document postfilter #21

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jbqubit · 2020-12-09T00:24:18+08:00

jbqubit commented

2020-12-09 00:24:18 +08:00

What does postfilter do? What is its default? Minimum and maximum?

Changes in postfilter should automatically so loop filter coefficients can stay the same. #11 (comment)

What does postfilter do? What is its default? Minimum and maximum? Changes in postfilter should automatically so loop filter coefficients can stay the same. https://git.m-labs.hk/M-Labs/thermostat/issues/11#issuecomment-1211

astro commented

2020-12-14 08:26:00 +08:00

IIRC AD7172 postfilter configuration was used for initial noise estimation.

@hartytp How much of that should be configurable at all? What's the prefered configuration?

IIRC AD7172 postfilter configuration was used for initial noise estimation. @hartytp How much of that should be configurable at all? What's the prefered configuration?

hartytp commented

2020-12-15 01:43:50 +08:00

I'm happy either way. It's a nice feature to play with as it gives users the option of making the loop tighter (wider bw) at the expense of slightly more noise. IIRC 10Hz is slower than optimal in the configurations I tested since the noise didn't increase with small increases in the BW (although this depends on how much pickup there is), but it's a good starting point and avoids the complexity of supporting multiple rates.

The one thing I would say is that we should try to keep this firmware as close as possible to the thermostat_EEM firmware.

I'm happy either way. It's a nice feature to play with as it gives users the option of making the loop tighter (wider bw) at the expense of slightly more noise. IIRC 10Hz is slower than optimal in the configurations I tested since the noise didn't increase with small increases in the BW (although this depends on how much pickup there is), but it's a good starting point and avoids the complexity of supporting multiple rates. The one thing I would say is that we should try to keep this firmware as close as possible to the thermostat_EEM firmware.

jbqubit commented

2020-12-15 02:19:29 +08:00

It wasn't clear to me that this was a hardware filter until this comment just now. I gather this relates to register ENHFILTEN0 on AD7172.

This bit enables various postfilters for enhanced 50 Hz and 60 Hz rejection for Setup 0. The ORDER0 bits must be set to 00 to select the sinc5 + sinc1 filter for this bit to work.

It sounds like there are several options related to this register ENHFILT0. In firmware this is called register FiltCon

Best of the README.md says what the high level effect of setting postfilter is. There many configuration options for FiltCon...

It wasn't clear to me that this was a hardware filter until this comment just now. I gather this relates to register ENHFILTEN0 on AD7172. >This bit enables various postfilters for enhanced 50 Hz and 60 Hz rejection for Setup 0. The ORDER0 bits must be set to 00 to select the sinc5 + sinc1 filter for this bit to work. It sounds like there are several options related to this register ENHFILT0. In firmware this is called register [FiltCon](https://git.m-labs.hk/M-Labs/thermostat/src/branch/master/src/ad7172/regs.rs#L228) Best of the [README.md](https://git.m-labs.hk/M-Labs/thermostat#user-content-commands) says what the high level effect of setting ``postfilter`` is. There many configuration options for FiltCon...

astro commented

2020-12-17 01:45:39 +08:00