drivers/soft_i2c: Add bit-banging I2C using GPIO LL #20333
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Platform: ARM
This implements `i2c_pin_sda()` and `i2c_pin_scl()` as regular C functions instead of preprocessor macros.
This implements a bit-banged I2C bus using GPIO LL either using the `periph_gpio_ll_open_drain` feature or ,as fall-back, using the `periph_gpio_ll_switch_dir` feature. The implementation should work with clock-stretching and arbitration. It should also be able to detect a locked bus and recover from it.
With the new feature it should be possible to just use a software I2C bus instead of a `periph_i2c` using the same APIs. I tested this using the following patch using an SHT3X breakout board connected to an nRF52840-DK: ```diff --- a/tests/drivers/sht3x/Makefile +++ b/tests/drivers/sht3x/Makefile @@ -2,4 +2,19 @@ include ../Makefile.drivers_common USEMODULE += sht3x +PIN_SCL ?= GPIO_PIN(0,27) +PIN_SDA ?= GPIO_PIN(0,26) + +ifneq (,$(PIN_SCL)) + CFLAGS += "-DSOFT_I2C_PARAM_SCL=$(PIN_SCL)" +endif +ifneq (,$(PIN_SDA)) + CFLAGS += "-DSOFT_I2C_PARAM_SDA=$(PIN_SDA)" +endif + +USEMODULE += soft_i2c +USEMODULE += soft_i2c_as_periph_i2c + +CFLAGS += "-DSHT3X_PARAM_I2C_ADDR=SHT3X_I2C_ADDR_1" + include $(RIOTBASE)/Makefile.include ```
Just passing the flag `SOFT_I2C=` while building will use the software I2C bus instead of the hardware I2C bus.
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Contribution description
This implements a bit-banged I2C bus using GPIO LL either using the
periph_gpio_ll_open_drainfeature or ,as fall-back, using theperiph_gpio_ll_switch_dirfeature.The implementation should work with clock-stretching and arbitration. It should also be able to detect a locked bus and recover from it.
A pseudomodule
soft_i2c_as_periph_i2cis added to allow thesoft_i2cproviding theperiph_i2cAPI.Testing procedure
I tested this using the following patch using an SHT3X breakout board connected to an nRF52840-DK:
Capture with a Logic Analyzer
Console output
Beware: This has not been tested on boards that have no open drain GPIOs but implement
periph_gpio_ll_switch_dir. I'll add that in time.Issues/PRs references
Depends on and includes: