A linux kernel module for the tpic6c595 shift-register. The tpic6c595 is a 8-bit shift register by Texas Instruments. It's typically used for power driver applications including relays, solenoids, and other low-current or medium-voltage loads.
The tpic6c595 can be chained with other registers of the same type, thus providing any multiple of eight outputs. This way it can be used to provide a plethora of output pins by using only four GPIOs.
By using this kernel driver the shift-register can be directly accessed through a character-device located at /dev/tpic6c595. The driver can be configured through ioctl() and supports the write()-call to set it's pins by writing bitmasks to it.
This project was created to demonstrate the development of a linux-module. For demonstration purpose, an interrupt-handler is registered to be fired when the user hits a hardware-button. The function of the button can be configured and is demonstrated in the example-section.
tpic6c595_test.c contains an example program that uses the driver to control the shift-register from userspace. A prototype PCB was soldered to show the functionality the of the driver. It uses two tpic6c595 shift-registers to supply a total of 16 outputs. These outputs can be accessed through pin-headers on the PCB and their status is indicated by LEDs.
The button is configured to give a knight-rider like effect:
The button is configured to flash the outputs, doesn't look right on the gif because of the low frame-rate:
Ascending values from 0x0000 to 0xffff are written to the device:
During development a test-setup was used and the correctness of the signals was observed using an oscilloscope.
