PS1 5501 PU-18 rev. 1-644-537-52 random button inputs

[dryja123]

Using the PSUnoRetro adapter from Will's Console Modifications. As soon as I connect the device to my PS1 it starts to spam random button inputs. I factory reset the device and that did not resolve the issue.

Reached out to Will and they said that this is a known issue with certain revisions of the 5501 / PU-18. My board is a PU-18 1-644-537-52.

Opening an issue for tracking.

[darthcloud]

Since a lot of people are now working on making internal PCB for the PS1/2 I thought I'll look into this again.

The PAL machine w/ internal IGR mod that I have got random input issue with one of the of the RS adapter I had.

It doesn't have issue however with my BlueRetro devkit that use those EMI Filters With Integrated ESD on each IO line (basically a 100ohm resistor with two diode to GND on either side of the resistor). The problem is that those filter are so small that they pretty much impossible to work with unless you got a pick and place machine.

Also I think a good practice for the playstation interface is to use 33ohm resistor on all lines. But that itself doesn't resolve the random input issue that my RS adapter had.

I found some bi-directional TVS diode that are big enough to be handle and added that to the RS adapter and it fixed the random input issue on that adapter.

I will update the wiki soon and will make this the way I recommend to wire the ESP32 to the PS SPI interface.

I used a Würth Elektronik 824521500 TVS diode (Digikey part 732-9729-1-ND) this surface mount but is big enough for DIY work.
For a custom PCB you probably want something smaller like a DESD5V0S1BA (Digikey part DESD5V0S1BA-7DICT-ND) (I didn't test this myself however)

I think the important parameters is that it's a bi-directional TVS diode with a Voltage Reverse Standoff of 5V Max

This is probably not magical for all the different problem but it certainly does not hurt to make this the default wiring.

[vsilvalopes]

Hi @darthcloud !
Good to know that we have a solution for those PU-18 with random inputs!
I'm following this thread since I first built my BlueRetro adapter.

I've myself switched to a late PU-8 to use it with Xstation and BlueRetro.
But I can test it on my PU-18.

Can you give me some orientation?
From the schematic that you provide, I undestand that the conections, should be like this:

PS1 Pin > 1 pole of TVS Diode > 33 Ω Resistor > IO on ESP32

1 pole of the TVS Diode to the GND

Sorry about my lack of knowledge, reading eletronic schematics.

Thanks in advance!

[darthcloud]

@vsilvalopes Yes it's correct

Did some test with Will's dongle and it look like we need an extra component to fully remove the random press.

An inline SS34 diode (SCHOTTKY 40V 3A) inline with either the 3.3V or 8V supply (using either supply doesn't look to matter).

I will update the schematic later.

[darthcloud]

Updated schematic with 33 ohm & TVS diode for each IO and a schottky diode on the power input.
I think those 3 measures should fix the vast majority of situation were random inputs can occur.
But it's probably isn't 100%.

https://github.com/darthcloud/BlueRetroHW/blob/master/DIY/PS.pdf