UART Hardware Flow Control is broken for #PinePhone 4G LTE Modem 🤔
Source: https://wiki.pine64.org/wiki/PinePhone_v1.1_-_Braveheart#Modem_UART_flow_control_is_broken
@lupyuen
So what's your take on this? It seems UART isn't supposed to be the interface used and the designers intend you to use USB. Why are you trying to use the UART with hardware flow control when it's not wired that way? Of course it won't work unless the bandwidth is trivially low and the system was designed to not block, etc. Does it also not work with hardware flow controll turned off? I'm not an expert, but do own a pinephone.
@poleguy Thanks for reading my posts! :-) Here's the long story...
(1) Yep I wanted to get the PinePhone LTE Modem running with USB on NuttX. I built the USB EHCI Driver for PinePhone:
https://lupyuen.github.io/articles/usb3
(2) But the LTE Modem won't respond when I tried to enumerate the USB Devices. So I want to check over UART whether the LTE Modem is powered up and responding to simple AT Commands.
(3) Actually UART might be sufficient if we're building a simple Feature Phone with Phone Calls and Text Messaging only. (Which is my current objective)
(4) Genode OS managed to get the LTE Modem talking over UART. So I'm trying to reproduce their configuration:
https://genodians.org/ssumpf/2022-05-09-telephony
(5) Right I'm not getting any meaningful output from UART. Thus the troubleshooting continues :-)
@poleguy UART is working now yay! Just realised that the Reset and Power Pins were high-low inverted grrrr...