It's a breadboard with an extender for a Raspberry Pi's pins flipped upside down, a Raspberry Pi Pico, jumper wires, and a clip that came with a CH341A that suffers from the issue of being 5V.
The issue I think would be length of the wires.
Any thoughts? I'd consider soldering something together but I don't have a soldering iron that would be great for something so small and I'm working with what I have on hand.
I also have a Raspberry Pi 4 and the CH341A that has the voltage issue if anyone has a better idea that might work.
I'm guessing it's either an issue with the latency or internal resistance of the wires (as someone else mentioned) so unless I'm cutting and splicing the wires I don't think that will matter
The length of the wire is actually more an issue of capacitance and interferences. But these issues are easily mitigated by reducing the spi speed
A long wire is an antenna that will gather electromagnetic noise from the air and turn it into random signal on the line. Shorter wires will be less responsive and therefore less noisy, and you can also mitigate the problem by grounding everything properly. It's also possible that with the wires in that parallel ribbon, they may induce crosstalk on each other. If you want to be really careful, you could replace that big ribbon cable with an STP cable and ground the shielding jacket.
Also, a noisy/low quality power input to the Pi will produce noise in its circuits and ultimately the output. If you can, supply the power from something better than a wall wart.