Posted By
Z9leca
on 2023-08-12
14:50:57
|  Using C16/Plus 4 joystick ports as input pins from a microcontroller
Hi everyone, and thanks for caring for the 264 machines.
I have a little project in mind where I want to send dats to the C16/Plus 4 from a microcontroller. As the C16 doesn't have a user port and (at least in some articles I found - please correct me if I'm wring here) the Plus 4's user port doesn't seem to be capable of receiving data on the user port I was thinking of utilizing the joystick port(s). Has anyone done anything similar?
I have been digging around quite a bit on the internet but failed to find any conclusive information.
Thanks in advance
Carl
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Posted By
SukkoPera
on 2023-08-12
15:04:44
| Re: Using C16/Plus 4 joystick ports as input pins from a microcontroller
> the Plus 4's user port doesn't seem to be capable of receiving data on the user port
Sorry?
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Posted By
z9leca
on 2023-08-12
15:48:18
| Re: Using C16/Plus 4 joystick ports as input pins from a microcontroller
Oh, excuse me. I browsed around a bit more and saw one of your projects that obviously proves that wrong.
I am however quite certain I read somewhere that something wasn't wired completely/correctly in the Plus 4 user port, resulting in an inability to set the port pins to read. Bad source, obviously.
The question remains however, as it'd be nice if I could use my solution on a C16 as well as a Plus 4. But, after reading up a bit more on the broken latches on TEDs maybe I'm barking up the wrong tree here?
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Posted By
BSZ
on 2023-08-12
16:29:20
| Re: Using C16/Plus 4 joystick ports as input pins from a microcontroller
The user port can of course be used as input. Set the port bits/pins to high, this high level can be pulled low by an external device. The current status can be read from the port register.
Using the joystick port for GPIO is unfortunate; it can only be used as input, not as output at all.
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Posted By
SukkoPera
on 2023-08-12
17:26:45
| Re: Using C16/Plus 4 joystick ports as input pins from a microcontroller
Yes, the user port works perfectly of course. The only gotcha is to release all keys on the Datassette or bit 2 of the parallel port will always be low.
I think a practical way of exchanging data between the +4 and a microcontroller is by using the serial port that is part of the user port: if your MCU runs at 5V (or if it is 5V-tolerant) you need nothing inbetween.
It's true that that wouldn't work on a C16, but maybe my 16UP project will help :).
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Posted By
MIK
on 2023-08-13
04:29:53
 | Re: Using C16/Plus 4 joystick ports as input pins from a microcontroller
There was once talk about using a Plus/4 as a midi controller, I don't recall anything being made but midi in/out could do the same thing.
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Posted By
SukkoPera
on 2023-08-13
06:06:33
| Re: Using C16/Plus 4 joystick ports as input pins from a microcontroller
This is the MIDI thread: https://plus4world.powweb.com/forum/46303#46354
The board works very well by the way, it hasn't been released yet just because it's supposed to be at the same time as a game by chizman but unfortunately he's busy and he can't finish it at the moment.
The original design was meant for MIDI output only though, adding the input circuit was my choice while I was designing the board. I do not have many ways of testing it but it seems I can receive the serial data, so it should be good.
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