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machine/esp32xx: clear the I2C bus with a GPIO STOP when configuring #5783

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Merged
deadprogram merged 1 commit into from
Sep 29, 2026
+31 −2
Merged

machine/esp32xx: clear the I2C bus with a GPIO STOP when configuring #5783

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33 changes: 31 additions & 2 deletions src/machine/machine_esp32xx_i2c.go
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {

i2c.initClock(config)
i2c.initNoiseFilter()
i2c.clearBus(config)
i2c.initPins(config)
i2c.initFrequency(config)
i2c.startMaster()
Expand Down Expand Up @@ -72,6 +73,36 @@ func (i2c *I2C) initNoiseFilter() {
i2c.Bus.FILTER_CFG.Set(0x377)
}

// clearBus clocks SCL until SDA is released and then sends a STOP, both as GPIOs.
// Same as ESP-IDF https://github.com/espressif/esp-idf/blob/v4.4.8/components/driver/i2c.c#L579
func (i2c *I2C) clearBus(config I2CConfig) {
const halfPeriodNS = 5000
wait := func() {
end := nanotime() + halfPeriodNS
for nanotime() < end {
}
}
scl, sda := config.SCL, config.SDA
scl.Configure(PinConfig{Mode: PinOutput})
scl.pinReg().SetBits(esp.GPIO_PIN_PAD_DRIVER)
sda.Configure(PinConfig{Mode: PinOutput})
sda.pinReg().SetBits(esp.GPIO_PIN_PAD_DRIVER)
scl.Low()
sda.High()
wait()
for i := 0; i < 9 && !sda.Get(); i++ {
scl.High()
wait()
scl.Low()
wait()
}
sda.Low()
scl.High()
wait()
sda.High()
wait()
}

//go:inline
func (i2c *I2C) initPins(config I2CConfig) {
config.SDA.configure(PinConfig{Mode: PinOutput}, i2c.funcSDA)
Expand Down Expand Up @@ -139,8 +170,6 @@ func (i2c *I2C) startMaster() {
func (i2c *I2C) resetMaster() {
// reset FSM
i2c.Bus.SetCTR_FSM_RST(1)
// No bus clear (SCL_RST_SLV), a GT911 did not ACK the next transaction after it.
// ESP-IDF does not clear the bus on init either https://github.com/espressif/esp-idf/blob/v4.4.8/components/driver/i2c.c#L673
i2c.Bus.SetSCL_STRETCH_CONF_SLAVE_SCL_STRETCH_EN(1)
i2c.Bus.SetCTR_CONF_UPGATE(1)
i2c.Bus.FILTER_CFG.Set(0x377)
Expand Down
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