MCC128 - dirty Pi power & requesting hardware settable SE/DIFF

[nevan]

I am reaching out to MCC to provide some feedback on the MCC 128 and ask for your suggestions, please.

We are using the MCC128 in a portable application with three biomedical sensors and are encountering two issues:

1. The software settable single vs double sounds nifty, but in reality, we have experienced issues with the hat not always receiving the command during software launch. This is not a setting that I would anticipate changing once a system is built, so for us it would be greatly preferable to have reliable dip switches.
2. Unlike the USB 230, the MCC 128 does not provide a +5 V line, therefore we took our power from the PI’s bus. Unfortunately, we discovered that the Pi injects enough noise that it just obliterates our smaller signals. We now find ourselves building custom circuitry, particularly to condition the power from the Pi.

Regarding point 1, is there a good way to ensure that the Pi receives the setting command, without having to set-check-reset as needed?

Point 2 is actually a big product weakness, given the idea that the MCC 128 should enable freestanding applications, where there are no convenient linear power supplies on a bench. Do you have any recommended off the shelf solutions? Or should we proceed with building something custom to condition power?

Since MCC is quite near to us, we would be very happy to stop by, show you what we are doing and discuss!

Edited February 7, 2023 by nevan

[Fausto]

Hello @nevan.

Thank you for your feedback and suggestions.

The AnalogInputMode and AnalogInputRange enums should be set only once and at the beginning of the application.

https://mccdaq.github.io/daqhats/c.html#c.AnalogInputMode

The settings should not change unless you exit the application.  Are you stopping and restarting your application frequently?

With regards to a +5V power supply, MCC does not have a list of off-the-shelf power solutions, so proceed with your custom conditioning power circuit.

Regards,

Fausto

[nevan]

Good Evening,

Yes we do how to set the Mode and Range, however, we do start and stop the application. When I build a system, these are pretty fixed parameters as a function of the connected devices, so I would strongly recommend that these be made persistent.

The lack of stable power is something that we did not realize would be an issue, until we found out that that the Pis create noise. I assume that the USB 230 has internal conditioned power and does not just draw form the USB. This really, really needs to be addressed with the MCC 128 in a V2 product.