First set of Sampler samples after powercycle invalid

[nkrackow]

Bug Report

One-Line Summary

After a system powercycle (un- and re-plugging 12 V on Kasli), the first set of Sampler samples are invalid.

Issue Details

Using the artiq_sinara_tester script right after a powercycle leads to +10 V on all input channels with nothing connected to Sampler and the test therefore fails. The second set of samples is valid (0 V on all channels if nothing is connected or 1.5 V on one channel if this is wired up to Sampler). Restarting the tester script without powercycling yields valid samples on the first set.

Steps to Reproduce

1. System with Kasli and Sampler
2. Nothing connected to Sampler
3. Run tester script right after powercycle

Expected Behavior

0 V reported on all channels.

Actual (undesired) Behavior

10 V reported on all channels.

Your System (omit irrelevant parts)

• Operating System: Debian
• ARTIQ version: tried with ARTIQ v6.7665.83af3b75 and ARTIQ v6.7621.d9b01ed8
• Version of the gateware and runtime loaded in the core device: gateware ident 6.7665.83af3b75
• Hardware involved:
  • Kasli V2.01
  • Sampler V2.2

[dnadlinger]

Should we work around this in gateware by just triggering one acquisition on reset?

[jordens]

We should first figure out the cause for this.