ldattach pps assignment stops working after some time

[solderdev]

Hi!

On Lattepanda 3 Delta with BIOS LP-BS-7-S70JR120-CN51G-D and -E:

When i set the line discipline for the on-board RS232 DCD pin to PPS signal (GPS time sync) with sudo ldattach 18 /dev/ttyS0 the voltage pulses on the pin are recognized:

sudo ppstest /dev/pps1

trying PPS source "/dev/pps1" found PPS source "/dev/pps1" ok, found 1 source(s), now start fetching data... source 0 - assert 1689853119.297250850, sequence: 4 - clear 1689853118.349362050, sequence: 3 source 0 - assert 1689853119.297250850, sequence: 4 - clear 1689853119.348166941, sequence: 4 source 0 - assert 1689853120.297024623, sequence: 5 - clear 1689853119.348166941, sequence: 4 source 0 - assert 1689853120.297024623, sequence: 5 - clear 1689853120.346971765, sequence: 5 source 0 - assert 1689853121.295818380, sequence: 6 - clear 1689853120.346971765, sequence: 5 ... time_pps_fetch() error -1 (Connection timed out) time_pps_fetch() error -1 (Connection timed out)

But after some time (one to four minutes) i get timeouts (see above). (voltage pulses still arrive - verified with oscilloscope)

Killing ldattach and starting everything again works - but only for a few minutes.

Testet with multiple distributions and kernel versions (Ubuntu 22.04, Manjaro) on multiple Lattepanda 3 Delta boards.

Found the following, where the issue was BIOS related: https://unix.stackexchange.com/questions/701529/pps-on-focal-20-04-timed-out-and-never-recovers

Could this too be BIOS related?

Best regards