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RafaelLeeImg
@RafaelLeeImg
DSC_7304_retouch.jpg
I remove all the big capacitors, after I solve the discontinuous oscillation problem. I think the overall performance will be good.
Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]

One issue I ran into with this I2C sensor:
https://github.com/tasmota/docs/pull/954/files

The docs led me to believe the boards had the same pin order.
I.e., I had GND and SDA swapped.
Anyhow, there's still nothing detected. I will see if it works with an ESP board here when I have the time.

Alexander Bessman
@vgfsrhkbgd:matrix.org
[m]

Could be because of:

Only a single AHT10 can be connected to the I^2^C bus and no other I^2^C devices can be connected.

The pslab's I2C bus also has the mcp4728 on it, as well as the rtc if you're using the v6 prototype.

Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]
ah dang, right... I think I've actually tried having only the AHT10 on the v5, will recheck
I2C things can be so stupid sometimes xD
Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]
Can't get it to work. But I do have some progress with the libusb WASM port and managed to build it somehow. Not sure how to integrate it just add.
https://twitter.com/OrangeCMS/status/1507728538782384135?t=mH_mtIOMvLb4zebfKWwRQw&s=19
For FOSSASIA Summit, I will merely have a draft, not even a PoC, I think. I know that it's doable, it's just complex unless you've done it already. ^^
RafaelLeeImg
@RafaelLeeImg
in-,out.bmp.png
The actual wave form output I measured for the LM833, the last stage for variable gain amplifier.
20220326-234303-simulation1.png
RafaelLeeImg
@RafaelLeeImg
This a simplified amplifier simulation graph, the main cause of oscillation is C4, which is introduced by MAX5400 pin input capacitance. This leads to uneven frequency response. Add with other distributed parameters, this will cause oscillation.
20220326-234334-simulation2.png
Modify C4 to 0pF, the frequency response is flat. But this cannot be done in physical world.
RafaelLeeImg
@RafaelLeeImg
20220326-234602-simulation3.png
Add R4 and C3 to simulate another stage of phase shifting, the oscillation starts.
RafaelLeeImg
@RafaelLeeImg
20220327-000348-simulation4.png
Add C5 to 5pF to compensate the C4. The voltage devider of R3//C5 is the same with C4//R1, in this situation, the frequency response is flat.
Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]
And I've released a new version of Fiedka the firmware editor, https://fiedka.app/
it can now edit and save UEFI based firmware, and also analyze AMD PSP and coreboot filesystems 🐙
Michael Deffner
@Co_eus:matrix.org
[m]
Hey everyone, I'm having some troubles with a project & pslab python library, is it fine to ask some questions here or can you point me to the right place? You work is awesome, by the way 👍️
Alexander Bessman
@vgfsrhkbgd:matrix.org
[m]
This is the right place to ask.
Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]
I've updated the issue on WebUSB, libusb, Sigrok, monorepo and what I'm experimenting with:
fossasia/pslab-desktop#697
Michael Deffner
@Co_eus:matrix.org
[m]

I'm want to test transmission through diy guitar effects, so pslab wavegenerator -> some device -> pslab oscilloscope, everything automated via python. I can of course send sinusodial signals (one frequency at a time) from the waveformgenerator to the oscillopscope, but that's inefficient. One could do a sinus-sweep through the audible spectrum or use white noise.

This is how I basically create my waveform:

from pslab import WaveformGenerator
wavegen = WaveformGenerator()
wavegen.load_function("SI1", lambda x: 0.5*np.sin(x), [0, 2*np.pi])
wavegen.generate(channels = 1, frequency = 100)

I don't understand how exactly the frequency enters the formula. For a sin-sweep, I want to modulate the frequency with another sinusodial function with a low frequency - but in the lambda function above the frequency is not stated explictly. Is there a way to pass something like this to load_function:

def myfunction(frequency, phase, time):
    return np.sin(frequency * time + phase)

Another way would be to somehow generate whitenoise from one output...that would basically mean I have to replace the sin function with np.random.random()or something...but there I have the same problem, that I don't understand exactly how the frequency and timestep is passed to the function.

I hope this is understandable, and thank you so much in advance!

Alexander Bessman
@vgfsrhkbgd:matrix.org
[m]

To load more complicated functions than the load_function method allows (such as functions of more than one variable), you can use the load_table method instead. It let's you load a 512 values long list into the pslab's memory, the values of which the pslab will do its best to reproduce when you call generate. It loops over the 512 values every 1/frequency seconds.

However, the pslab is not able to accurately reproduce signals that contain harmonics above 5 kHz. You can try to load 512 values from np.random.random into memory and see what you get, but I'm not sure how good the result will be. It's definitly an interesting experiment!

1 reply
Alexander Bessman
@vgfsrhkbgd:matrix.org
[m]
Please let us know what the result is and if it does what you need it to do!
apoorva-raj
@apoorva-raj
@vgfsrhkbgd:matrix.org Can you share the shipping details of the PSLab hardware so that I can track the package?
Alexander Bessman
@vgfsrhkbgd:matrix.org
[m]
It's not traceable. Swedish postal service doesn't offer traceable shipping outside EU.
MOHIT GUPTA
@MohitGupta121
@apoorva-raj I also want that for testing hardware what's procedure for that?
Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]
I won't join this Saturday, since we're having spring(); break(), an event at the Bochum hackerspace Das Labor, just FYI.
So we'll meet again at FOSSASIA Summit. 🥳
Alexander Bessman
@bessman
Getting a 404 on the meeting link.
Padmal
@CloudyPadmal
Same here..
Mario Behling
@mariobehling
sorry, missed that.
We updated the system and links got changed
apoorva-raj
@apoorva-raj
Alexander Bessman
@vgfsrhkbgd:matrix.org
[m]
I won't be able to join the meeting today. I have a few points I had intended to bring up:
  • Building the firmware with cmake works now (fossasia/pslab-firmware#132).
  • It depends on https://github.com/Elemecca/cmake-microchip as a submodule. We should fork that repo under the fossasia github area in case it gets deleted or something.
  • I suggest we split the pslab-firmware repo. The contents of pslab-core.X should stay in the current repo while the contents of pslab-bootloader.X should go into a new pslab-bootloader repo.
Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]
This is marvellous, almost 25k lines of junk dropped!
Alexander Bessman
@vgfsrhkbgd:matrix.org
[m]
Well, the "junk" is mostly the MCC configuration, which we no longer need but did need in the past.
It's wasn't even needed for building with MPLAB, only for running MCC which we did a couple of times right at the start of the firmware overhaul. So we could have removed it a while ago.
Daniel aka CyReVolt 🐢
@CyReVolt:matrix.org
[m]
Alexander Bessman
@bessman
Hi @mariobehling, could I have write permission for https://github.com/fossasia/cmake-microchip, please?
Mario Behling
@mariobehling
@bessman done
Alex L
@alexl:kde.org
[m]
Hi all, is it possible to connect two smartphones with Jack audio, use PSLab app as wave generator on one device and view it in the oscilloscope on the other one?
Padmal
@CloudyPadmal
Hi @alexl:kde.org , we haven't yet finished the work to make PSLab use audio jack as a wave generator output fossasia/pslab-android#1976. So it's not possible at the moment.
1 reply
Alexander Bessman
@bessman
I just flashed firmware to the PSLab using nothing but Python :)
Padmal
@CloudyPadmal
Wow! That's super cool!! 😎 I wanna hear more about it
I originally wrote this as part of pslab-python, but realized that it's generalizable to any device running Microchip's 16-bit bootloader. So I split it into a separate package. I'll add it as a dependency for pslab-python.
I also need to add some docs and tests.
Padmal
@CloudyPadmal
I just checked and it looks pretty cool!
Mario Behling
@mariobehling

https://twitter.com/mariobehling/status/1531119488556355584

PocketScienceLab dev @bessman

released #mcbootflash a #Python #FOSS #OpenSource tool for flashing #firmware to devices running
@MicrochipTech's MCC 16-bit bootloader. Can be automated and used as a library. https://github.com/bessman/mcbootflash