08-21-2019, 02:27 PM
1) > We get some Uboot messages on boot, after that the port is silent.
There may be a bug.
You should try to another image from the location shown in the following url.
If it works as expected, the problem you pointed out is a kernel bug.
For example,
https://dl.armbian.com/rockpro64/archive/
Armbian_5.67_Rockpro64_Ubuntu_bionic_default_4.4.166.7z
or
https://github.com/ayufan-rock64/linux-b...oad/0.8.3/
bionic-minimal-rockpro64-0.8.3-1141-arm64.img.xz
or etc.
2) > Due to voltage issues, we regulated the TXD and RTX pins to exactly 3.3V (see schematic attached).
Is the product that you pointed out the problem listed below ?
https://store.pine64.org/?product=padi-serial-console
If it is not a defective product and the output signal of a good product is 3.8v, it is a terrible product.
In the presented schematic, you can use resistor splitting to solve the problem,
but if you choose a resistor value that is higher than necessary, the problem arises.
The presence or absence of harmful effects depends on the parasitic capacitance due to the wiring length.
I think it is better to choose a value (220Ω / 1KΩ) that is about 1/100 of the resistance value of the circuit diagram that you presented.
There may be a bug.
You should try to another image from the location shown in the following url.
If it works as expected, the problem you pointed out is a kernel bug.
For example,
https://dl.armbian.com/rockpro64/archive/
Armbian_5.67_Rockpro64_Ubuntu_bionic_default_4.4.166.7z
or
https://github.com/ayufan-rock64/linux-b...oad/0.8.3/
bionic-minimal-rockpro64-0.8.3-1141-arm64.img.xz
or etc.
2) > Due to voltage issues, we regulated the TXD and RTX pins to exactly 3.3V (see schematic attached).
Is the product that you pointed out the problem listed below ?
https://store.pine64.org/?product=padi-serial-console
If it is not a defective product and the output signal of a good product is 3.8v, it is a terrible product.
In the presented schematic, you can use resistor splitting to solve the problem,
but if you choose a resistor value that is higher than necessary, the problem arises.
The presence or absence of harmful effects depends on the parasitic capacitance due to the wiring length.
I think it is better to choose a value (220Ω / 1KΩ) that is about 1/100 of the resistance value of the circuit diagram that you presented.