No signal in output

[ilyamordasov]

• Ordered a pcb from oshwlab FScope 250k5-V2 and soldered according to BOM list and schematic. When I connected generated signal to ch1 I got nothing in scoppy app. Also if I disconnect wires the signal is not changed, but if I select 1.25 MHz square signal I see the noisy line with increased frequency, but it doesn't look like square signal, even f I select sine signal. Where could be a problem? I use scoppy-pico-fscope-250k5-v14.uf2 firmware

[fhdm-dev]

Does the oscilloscope work if you apply a DC voltage to the input directly? If not then you'll need to check all the voltages from the input to the Pico ADC to find out where the problem is.

[ilyamordasov]

Unfortunately I don't see negative voltage. Pin 1 and 4 give me 0.49v, bnc 1.65. Also I checked u5, where I expect to get -2.5v, but I get 0.15v

[ilyamordasov]

Also I checked vsys pin, it has 0.25v, guess it is too low. When I tied vsys to 3.3V, I got my signal in output

[fhdm-dev]

Yes - that's way too low. I would expect VSYS to be about 5V. If connected to a phone the actual voltage will depend on the charge of the battery and could range between 4.5V and 5.5V.

[ilyamordasov]

I checked with phone and tablet, in both cases vsys is equal zero. Maybe because the dev-kit is clone from AliExpress. So, I think I will use it with connected to 3.3V. Is it possible to measure the signal, let say, 10V, for example, using your kit?

[fhdm-dev]

I'm not sure the board will work correctly with 3.3V on VSYS. You might see some clipping of the signal....Sorry but I don't what dev-kit you are referring to.
You can use the FSCOPE board with 10X probes to measure voltages higher than 6V. You can change the probe settings in the app by tapping the channel badge at the bottom of the screen, then tap Settings and then Probe.