Analogue Joystick Port?

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Atari freak
Atari freak
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Joined: Mon Nov 03, 2003 2:04 pm

Analogue Joystick Port?

Postby AtariOwl » Sun Nov 12, 2017 11:36 pm

Hi Guys

Well the opto coupler worked for the timing system however the transformer did not work as it is for AC circuits and the track is DC.

I then started to look at linear opto couplers and had a little success using IL300 linear optocouplers to generate an isolated response.

HOWEVER.. what i get from the ADCs on the enhanced ports bears no resemblance to the signal out put from the IL300

So i tried putting a resistor in pin 5 or pin 5 and connecting to GND or +5V

What i got was worrying

Unconnected... the value is about 116

Connected to GND the value is not consistent, sometimes it is 20-50 sometimes it is 200-240
Connected to +5V the values are similar.

But there is no consistent direction for the value, and when i attach a scope to the inputs sometimes there is a lot of noise. I know this would suggest that a capacitor would make sense to smooth this somehwat.

Another concern is that sometimes the value does not return to 116 but stays at the extreme value even when the connection is removed.

Does anyone have any experience with the EJP ADCs?

OK interestingly - if i attach it in the following manner

Pin9 (GND) ---- R1 ------ Pin 5 or 15 to read ------- R2 ------- Pin 7 (+5V)

IF i dont connect Pin5 ir 15 and R2<<R1 then i get 5V at the tap. If i connect this to Pin5 or 15 it drops to about 3.3V and Pin5 reads 5. This is at least extremely consistent on either Pin.
If R1<<R2 then it all drops to GND which one would expect but Pin5 still reads 140

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