[time-nuts] GPS message jitter (was GPS for Nixie Clock)

David davidwhess at gmail.com
Tue Jul 19 00:44:19 EDT 2016

The aged 16550 has various timeouts so an interrupt is triggered with
a partially full buffer even if it is below the interrupt threshold.
For implementations which do not do that, I assume they intend for the
UART to be polled regularly.

On Mon, 18 Jul 2016 23:42:34 -0400, you wrote:

>I can't speak for linux, but I have been bitten by FIFO watermark
>interrupts on micros before. If you set an interrupt for a 3/4 full FIFO,
>the last one or two characters will sit in the receive buffer and never
>trigger the RX interrupt. For a command -> response device which doesn't
>have a constant data-stream, It isn't until a PC application resends the
>command sequence that enough characters are in the FIFO to trigger the
>watermark interrupt. The easy fix was to interrupt on any single character
>being available, but would have been nice to have a timeout interrupt on a
>partially full FIFO.

More information about the time-nuts mailing list