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flashjazzcat

TX/RX Activity LEDs

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Doing a refit of one of my SIO2SD units (Retr0Brite, new LCD, etc), and I fancy adding activity lights on the SIO2PC component:

 

[attachment=323121:1065.jpg]

 

I did this on a unit I made for AA member Philsan, but that one had an AtariMax SIO2PC in it, with ready-made hook-ups for the LEDs. This one is the standard home-made MAX232/RS232 version. What I have in mind is two additional LEDs on the front: one for transmit, one for receive. Any ideas how best to wire these up to the back of the DB9?

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I think if you tied a 470 ohm resistor on the outputs of the Max-232 that connected to LED's would be fine.  I did a similar mod to my 410 back in '83 and it worked just fine...

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I think if you tied a 470 ohm resistor on the outputs of the Max-232 that connected to LED's would be fine.  I did a similar mod to my 410 back in '83 and it worked just fine...

 

Right - so (bearing in mind I'm a total dunce when it comes to circuits) I just hook the LED's anode to the relevant pin of the MAX232 via a 470Ohm resistor, and the cathode leg to GND? Thanks! :)

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[attachment=323127:merg_led_08.gif][attachment=323128:merg_led_09.gif][attachment=323129:merg_led_11.gif]

 

An example:

[attachment=323130:RS232_adapter1.png]

Edited by AtariGeezer

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FYI: TxD and RxD are at a logic '1' level if idle, so you might want to connect the LED between +5V and RxD/TxD. Otherwise the LEDs are on by default and switched off if some data is transmitted.

Also be sure to use high efficiency LEDs and use a series resistor of some 4k-10k (depending on the LED's specs) so you don't load the RxD/TxD lines too much.

so long,

Hias

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FYI: TxD and RxD are at a logic '1' level if idle, so you might want to connect the LED between +5V and RxD/TxD. Otherwise the LEDs are on by default and switched off if some data is transmitted.

Also be sure to use high efficiency LEDs and use a series resistor of some 4k-10k (depending on the LED's specs) so you don't load the RxD/TxD lines too much.


Thanks Hias - sure enough, this works well. :)

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