UART problem when data is already arriving during boot

For discussing issues specific to Linux Device Tree implementation/use on the Raspberry Pi and Compute Module products.

2 posts
by basj » Tue May 16, 2017 9:21 pm
I'm using UART Rx since years, because of the project I started :, to add a MIDI IN to the RaspberryPi. I wrote this guide 2 years ago. The new method:

Code: Select all

works great :), far better than the old hack with init_uart_clock=2441406.

But I noticed a UART bug in the new version:

* When RPi boots, and receives no serial MIDI data during boot time, everything works, the MIDI arrives correctly

* When RPi boots, and receives serial MIDI during boot time (for example because RPi is connected to a drummachine already ON, already spitting MIDI sync messages to RPi), it doesn't work : further use of MIDI won't work.

Any idea?
Posts: 14
Joined: Tue Mar 03, 2015 1:37 pm
by PhilE » Thu May 25, 2017 4:37 pm
I think uart0 (ttyAMA0) has a problem when the line isn't idle and it is started - it loses synchronisation. ttyS0 doesn't seem to have the same problem, but there isn't a midi-uart1 overlay for it, so I'm working on one.
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1119
Joined: Mon Sep 29, 2014 1:07 pm
Location: Cambridge