Help a noob debug via USB UART serial a Nanopi

[TheLinuxGuy]

I am troubleshooting a Nanopi R4S that seems to be unable to boot after being configured in OpenWRT. This is my first headless and my first single board computer, so bare with me my noob questions.

I can't seem to be able to get a serial console working to output normal readable text. Most my text is like this:

These are the resources I have been using:

• https://wiki.friendlyarm.com/wiki/index.php/NanoPi_R4S
• https://wiki.t-firefly.com/en/ROC-RK3399-PC/debug.html
• https://sparks.gogo.co.nz/ch340.html (windows driver for CH340 rs232 ttl)

My windows driver seems to be properly installed.

I am assuming that my USB UART device RX and TX cables must be matched. Meaning:

• R4S UART4-RX to TTL-RXD
• R4S UART4-TX to TTL-TXD
• R4S UART4-GND to TTL-GND

What could I possibly be doing wrong? I'm out of ideas, tried swapping cables playing with lowering baud rates in putty.exe - nothing...

[anon50098793]

@TheLinuxGuy

• R4S UART4-RX to TTL-RXD
• R4S UART4-TX to TTL-TXD

have not read the wiki but typically

TX > RX
RX < TX

[TheLinuxGuy]

@anon50098793

have not read the wiki but typically

TX > RX
RX < TX

This helps! I wasn't sure. I reversed the polarity between the two.

I took a second look at the wiki - I have always been using the following connections

• "GPIO1_B0/SPI1_TXD/UART4-TX"
• "GPIO1_A7/SPI1_RXD/UART4-RX"

Apparently those are completely different than serial? I totally missed the "3 pin UART" hidden behind the usb c charger side of the board here:

Then implementing your suggestion of reverse polarity voila it worked. Thanks a lot ... so is "GPIO" a different kind of protocol non-serial then?