3.2 KiB
I sucked at handling my Rpi gpio pins. I got everything backward you could. I blew up a MAX-31855 chip. POOF, UP IN SMOKE! Don't be like me...
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. if everything measures as expected, continue. if not, go back to the first step.
run gpio readall and 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
+-----+-----+---------+------+---+---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---+---+------+---------+-----+-----+
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