Add extra INA220 to 12V rail to check presence of crate power

Currently there's no easy way for MMC to check if payload power was applied by MCH.

See https://github.com/lnls-dig/afc-hw/project/ohr-support/issues/234

We may also user the new 3-channel sensors as in #1456.

assigned to @tprzywoz

changed milestone to %AFC v4.0

I AFCZ I added 12V voltage monitor that tells the MMC that voltage is lower than 9V.

Sound good. Any particula reason for choosing 9V?

As this rail is already monitored and controlled by the MTCA PS, detection should be enough for most purposes, so I guess 9V is fine.

any value would work. It's a compromise between short spikes during switching on FMC/RTM rails.

I changed all INA220 to 3 x INA3221 and implemented P12V0 measurement (current from AMC edge connector).

mentioned in issue #15 (closed)

@gustavo.bruno Do you think current monitoring as implemented by Tomasz is enough? Do we need voltage monitoring circut as mentioned by Greg (though it seems that it does not sense for 9V):

we need both current and voltage monitoring. The MMC needs to know that 12V is present.

INA3221 supplies both, right? It should be enough, I don't believe we need the speed of the above circuit. @Greg , you mean we need the extra voltage monitoring or just the usual monitoring provided by the INA is enough?

I'd even argue that voltage monitoring is more important than current monitoring, which is already provided to satisfaction by the PM. IMO, the fast circuit should only be used if we need to free one of the INA inputs.

mentioned in issue #49 (closed)

My colleague from GSI who wrote the MMC firmware wanted to know that power failure will come. In such cases Payload power goes off first, followed by management power. In such case the CPU has time to finish all the FLASH operations without corrupting the memory. I'm not sure if this justifies yet another circuit. THe INA3221 must be connected in sych way that it monitors the payload power even when RTM and FMCs are off.

Yes, INA3221 is a shunt and bus voltage monitor. Each channel is independent during measurement so we will be able to read voltage and current of P12V0 from register all the time. There is a potential problem only with Power Valid Alert feature - because all 3 channels must exceed common limit value - even unused channels. Without RTM we can't use it.

By the way, I changed input pins assignment of INA3221 to keep FMCs signals together. It will be released in v4 community review 3.

@gustavo.bruno @danielot @Greg Can we live with this sort of limitation - we can't have interrupt warning on voltage drop if RTM is not used?

If not we could add comparator to detect voltage loss on AMC_P12V0 with P3V3_MP as reference.

Let's add the detector. We can even make simple resistive divider and use MMC ADC or even pin logic threshold to detect if the 12V is present.

Good, just add a note describing what is the purpose and threshold of this circuit

mentioned in commit c2b15c2f

closed