Since I have a spare Arduino and wanted to have a serial connection with the PS1, I have been playing around with this and was able to make it work. However it was a little less intuitive than I expected, considering how simple the whole process actually is. I tried the schematics on the first post but without luck, and had to do some tinkering to make it work. So I thought I might as well post here what I found out so that I can save other people some time.
Abbreviations I'm going to use in this post to make it more readable:
ARx: Arduino's Rx PIN (PIN 1)
ATx: Arduino's Tx PIN (PIN 0)
PSRx: PS1's Rx Pin (PIN 8)
PSTx: PS1's Tx Pin (PIN 5)
Okay so, PS1 serial port uses 3.3v, but it is possibile to use a standard 5v Arduino after a little setup:
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A jumper needs to be added between RESET and GND on the Arduino to disable the microcontroller and allow use of the board as a USB interface. So far so good.
-- Officially, on the Arduino PIN 0 is marked Rx and PIN 1 is marked Tx on the board and online references. HOWEVER those are not the USB to TTL pins, but the microcontroller's. The following diagram probably does a better job of what is going on here:
psx-arduino-img0.jpg
This means that the way it is marked on the board is actually inverted if we want to use it as an USB interface. That's why
PIN 1 is actually Rx and PIN 0 is actually Tx for our case here.
Knowing this would have saved me a LOT of confusion, as I had my connections inverted for longer than I'd care to admit. Maybe this is common knowledge and I was just being dense, but in any case here it is.
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ARx can be connected directly to PSTx. Even if the Arduino is 5v, ARx is designed to trigger with 3.3v (or at least it should, check it in case), so we're good here.
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ATx needs to be connected to PSRx with a voltage divider. I tried a direct connection (5v), but while it didn't smoke or anything it doesn't allow communications. So we need to lower the voltage a bit with a voltage divider. This is very simple, but the values are a little finicky and required some testing. See the end schematic and resistance values, this gives a voltage of about 3.45v which is a little above 3.3v but seems to be required to make the pin trigger correctly.
Okay, so here's the final schematic I have been using:
psx-arduino-img1.jpg
I have done some testing and it seems to work perfectly! Never had problems with data transmission.
I like that this is a very cheap and reversible method of making serial connection with the PS1, compared to buying a Net Yaroze cable or making one (link cables are getting a little expensive where I live). It is just three soldered wires and that's it. Arduino is probably overkill for this but if you are like me then you probably have one already that is eating dust and might as well use it for something (I ended up buying a dedicated USB to TTL connector just to make things a little more compact though).
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