Troubleshooting

When I started this project, I'd never worked with RPi gpio. I think I got just about everything backwards possible. I blew up a MAX-31855 chip... POOF, up in smoke!

So, invest a little time to learn the hardware and the software available to you to veriy everything works as expected.

Breadboard Orientation

If you're using a breadboard with a labeled break-out board, verify:

where pin one is using a multimeter. it sounds stupid, but it will save you time.
measure the voltage between all the 3V3 pins and a GND pin
measure the voltage betwwen all the GND pins and a GND pin
measure the voltage between the 5V pins and a GND pin.

Test Each GPIO Pin

At thought I one point that I had fried my RPi. I needed to verify that it still worked as expected. Here's what I did to verify GPIO on my pi.

'''gpio readall'''

''' +-----+-----+---------+------+---+---Pi 3---+---+------+---------+-----+-----+ | BCM | wPi | Name | Mode | V | Physical | V | Mode | Name | wPi | BCM | +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+ | | | 3.3v | | | 1 || 2 | | | 5v | | | | 2 | 8 | SDA.1 | IN | 1 | 3 || 4 | | | 5v | | | | 3 | 9 | SCL.1 | IN | 1 | 5 || 6 | | | 0v | | | | 4 | 7 | GPIO. 7 | IN | 0 | 7 || 8 | 0 | IN | TxD | 15 | 14 | | | | 0v | | | 9 || 10 | 1 | IN | RxD | 16 | 15 | | 17 | 0 | GPIO. 0 | IN | 0 | 11 || 12 | 1 | IN | GPIO. 1 | 1 | 18 | | 27 | 2 | GPIO. 2 | IN | 0 | 13 || 14 | | | 0v | | | | 22 | 3 | GPIO. 3 | IN | 0 | 15 || 16 | 0 | IN | GPIO. 4 | 4 | 23 | | | | 3.3v | | | 17 || 18 | 0 | IN | GPIO. 5 | 5 | 24 | | 10 | 12 | MOSI | IN | 0 | 19 || 20 | | | 0v | | | | 9 | 13 | MISO | IN | 0 | 21 || 22 | 0 | IN | GPIO. 6 | 6 | 25 | | 11 | 14 | SCLK | IN | 0 | 23 || 24 | 1 | IN | CE0 | 10 | 8 | | | | 0v | | | 25 || 26 | 1 | IN | CE1 | 11 | 7 | | 0 | 30 | SDA.0 | IN | 0 | 27 || 28 | 1 | IN | SCL.0 | 31 | 1 | | 5 | 21 | GPIO.21 | IN | 0 | 29 || 30 | | | 0v | | | | 6 | 22 | GPIO.22 | IN | 0 | 31 || 32 | 0 | IN | GPIO.26 | 26 | 12 | | 13 | 23 | GPIO.23 | IN | 0 | 33 || 34 | | | 0v | | | | 19 | 24 | GPIO.24 | IN | 0 | 35 || 36 | 0 | IN | GPIO.27 | 27 | 16 | | 26 | 25 | GPIO.25 | IN | 0 | 37 || 38 | 0 | IN | GPIO.28 | 28 | 20 | | | | 0v | | | 39 || 40 | 0 | IN | GPIO.29 | 29 | 21 | +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+ | BCM | wPi | Name | Mode | V | Physical | V | Mode | Name | wPi | BCM | +-----+-----+---------+------+---+---Pi 3---+---+------+---------+-----+-----+ '''

make sure the mode for all GPIO pins you want to test have a Mode of IN if not, set the mode for each..

set BCM pin 4 as an input

gpio -g mode 4 input

verify it got set correctly using

gpio readall

enable pull-down resistor for pin 4 to make sure V stays

zero when nothing is connected to the input

gpio -g mode 4 down

watch gpio readall

connect a 3V3 pin in series to a 1k ohm resistor connect the other end of the resistor to each gpio pin when it is connected V should be 1 when it is disconnected V should be 0 my breadboard uses the BCM gpio pin numbering

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