3.9 KiB
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 verify 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 between all the GND pins and a GND pin
- measure the voltage between the 5V pins and a GND pin
Test Each GPIO Pin
I thought at 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
and you'll get output that looks something like this...
+-----+-----+---------+------+---+---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 all the GPIO pins you want to test have a Mode of IN to make it in input if not, set the mode for each..
so, for example, to 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
This will show you the output of gpio readall every 2 seconds. This way you can concentrate on moving a wire to each gpio pin and then look up to verify V has changed as you expect without having to type.
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 one at a time
- when it is connected V should be 1
- when it is disconnected V should be 0