LED on Serial TX

Mr. Waffles

I hooked an LED to the TX and Ground pins and enabled serial connections in the settings, but I am unable to get the LED to light up. When I first enabled Serial from the raspi-config menu the LED state would change when the pi was turned on or off, but after installing DOSBox the LED only lights up for a brief second during system startup or a system reboot.

Any ideas on how I can get this thing working again? Is there another boot config file that is overwriting the /boot/config.txt file?

I am using Raspberry Pi 3 and Retropie 4.2.

Mr. Waffles

Any help would be greatly appreciated.

Mr. Waffles

After digging around a while, I have determined that the serial pin is indeed enabled and is being turned of by an unknown startup script.

Mr. Waffles

While I still have no idea what caused the issue (and welcome responses from anyone who does), the following is a long-term fix for anyone with a similar problems. This should work for fans and other components using ANY of the GPIO pins.

Install http://wiringpi.com/the-gpio-utility/

Open a terminal and type sudo nano /etc/rc.local

Enter the following immediately after the #!/bin/sh -e:

/usr/local/bin/gpio -g mode 14 out
/usr/local/bin/gpio -g write 14 1

Make sure the document contains exit 0 at the end of it.
Note: 14 is the GPIO number and NOT the pin number. This number can be switched to other GPIO.

Crtl+x to exit
y to save
Enter to overwrite the previous file
Reboot and the pin should switch to on.

Note: Due my particular issue, this solution causes my led/fan/component to flicker once during boot.

edmaul69

@Mr.-Waffles just out of curiousity, which adapter and what you are using the serial pins for? I am always looking for more reasons to add more stuff to my pi

Mr. Waffles

I placed my pi in an old SNES case. I wanted to get it as close to a real SNES as possible, so I've wired the original power and reset switches to the GPIO along with a small fan and thermostat which I've set to kick on if things get too hot. With the solution in this post I've also wired an LED to the GPIO. I currently have the LED hooked to the TX pin, but that was because it was supposed to kick on and off without any extra code. Since I had to use the solution in this post I suppose I may free up the serial port for some future enhancements.

Currently I am using CanaKit 5V 2.5a power supply which you can pick up for fairly cheap on Amazon. You would be hard pressed to push the pi beyond 2.5a.