PGA308: Multi-cal system does not calibrate during pre-cal within acceptable tolerance for our UUT which contains a pre308 gain stage, and a post308 gain stage in the loop

Hi Brett,

Is this the same behavior as in your other E2E post here, where the calibration works correctly without the gain stages, but fails with the external gain? We may need more detail on the problem if not. 

Hi Brett,
I wanted to check in on this, since it's been a while with no response. Did you manage to find a solution to this issue, or was there additional support you needed from our end on this?

Brett

We haven't heard back from you so we assume you were able to resolve your issue. If not, post a reply below, or create a new thread if this one has timed-out.

Thanks
Dennis

Hi Dennis! Sorry I was away on business.
We were able to get past the issue by re-installing the multi-cal software.
We do not under stand why we end up having problems and a re-install works.. the only thing I can think of.. is
an engineer may have been hand editing the sensor model file from time to time and then the multi-cal software get's upset

I do have a question though,

I was wondering if TI had the 1 wire C library used for the PGA308 or a reference to such code so that I can attempt
to use a microcontroller to control the multi-cal system Or any suggestions of such topics you may have.

I am trying to to decide if it would be in our best interest if we used our own microcontroller board to run the multi-cal system
because we would like to use C# or python to do our GUI for calibrations, and would also like full control over any embedded code
to perform said calibrations;

I was hoping there was more under neath the lab view source code for the multi-cal, more of the API for the multi-cal and PGA-308 if that makes sense. I'll have to take a look deeper. Visual basic as well is tough since it's VB6 and no one has a copy of that anymore.
(VB6 was my favorite by the way, wish I had a copy!)

Hi Brett,

We're actually in the process of some revisions to the LabVIEW version Multi-Cal software, but this may take some time. Would a simple Python API for the multi-cal system itself be enough as a starting point for you, or would the Python implementation need to support the full calibration process that the LabVIEW version performs? A simple API should be a fairly straightforward project, but a reimplementation of the multi-cal system in Python would be a more extensive project. 

As far as the 1-wire protocol is concerned, I believe that the PGA308's 1-wire interface is UART compatible at baud rates between 4.8kbps to 114kbps. I don't think we have any example microcontroller code, but the protocol itself should be fairly standard. 

Hi Alex, you know I used to live in Tuscon back in 2008! too bad all the jobs evaporated then.

When we use this in production and we start to ramp up,
we may need to customize the software under our control,
some of the aspects of the multi-cal software may not be important to us,
and lab view, although very powerful, would be a big project to maintain.

Easier if we just had an API and use python or C# but then again
Does TI have an MBED os board? I am using the mbed for several projects. so I was thinking about just using that and making a custom board for the purpose.

1. For now I think a python API, or Visual C# would be just fine to control what essentially I call the MUX. (master and slave) i.e. dut power on off, which mux to select (including slaves) and hopefully an easy 1 wire protocol, non specific or perhaps another layer specific to the 308 if you got it.

If you could expose that or show that source code, I am thinking it would help us investigate whether it's worth moving over to a custom software solution.

- Brett Werner

Hi Brett,
Small world!

I couldn't find any mention of an MBED board from us, but I'm not as familiar with our microcontroller offerings - it's possible someone in the microcontrollers or embedded software E2E forums might know more. From what I was able to find, there may be some community projects trying to port MBED to the TIVA microcontrollers, but beyond that, I'm not sure.

I'll try and get a Python API for the multi-cal hardware off the ground here in the next week or so. I think for the basics, it shouldn't be too difficult, but I'll let you know if we hit delays. I'm planning on targeting Python 3.4, but if you have a strong attachment to 2.7, let me know and I can adjust to support it. That should give you control over DUT power, muxing, 1-wire comms, and access to the USB-DAQ ADC for measurement, if desired.

Hello Alex,

Brett has been helping with the TI Multi-Cal-System to program PGA308's. As Brett stated we have a pre-amp gain of 14.33 and a post amp gain of 2. It seems that the iterative approach used by the software to calculate gain will typically overshoot expected values due to the post amp gain of 2 not being accounted for. We are successful sometimes but usually the error is unacceptable, especially the zero value.

We really need to resolve this by modifying the source code.

Please review and comment.

Thank you,

Brian Poutre'

Hi Brian,

We do provide the source code for the PGA308 Multi-Cal system here, though modifying it may get a little convoluted. We're working on updates to the LabVIEW versions of the PGA308 and PGA309 Multi-Cal, but we don't have an expected time-frame for it yet. A Python API for the multi-cal system is also in progress - a module for communication with the USB DAQ is complete, and modules for the Multi-Cal system itself should be finished soon (likely next week). It would take more time, but we could look into developing a python version of the multi-cal utility. This would have to be command line only, and would probably take a few more weeks to get up and running.