Enabled internal pullup for CML SYSREF outputs, otherwise there is no signal on them.

[marmeladapk]

Signed-off-by: Paweł Kulik [email protected]

ARTIQ Pull Request

Description of Changes

Without setting driver impedance there is no signal on SYSREF outputs. Figure 20. suggests that we should enable internal 100 Ohms when using DC coupling and no external pullups (altough it's not clear to me what they had in mind in this documentation). I checked that ARTIQ now progresses past "DAC sync failed: no sync lock" + that there is a clean clock on SYSREF intputs with 1Vpp swing. Before that change there was no signal and 0V at sysref signals.

Type of Changes

	Type
✓	🐛 Bug fix

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[sbourdeauducq]

Thanks!

[sbourdeauducq]

I checked that ARTIQ now progresses past "DAC sync failed: no sync lock"

That's still a problem on my board, though...

[marmeladapk]

@sbourdeauducq Could you try on eb271f3? That's the commit that I was testing on. I also suspect that you may need to clk_src_ext_sel or at least use pullup/down. (Though I didn't require it on my board).

[sbourdeauducq]

I also suspect that you may need to clk_src_ext_sel or at least use pullup/down.

Thanks.
150a021
But it's having none of it.

[marmeladapk]

@sbourdeauducq Could you check if you have any signal on sysref outputs and ADCLK948 output?