Serial port cable

[bsammon]

So, I've found threads on the forum that say that the serial port cable being sold by Pine64 is not fully compatible with the Pinebook Pro.
Is that still the case?
Is there somewhere I can buy a compatible serial port cable?
Or do I have to make one myself?

[tllim]

So, I've found threads on the forum that say that the serial port cable being sold by Pine64 is not fully compatible with the Pinebook Pro.
Is that still the case?
Is there somewhere I can buy a compatible serial port cable?
Or do I have to make one myself?

Should works :-)

[z4v4l]

So, I've found threads on the forum that say that the serial port cable being sold by Pine64 is not fully compatible with the Pinebook Pro.
Is that still the case?
Is there somewhere I can buy a compatible serial port cable?
Or do I have to make one myself?

Should works :-)

it has 5V on IO lines! whereas it's supposed to be 3.3V, farthermore, rk3399 uarts want 3.0V (max 3.15)! so it's a two fold problem and indefinitely overlooked. the adapter doesn't work properly and causes instabilities, which is no wonder, given such a voltage mismatch.

[vrabac]

As I would like to debug suspend problem over serial cable, and as I only have the one from pine64 store, it should be really clarified before suggesting that "should works :-)" . If one kills his PBP because of this, will it get replaced free of charge? As coronavirus ban is there, receiving new PBP is almost impossible.

Other than this what is an alternative? To use some kind of jack headphone cable and connect to an USB to TTL Converter with 3.3V? But ifrk3399 uarts want 3.0V (max 3.15) what to do?

[danielt]

So, I've found threads on the forum that say that the serial port cable being sold by Pine64 is not fully compatible with the Pinebook Pro.
Is that still the case?
Is there somewhere I can buy a compatible serial port cable?
Or do I have to make one myself?

Should works :-)

I don't think it does.

For me the excessive voltage level on the adapter TX/PBP RX pin causes the kernel to crash during boot up. My laptop wasn't physically damaged by the over-volting from the adapter but since it doesn't work anyway I saw no reasons to take risks and stopped using it.

I now use a 3.3v TTL adapter from eBay with a hand soldered 3.5mm adapter.

[zaius]

Should works :-)

I don't think it does.

For me the excessive voltage level on the adapter TX/PBP RX pin causes the kernel to crash during boot up. My laptop wasn't physically damaged by the over-volting from the adapter but since it doesn't work anyway I saw no reasons to take risks and stopped using it.

I now use a 3.3v TTL adapter from eBay with a hand soldered 3.5mm adapter.

The crash during boot might be unrelated to the voltage:

"Note: It is not recommended to connect the serial adapter to pin 10 (RX) while booting, as this often causes the board to hang early in the bootloader. Disconnecting pin 10 still allows the serial console to be viewed, and it can be reconnected after the board boots, allowing interaction with the console."

https://nixos.wiki/wiki/NixOS_on_ARM/PIN...al_console

Regardless, Pine should sell a 3.3V adapter, with the correct chipset.   I have no idea why they are selling a 5V adapter when, as far as I know, none of the Pine computers use 5V UART.

[danielt]

The crash during boot might be unrelated to the voltage:

"Note: It is not recommended to connect the serial adapter to pin 10 (RX) while booting, as this often causes the board to hang early in the bootloader. Disconnecting pin 10 still allows the serial console to be viewed, and it can be reconnected after the board boots, allowing interaction with the console."

https://nixos.wiki/wiki/NixOS_on_ARM/PIN...al_console

Regardless, Pine should sell a 3.3V adapter, with the correct chipset.   I have no idea why they are selling a 5V adapter when, as far as I know, none of the Pine computers use 5V UART.

I've seen this note before and I assumed that is was entirely related to the bad voltage (although that doesn't mean that I am right  ).

Basically a TTL serial device "parks" at logic high and will always send out 3.3v or 5v when it is not sending characters. In other words unless you are actively typing then there isn't really anything except for the voltage being applied to the RX pin that could be causing the board to hang.

It is not impossible that there are also crashes when 3.3v is applied to the RX pin but I haven't seen any reports of that on the forum (although now the PBP has become so popular I no longer have time to read all the threads). On the other hand I have seen many reports about problems with the 5v adapter.

[zaius]

Basically a TTL serial device "parks" at logic high and will always send out 3.3v or 5v when it is not sending characters. In other words unless you are actively typing then there isn't really anything except for the voltage being applied to the RX pin that could be causing the board to hang.

So if high logic makes it hang, then why wouldn't 3.3V on a 3.3V input still make it hang?  I'm not saying that using an adapter with a 5V output isn't a problem.  I'm questioning whether there might be two problems — a voltage problem and a logic problem.

(From the little I've read, it sounds as though some chipsets park outputs at a high impedance state, so the input is floating rather than held high or low.)

[danielt]

Basically a TTL serial device "parks" at logic high and will always send out 3.3v or 5v when it is not sending characters. In other words unless you are actively typing then there isn't really anything except for the voltage being applied to the RX pin that could be causing the board to hang.

So if high logic makes it hang, then why wouldn't 3.3V on a 3.3V input still make it hang?  I'm not saying that using an adapter with a 5V output isn't a problem.  I'm questioning whether there might be two problems — a voltage problem and a logic problem.

(From the little I've read, it sounds as though some chipsets park outputs at a high impedance state, so the input is floating rather than held high or low.)

5v is not really logic high (from the Pinebook's point of view), it is over-volting the I/O pins.

So far on the Pinebook Pro forums I have seen multiple independant failure reports with the Pine64 3.5mm serial adapter (over-volting), multiple independant success reports with a variety of different 3.3v adapters (logic high) and, unless I have overlooked something, no failure reports with 3.3v adapters.

3.3v adapters could cause touble (IIRC 3.3v is, strictly speaking, slightly over-volted too... but hopefully it is within engineering tolerances). However if they do cause trouble why are we not getting failure reports for that?

[z4v4l]

(IIRC 3.3v is, strictly speaking, slightly over-volted too... but hopefully it is within engineering tolerances

not accordingly to the rk3399 datasheet, which claims 3.15 V as the acceptable maximum to that power domain.