Hi v8dave, sorry for not replying I've been busy on other project. Today I had a chance to retest everything. As for your question, yes I did not connect 5V it was only RX,TX and GND. Conclusion is: not compatible USB-C power supply I have connected to USB-C psu of my laptop and it was same stuff (r...

yes it is 3.3V USB to TTL cable from Adafruit. Specs are here:

https://www.adafruit.com/product/954

v8dave wrote:
Gibberish usually indicates a missing ground connection.

it happens with or without ground

UPDATE!!!

ok now I am completely baffled. After finishing the boot on serial with gibberish, I have connected HDMI cable and I get the image. Just for information I have serial 2 USB cable from Adafruit with CP2102. I am going to test second board.

Thanks that is exactly what I did. Without HDMI cable connected I am getting gibberish output on serial as shown on attached image. My serial settings are (same settings work fine with for example nanopi core2): speed: 115200 Data bits: 8 Stop bits: 1 Parity: None XON/XOFF Funnily board seems to be ...

Hello guys, I have two NEO 4 boards with heatsinks. Unfortunately both of them are stuck in boot cycle. When I connect power, they briefly show FriendlyElec logo on screen and then again and again. I am using sd card with rk3399-sd-friendlycore-bionic-4.4-arm64-20191227.img image. Via console on usb...