DPS5015 output inaccurate both on DPS screen and measured on multimeter

[ilium007]

I have compiled for the DPS5015 (v2.3) but output values are inaccurate - see photos.

I set 3.300V - once output is enabled the DPS5015 screen shows a voltage slump to 2.84V and I measure 2.858V

I set 15.000V - once output is enabled the DPS5015 screen shows a voltage slump to 14.100V and I measure 14.25V

Is there anything I can do to fix or have I just created a paperweight?

[ilium007]

I also have a spare v2.4 board that I haven’t touched as yet.

[ilium007]

It turns out my spare board was a DPS5020

But it’s output measured on the same meter is spot on. I’m not confident now putting OpenDPS on the DPS5020 and ending up with two paperweights.

[Xenoamor]

You need to calibrate the device

When you turn it on the screen displays what the ADCs see after it's internal calibration parameters are applied

If you turn it on and the true output doesn't match what you set it to then the DAC calibration parameters are wrong

[ilium007]

Is there a guide for this process?

[Xenoamor]

#120 and #122 are the related PRs that added in the calibration routine. It's done via the communication interface though. There's not a good guide though and I've since moved on from this project

If you don't have a communication interface you can manually set the parameters by pressing m1 + m2 at the same time to get to the calibration screen.. I think anyway

[ilium007]

I’ve just had a look through the commits referenced above and it looks like I understand enough to calibrate. How far apart do the voltage references have to be? Would 3.3v and 24v be far enough apart?

[Xenoamor]

Fair enough, they are almost disposable at the cost they are.

I think the main readme.md could do with a disclaimer, pulling the factory programmed calibration parameters is present in the part 3 of the blog but it's not obvious to people who aren't clicking through to every link

Would 3.3v and 24v be far enough apart

Are you referring to the input voltage, the one that feeds into the back of the supply? If so 3.3v sounds kind of low and I'm not sure it will function correctly with it. I used another DPS to feed my one and used 6v as my lower value and then the max I could output. You'll want to set the current limit to be high

If you're referring to the output voltage then this is a good range yes

[ilium007]

I did save the txt files during my initial flashing ad per the readme. I didn’t realise there were calibration values in there.

[ilium007]

When I try to run dpsctl.py within a clean pipenv that has pycrc and pyserial I get the error below

Both are installed:

[Xenoamor]

I did save the txt files during my initial flashing ad per the readme. I didn’t realise there were calibration values in there.

I've never done this but maybe I recall reading something about it. I just threw on OpenDPS straight away and realised it needed calibrating which is why I added the routine for it

I thought the bug you were seeing was likely fixed in #213 but I guess not. The issue tracker is #215
I can probably look into this when I'm home if you don't manage to resolve it. We don't use pycrc that extensively so if it's just a case of updating the API calls to the latest version then it's an easy fix

If you could give me your pipenv setup commands that would be great as I'm not familiar with it

[ilium007]

Got a bit further tonight, I will try and fix and raise a PR.

~/opendps/dpsctl master*
dpsctl-JB5bKZwA ❯ ./dpsctl.py -d /dev/cu.usbserial-1430 -C
For calibration you will need:
	A multimeter
	A known load capable of handling the required power
	A thick wire for shorting the output of the DPS
	2 stable input voltages

Please ensure nothing is connected to the output of the DPS before starting calibration!

Traceback (most recent call last):
  File "./dpsctl.py", line 1204, in <module>
    main()
  File "./dpsctl.py", line 1198, in main
    handle_commands(args)
  File "./dpsctl.py", line 577, in handle_commands
    do_calibration(comms, args)
  File "./dpsctl.py", line 723, in do_calibration
    t = raw_input("Would you like to proceed? (y/n): ")
NameError: name 'raw_input' is not defined

~/opendps/dpsctl master*
dpsctl-JB5bKZwA ❯

[Xenoamor]

Looks like raw_input should have changed to input when the code was ported to python3

[ilium007]

Thats it. I just made the change on mine

[ilium007]

Raised PR #217