is the voltage for uart in LSI 5v 3v3 or 1v8?
You can check the hw user manual here: http://www.96boards.org/documentation/ConsumerEdition/HiKey960/HardwareDocs/HardwareUserManual.md
All 96Boards with 40 pin LS connectors (CE, EE, TV, IoT) are interfaced using 1v8 logic.
The only devices that use 3v3 logic are IoT boards with 30 pin LS connectors and I think that, right now, only the BLE Carbon uses such a connector.
Will a logic level shifter work for uart and what uart pins are used for aosp?
Logic shifting is possible and is actually pretty easy for UART. The signals are fairly slow and since the signals are unidirectional designing the shifters is easy.
I'm lazy so I used a bi-directional shifter in my lab but there is no need to do this. Note that when I'm working at my desk I use an integrated 1v8 USB adapter (hand made level shifters/adapters tend to be a little on the fragile side for me).
can someone confirm if uart is working with aosp on the 960 without the official uart bridge?
I haven't tried but I can assure you there is no particular "magic" in the 96boards-uart. It is a fairly common FDTI part and has an on board voltage regulator to generate the signal levels.
The only bit you might like to take note of is the "on board voltage reference"... if you are using an adaptor that requires a voltage reference you might like to check with a multimeter that the voltage reference is actually there (we have seen problems with prototypes of another board where the Vref pin wasn't active).
HelloYes ric, I confirm. You can use TTL-232RG-VREG1V8-WERegards