Using GPIO4 and GPIO3

In my project, I would like to use pins GPIO4 and GPIO3 (on the wolfson card) to attach and control 2 leds. I would like to use these to give some feedback to the user about my program while no screen is attached.

Is this possible? If so, how to swtich on/off these pins? Can I use the stock RPI.GPIO python module using the following code:

GPIO.output(15, True) #for gpio3

GPIO.output(16, True) #for gpio4

Best

Dieter

0 Former Member over 11 years ago

Your best option for just 2 LEDs is to use GPIO14/15, the UART lines.
Disable the serial boot logging and the default serial console and you can use these two lines as general I/O pins.

Edit boot commandline:
sudo nano /boot/cmdline.txt
Remove "console=ttyAMA0,115200 kgdboc=ttyAMA0,115200"

Edit /etc/inittab:
sudo nano etc/inttab
Comment the line "2:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100"
by adding a hash '#' at the start of the line.

Reboot and GPIO14 & GPIO15 (BCM nmubering) are available as I/O lines.

Tutorial here

I connected a pair of LEDs to the J8 header on my Wolfson card yesterday.
Cancel
Vote Up 0 Vote Down

Sign in to reply

Verify Answer

Cancel
0 Former Member over 11 years ago in reply to Former Member

Thanks for this.

Does this mean that gpio3 and gpio4 are not simpely passed through from the Pi? Are they connected to the chipset of the wolfson card?
Cancel
Vote Up 0 Vote Down

Sign in to reply

Verify Answer

Cancel
0 Former Member over 11 years ago in reply to Former Member

I don't think GPIO3 & GPIO4 on the Expand Header are RasPi GPIO lines IDs.
WAC.GPIO3 is shown connected to Pi P1.22 (Pi.GPIO25)
WAC.GPIO4 does not seem to connect to the Pi GPIO.
Both are presumably used by the board and not available to you for general IO.

See the schematic
Cancel
Vote Up 0 Vote Down

Sign in to reply

Verify Answer

Cancel