Imported from GitHub: worlickwerx/pi-parport · commit b44e019 · license GPL-2.0

Description

retro parallel port for raspberry pi

README

Testing

These tests primarily check that the bits aren't shorted, open, or misrouted, and the the DTS overlay is properly configured. Ensure that the ppdev module is loaded before running these tests.

loop - plug A

loop A utilizes a DB25 loopback plug wired as below.

Pin	Name	Pin	Name
3	DATA1	14	CONTROL1
4	DATA2	15	STATUS3
5	DATA3	17	CONTROL3
6	DATA4	13	STATUS4
7	DATA5	12	STATUS5
8	DATA6	10	STATUS6
9	DATA7	11	STATUS7

phase 1 DATA is configured for output. Each of 256 possible output values is placed in the DATA register, then the STATUS register is read. The bits from DATA[2,4:7] must appear on STATUS[3:7].

phase 2 DATA is configured for input. Each of 16 possible control values is placed in the CONTROL register, then the DATA register is read. The bits from CONTROL[1,3] must appear on DATA[1,3].

loop - plug B

loop B utilizes a DB25 loopback plug wired as below. It covers the pins missed by plug A.

Pin	Name	Pin	Name
2	DATA0	1	CONTROL0
4	DATA2	16	CONTROL2

DATA is configured for input. Each of 16 possible control values is placed in the CONTROL register, then the DATA register is read. The bits from CONTROL[0,2] must appear on DATA[0,2].

strobe

strobe pin [period] simply toggles a selected pin at a target period so it can be scoped. This is useful for debugging if the loop tests fail.