Le Potato won't boot with hat attached

Start Boot
1

I am attempting to power a Le Potato via the 5V pins on the GPIO header, through a hat which has a 24VDC to 5VDC @ 2A power supply built in.
When I plug up the header to the board and power it, the red and blue lights turn on immediately, but the green light never turns on, and nothing ever appears on the HDMI display. I am seeing 5V and 3.3V on the requisite GPIO pins.

This same hat powers a Raspberry Pi 3B+ with no issues.

Also, I can remove the hat and power the board through the 5V pins with a USB-to-header adapter and it boots fine.

Please note that the hat is a custom design that I made for RPi and I wanted to use it with Libre also.

I feel there must be a gpio pin on this hat that is preventing the boot process but I am not sure which one, as the RPi doesn’t experience this issue.

But, I originally thought the Le Potato gpio pin header is the same as the RPi gpio header.

It’s not shorted because it is not drawing large current, and also the hat has a built-in fuse that trips at too high current draw.

The power supply on this hat is high quality and capable of supplying 5V @ 2A and has no problem powering a RPI 3B+.

Thx for any pointers!

2

OK I figured this out, but it seems to be a documentation/configuration bug:

It’s because I was using GPIO pin 16 as a GPIO input, with a pull-down to 0V.

According to the official pinout document, GPIO pin 16 is “UART_CTS_A”.

Pulling the pin HIGH at boot, even for a brief instant, allows the boot process to continue. The pin does not need to be held high after a pulse to initiate boot.

Is this serial port active during the boot process?

Why would holding this pin low prevent booting?

Thanks

3

Hello,

What OS are you using?

I’ve found many incompatibilities between GPIO projects that work for RPI vs Libre. However, you may need to install the libretech-wiring-tool. It will allow you to change the states of the GPIO. Remember, you cannot change the states the same as you can for RPI on a Libre board.

4

Are you sure it’s pin 16 and not pin 15? Pin 15 is TEST_N which is the reset pin if the pinmux is set to input and will prevent the board from starting.