TX/RX Activity LEDs

[flashjazzcat]

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

 

 

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?

[AtariGeezer]

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...

[flashjazzcat]

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!

[AtariGeezer]

 

An example:

Edited January 9, 2014 by AtariGeezer

[flashjazzcat]

Very nice indeed! Thanks for your help Jay.

[HiassofT]

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

[flashjazzcat]

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.