But I'd need some kind of hardware device to sample the output of the pins, right?
There is no way to just try to write to a pin and see if it can be set from software? Maybe some error message if something goes wrong?
I'm not too hot with designing my own hardware
Set pin 1 to 1
Read pin 1: 1. OK
Set pin 2 to 1
Read pin 2: 0. ERROR
woops, line 2 is broken.
Well the only way to tell if the read/write actually happens in hardware is by sending & sampling signals.
You can use a cheap (<$10 digital voltmeter) to measure the voltage on the pins in response to you setting them to 0/1 ( you can use my write program to send out a very slow pulse by changing the speed to say 1 sec intervals)
You can check the input by putting in alternatively 0 or 3.3 volts (2 1.5 volt batteries in series between ground and the pin will work or use the internal 3.3 (not 5v) signal if it is broken out for you on the sdio connector (or open the plug and go inside to access the 3.3v test pin somewhere).
Or you can just let the pin float if it is not attached to a pull-up/pull-down resistor and you will see the inputs change fast from 0 to 1