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robinhedwards / A8PicoCart

UnoCart on a Raspberry Pi Pico clone
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Need for removing cartridge when plugging USB cable #2

Closed jhusak closed 1 year ago

jhusak commented 1 year ago

In the manual: ALWAYS REMOVE THE CARTRIDGE FROM YOUR ATARI BEFORE PLUGGING IN A USB CABLE

What could happened? Was it tested and something happened? How could (cheap way) be this handled not to remove cartridge? Removing and inserting cartridge many times is harmful either for the slot or for cartridge itself.

And in fact not the cable is a problem but adding new 5V power source from the host computer.

robinhedwards commented 1 year ago

The risk is the USB port back-powering the Atari through the cartridge port. There is a diode on the purple pico clone which prevents the opposite happening. Although I haven't tested it, I would say the risk is real and damage is likely to occur.

There is a fuller discussion of the whole issue on the AtariAge thread, and suggestions as to how the board could be modified to remove this risk. https://forums.atariage.com/topic/351546-a8picocart-unocart-on-a-raspberry-pi-pico/

I have solved the issue in the next version of the PCB by rotating the pico through 90 degrees such that the USB port is facing downwards. This makes it physically impossible to plug in USB when the cartridge is inserted.

The atari cartridge port is designed to have cartridges plugged in and removed constantly, so I'm not worried about that. The wear to the cartridge itself is more of a concern, I agree - but this is designed to be a cheap and simple device.

New version of the PCB will be posted on github shortly.

jhusak commented 1 year ago

I think a diode from Atari 5V to pico can prevent any issues. Think of it as developing tool. You develop, upload, test. Without removing a cart. I think it is doable, or maybe I'm missing something?

robinhedwards commented 1 year ago

Have a look at my posts on page 6 of the thread I linked on AtariAge. A diode is not enough.

Robin

jhusak commented 1 year ago

So there is a try with hct4053 :) I'll watch the topic just in case.

robinhedwards commented 1 year ago

New version of the PCB uploaded today makes it physically impossible to plug in USB cable when cartridge is inserted, so I'm going to mark this as resolved.