2CBus::writev(uint8_t address, WriteBuffer *buffers, size_t cn
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return ERROR_UNKNOWN;
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}
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/// Perform I2C bus recovery, see:
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/// https://www.nxp.com/docs/en/user-guide/UM10204.pdf
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/// https://www.analog.com/media/en/technical-documentation/application-notes/54305147357414AN686_0.pdf
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void ArduinoI2CBus::recover_() {
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// Perform I2C bus recovery, see
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// https://www.analog.com/media/en/technical-documentation/application-notes/54305147357414AN686_0.pdf
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// or see the linux kernel implementation, e.g.
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// https://elixir.bootlin.com/linux/v5.14.6/source/drivers/i2c/i2c-core-base.c#L200
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ESP_LOGI(TAG, "Performing I2C bus recovery");
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// try to get about 100kHz toggle frequency
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const auto half_period_usec = 1000000 / 100000 / 2;
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const auto recover_scl_periods = 9;
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// configure scl as output
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pinMode(scl_pin_, OUTPUT); // NOLINT
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// set scl high
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digitalWrite(scl_pin_, 1); // NOLINT
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// in total generate 9 falling-rising edges
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for (auto i = 0; i < recover_scl_periods; i++) {
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delayMicroseconds(half_period_usec);
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digitalWrite(scl_pin_, 0); // NOLINT
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delayMicroseconds(half_period_usec);
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digitalWrite(scl_pin_, 1); // NOLINT
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// Activate the pull up resistor on the SCL pin. This should make the
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// signal on the line HIGH. If SCL is pulled low on the I2C bus however,
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// then some device is interfering with the SCL line. In that case,
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// the I2C bus cannot be recovered.
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pinMode(scl_pin_, INPUT_PULLUP); // NOLINT
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if (digitalRead(scl_pin_) == LOW) { // NOLINT
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ESP_LOGE(TAG, "Recovery failed: SCL is held LOW on the I2C bus");
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recovery_result_ = RECOVERY_FAILED_SCL_LOW;
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return;
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}
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// From the specification:
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// "If the data line (SDA) is stuck LOW, send nine clock pulses. The
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// device that held the bus LOW should release it sometime within
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// those nine clocks."
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// We don't really have to detect if SDA is stuck low. We'll simply send
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// nine clock pulses here, just in case SDA is stuck.
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// Use a 100kHz toggle frequency (i.e. the maximum frequency for I2C
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// running in standard-mode). The resulting frequency will be lower,
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// because of the additional function calls that are done, but that
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// is no problem.
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const auto half_period_usec = 1000000 / 100000 / 2;
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// Make sure that switching to mode OUTPUT will make SCL low, just in
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// case other code has setup the pin to output a HIGH signal.
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digitalWrite(scl_pin_, LOW); // NOLINT
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// Activate the pull up resistor for SDA, so after the clock pulse cycle
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// we can verify if SDA is pulled high. Also make sure that switching to
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// mode OUTPUT will make SDA low.
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pinMode(sda_pin_, INPUT_PULLUP); // NOLINT
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digitalWrite(sda_pin_, LOW); // NOLINT
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ESP_LOGI(TAG, "Sending 9 clock pulses to drain any stuck device output");
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delayMicroseconds(half_period_usec);
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for (auto i = 0; i < 9; i++) {
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// Release pull up resistor and switch to output to make the signal LOW.
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pinMode(scl_pin_, INPUT); // NOLINT
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pinMode(scl_pin_, OUTPUT); // NOLINT
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delayMicroseconds(half_period_usec);
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// Release output and activate pull up resistor to make the signal HIGH.
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pinMode(scl_pin_, INPUT); // NOLINT
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pinMode(scl_pin_, INPUT_PULLUP); // NOLINT
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delayMicroseconds(half_period_usec);
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// When SCL is kept LOW at this point, we might be looking at a device
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// that applies clock stretching. Wait for the release of the SCL line,
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// but not forever. There is no specification for the maximum allowed
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// time. We'll stick to 500ms here.
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auto wait = 20;
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while (wait-- && digitalRead(scl_pin_) == LOW) { // NOLINT
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delay(25);
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}
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if (digitalRead(scl_pin_) == LOW) { // NOLINT
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ESP_LOGE(TAG, "Recovery failed: SCL is held LOW during clock pulse cycle");
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recovery_result_ = RECOVERY_FAILED_SCL_LOW;
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return;
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}
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}
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// By now, any stuck device ought to have sent all remaining bits of its
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// transation, meaning that it should have freed up the SDA line, resulting
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// in SDA being pulled up.
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if (digitalRead(sda_pin_) == LOW) { // NOLINT
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ESP_LOGE(TAG, "Recovery failed: SDA is held LOW after clock pulse cycle");
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recovery_result_ = RECOVERY_FAILED_SDA_LOW;
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return;
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}
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// From the specification:
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// "I2C-bus compatible devices must reset their bus logic on receipt of
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// a START or repeated START condition such that they all anticipate
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// the sending of a target address, even if these START conditions are
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// not positioned according to the proper format."
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// While the 9 clock pulses from above might have drained all bits of a
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// single byte within a transaction, a device might have more bytes to
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// transmit. So here we'll generate a START condition to snap the device
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// out of this state.
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// SCL and SDA are already high at this point, so we can generate a START
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// condition by making the SDA signal LOW.
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ESP_LOGI(TAG, "Generate START condition to reset bus logic of I2C devices");
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pinMode(sda_pin_, INPUT); // NOLINT
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pinMode(sda_pin_, OUTPUT); // NOLINT
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delayMicroseconds(half_period_usec);
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// From the specification:
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// "A START condition immediately followed by a STOP condition (void
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// message) is an illegal format. Many devices however are designed to
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// operate properly under this condition."
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// Finally, we'll bring the I2C bus into a starting state by generating
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// a STOP condition.
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ESP_LOGI(TAG, "Generate STOP condition to finalize recovery");
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pinMode(sda_pin_, INPUT); // NOLINT
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pinMode(sda_pin_, INPUT_PULLUP); // NOLINT
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recovery_result_ = RECOVERY_COMPLETED;
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}
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} // namespace i2c
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} // namespace esphome
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@ -9,6 +9,12 @@
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namespace esphome {
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namespace i2c {
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enum RecoveryCode {
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RECOVERY_FAILED_SCL_LOW,
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RECOVERY_FAILED_SDA_LOW,
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RECOVERY_COMPLETED,
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};
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class ArduinoI2CBus : public I2CBus, public Component {
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public:
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void setup() override;
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@ -24,6 +30,7 @@ class ArduinoI2CBus : public I2CBus, public Component {
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private:
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void recover_();
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RecoveryCode recovery_result_;
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protected:
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TwoWire *wire_;
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