a6b459eff3
It turns out that the feature to switch the GPIO direction quickly is not only a way to emulate open drain / open source mode for less sophisticated GPIO peripherals that do not natively support it. It also enables tri-state output (push-pull high, push-pull low, high impedance), which is useful e.g. for driven charlieplexed LEDs quickly. This changes the API by introducing a `gpio_ll_prepare_switch_dir()` function that prepares the value used to identify which pins should be switched to input or to output mode. This is useful for GPIO peripherals in which the GPIO mode register does not allocate one bit per pin (so that only the direction is given there), such as the one for STM32. This allows an STM32 implementation in which preparing the bitmask needed to modify the direction of pins is not trivial.
Test for periph/gpio_ll
This application will use two output and two input GPIOs, which have to be connected via a jumper wire. The test will change the value of the two pins output pins and use the input pins to read the value back in. If the value read doesn't match the expected result, the test aborts and fails.
If IRQ support is provided, the test will additionally walk through every IRQ configuration for the first GPIO pin given and iterate over any trigger condition possible. It will check that edge trigger and (if supported) level trigger IRQs trigger exactly on the configured triggers.
Configuration
Configure in the Makefile or set via environment variables the number of
the output GPIO port to use via the PORT_OUT variable. The PIN_OUT_0 and
PIN_OUT_1 variables select the pins to use within that GPIO port. The input
GPIO port is set via PORT_IN. Both PORT_IN == PORT_OUT and
PORT_IN != PORT_OUT is valid. The input pin number within PORT_IN are set
via PIN_IN_0 and PIN_IN_1. PIN_IN_0 has to be wired to PIN_OUT_0, and
PIN_IN_1 to PIN_OUT_1.
Expected Failures
Implementations are allowed to not electrically disconnect GPIO pins in state
GPIO_DISCONNECT. The test will however test for pins to be electrically
disconnected. For every MCU supported by GPIO LL so far at least some pins can
be electrically disconnected. You might need to change the GPIO pins tested
if the test for disconnected GPIOs being also electrically disconnected.
When features such as periph_gpio_ll_pull_up or periph_gpio_ll_open_drain
are provided, this test expect those to be available on the tested pins. If
those features are not available on all pins, suitable pins need to be
selected for the test to pass.