Alternate PCBs for gusmanb/logicanalyzer
BOM for the peeko & level shifter
DigiKey cart
peeko_and_level_shifter_digikey.bom.csv
The order you solder the parts matters.
Solder everything on the Pico side first, but not the Pico itself, just the pins, diode, resistor.
Then flush cut the bottoms of the Pico pins, at least where the IDC connector will lay.
Then solder the bottom side parts. No need to flush cut any.
Lastly solder the Pico to the pins and flush-cut the tops.
For the fly wires, peel 10 wires off the female jumper cable to leave 30 wires together.
Cut the ribbon in half right in the middle, try to cut at exactly 90 degrees.
Crimp the 30-pin female IDC connectors on the cut ends to make 2 6-inch cables.
Or cut closer to one side to make a single longer cable.
Or remove both the cable and the IDC connectors from the cart and here is another option for a pre-made fly wire cable:
https://www.digikey.com/en/products/detail/digilent-inc/310-064/5848557
For mini-grabbers, they are expensive on digikey so they are not in the bom.
If you enjoy being miserable:
https://www.amazon.com/DIYhz-Colors-Grabbers-Electronic-Experiment/dp/B07BCZSNGS
They are really terrible because the metal is weak and the hooks fall off.
If you are rich, then why are you here instead of just buying a proper DSLogic?:
https://www.amazon.com/Micro-Hook-Double-Grabber-Test-Connector/dp/B00R3R7IVC
These are good but that would be $100
These are good. Not as fine tipped as the E-Z Hooks, but small enough for 0.1" legs. Pretty good construction and operation.
https://www.amazon.com/Goupchn-Grabber-Analyzer-Electronic-Testing/dp/B09TPBS7YF/147-7256223-7410705
A version with the txu0104 level shifters built in.
The VREF jumper lets you select either 3v3 or 5v inputs,
or you can supply 1.1v to 5.5v VREF from the target to the VREF pin for 1v8 or 2v5 etc.
A re-drawn version of the Jason Yang board with simple resistor-diode level shifting and clipping.
The good thing about this one is it clips as well as level-shifts, and it can handle both higher than 5v and lower than 0v, so you could read rs-232 for example.
But the higher the input voltage, the higher the current load on the target.
I think this design must be pretty abusive to both the RP2040 and the circuit under test.
5v input probably means about 4.5ma load on the target, and you're still overdriving the pico input to about 4v.
12v input probably means about 36ma load on the target.
-12v input probably means about 50ma, and passing about -1v to the pico input.
I have not tested to verify if it's actually as bad as these estimates.
Some options to maybe help:
Maybe swap out the BAV99 for BAS7004 for faster switching time and lower forward voltage.
Maybe swap the 220 ohms for 470, 1k, even 4.7k if you don't need the full 100msps.
But the full 100M samples/second is only good to about 10mhz signals already, so you don't want to lose much more.
Higher resistance means less current so you can read higher voltages, but also means slower rise time.
For software, firmware, & directions, see gusmanb/logicanalyzer