RIOT/tests/drivers/pcf857x

Texas Instruments PCF857X I2C I/O expanders test application

Overview

This test application demonstrates the usage of the PCF857X driver interface and can be used to test each PCF857X expander I/O pin with shell commands.

Compilation

To use the test application, compile it with one or more of the pseudomodules pcf8574, pcf8574a or pcf8575 to enable the driver for your expander modules. Please check the default configuration parameters in $(RIOTBASE)/drivers/pcf857x/include/pcf857x_params.h and modify them if necessary. Alternatively, a modified version of this file could be placed in the directory of this test application to override it.

USEMODULE=pcf8575 make -C tests/drivers/pcf857x BOARD=...

Please note: When no pseudomodule is given, pcf8575 is used by default.

To use external interrupts with the expander I/O pins, the PCF857X low-active open-drain interrupt signal has to be enabled. Add module pcf857x_irq for this purpose and define the MCU interrupt pin by parameter PCF857X_PARAM_INT_PIN, e.g.

CFLAGS="-DPCF857X_PARAM_INT_PIN=\(GPIO_PIN\(0,6\)\)" \
USEMODULE="pcf8575 pcf857x_irq" make -C tests/drivers/pcf857x BOARD=...

Please note: Since interrupts are handled in the context of a separate event thread, enabling interrupts requires more RAM.

Usage

The test allows to use commands as known from GPIO test application for PCF857X expanders:

> help
Command              Description
---------------------------------------
init_out             init as output (push-pull mode)
init_in              init as input w/o pull resistor
init_in_pu           init as input with pull-up
init_od              init as output (open-drain without pull resistor)
init_od_pu           init as output (open-drain with pull-up)
init_int             init as external INT w/o pull resistor
enable_int           enable or disable gpio interrupt
read                 read pin status
set                  set pin to HIGH
clear                set pin to LOW
toggle               toggle pin
bench                run a set of predefined benchmarks

The number of the first PCF857X expander port used by the test application is defined by the macro PCF857X_PORT_0, which is 16 by default. This value can be overridden during compilation, e.g.:

CFLAGS="-DPCF857X_PORT_0=8" \
USEMODULE=pcf8575 make -C tests/drivers/pcf857x BOARD=...

Using the port number defined by PCF857X_PORT_0 and the following port numbers, you can apply the command to the PCF857X expander ports. For example, the following command initializes I/O pin 7 of the first PCF857X expander:

init_out 16 7

Commands with port numbers less than PCF857X_PORT_0 refer to GPIO peripheral ports. Thus, both the I/O pins of the PCF857X expanders as well as the GPIO peripheral pins of the MCU can be addressed by all commands.