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General project discussion / help
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By Barbouri
Hi Chip,
I built the programmable voltage reference, and all the hardware is working well.
I have spent an evening trying to figure out how to calibrate manually using the RevD firmware.
Could you possibly explain the serial command structure that was used and how an offset is written?

Thank you for a great and useful project!
Barbouri (Greg)
By uChip
Attached are two documents. One describes the command structure for controlling the reference. The other describes the process of calibration. Most devices would calibrate with a piece-wise linear interpolation, this one uses a run-length encoded lookup table.
Have fun,
Command definition.pdf
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By altitude
hey uChip.

Your board is getting a fair amount of use over here :D Using to calibrate euro modules..

Anyway, I'm up for getting the accuracy to as good as it can be but having some difficulty getting the terminal up and running. I'm running this on a ARM linux distro (lumbuntu/Odroid) with a Adafruit FTDI friend and using PuTTY. I can communicate with the PVR and can see the "voltage reference X.XX" change when I move the encoder but I have 11 instances of "-1:-1" below that value. I cannot enter any commands via the keyboard.

I suspect it something with my setup, I'm somewhat comfortable with PuTTY (I do have it at 115200-8-N-1) but not that familiar with debugging serial connections so any help is greatly appreciated
By uChip
If it's printing out characters in the right format, then the settings for the serial port are probably correct.

How did you program the microcontroller? If you used the Arduino IDE, then I would suggest getting everything working using the IDE's terminal window. When you know things work and have the command set understood then you can switch to the Linux setup. In other words, isolate the various components and test that they work in known environments, then add the unknowns one at a time.

Good luck,
By altitude
I used an Atmel AVRisp2. I dont recall how (avrdude or within the Arduino environment). I also dont think I've updated since my last post here (sept), could that be an issue? It works fine other than the serial thing.

I see the same behavior on windows..
By altitude
hmm. made it worse. tried reloading the firmware in arduino 1.6.8 and now i just get garbage on the serial port (ààf~ff~ff~ff~ff~ff~ff~ff~ff~ff~ffþ when I press the encoder)


dropping the baud rate by half fixed the above but still getting the -1:-1s
By uChip
What about entering commands? If you enter #1234 followed by a carriage return, what happens?

The -1s might just be un-initialized table entries.
By uChip
Does your terminal emulator work when connected to a different device at the same baud rate? If not, then work on the settings until that works.

If the terminal emulator works in other scenarios, then check the wiring on the FTDI. Clearly the output from the Voltage Reference is working, so focus on the input side. Are the lights blinking when you type a character? Does the Adafruit FTDI even have lights? I use the SparkFun FTDI and have had no problems with it, but I have no experience with the Adafruit one.

Keep trying to isolate what works from what doesn't. Hopefully that will lead you to the part that's going wrong.
By yngndrw
This is a really nice looking project. There was some mention of a second version last year but there have been no update since, is this still in progress ?

Please consider selling a full kit of parts, I'd be really interested in this.
By uChip
The second version is well along, but I'm currently being heavily distracted by my day job. I will get back to the reference project eventually but I can't promise when.

I have not received enough interest for it to make sense for me spending the money to inventory and kit the parts. Perhaps it will help if I post an updated BOM with vendors and vendor part numbers. I will look at doing that.

- Chip
By yngndrw
A BOM with vendors and part number would be fantastic, preferably with vendors who can do international shipping. I'd happily wait until V2 to get more accuracy, I know all too well how projects can end up on the back burner thanks other distractions !
By altitude
hey PVR crew, time to dust off this thread a bit..

I use my PVR a lot for calibrating v/oct scaling on analog synths almost daily and since have purchased a proper calibrated meter so now i want to look at the calibration of the PVR a bit closer. I have the serial coms up and running but seem to have some issues on some parts:

I can change the reference voltage with #NNNN, set the global offset with UNNNN, switch back and forth with !NNNN and #NNNN for the reference and and non-adjusted values. So that all works.

What I CANNOT do:

Save the global offset (it clears when device resets)
Write to anything
display the calibration table (shows a list of FF values)

I switched out the uC just to make sure that was working correctly and it was..

Also, my output in PuTTy doesnt match whats in the manual, IE:

When is punch in #1000 this is the result:

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