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# Rockbox mail archive

Subject: Re: Jack plug 3.5mm 4 contacts (serial connection)

# Re: Jack plug 3.5mm 4 contacts (serial connection)

From: gizz <gizz_at_online.fr>
Date: Sat, 19 Jan 2002 14:45:20 +0100

Hi all !!

Well, thanks for the links and prices of 4-contacts jacks !!
It can be helpful if one want to build some clean&robust wiring :)

BTW, I don't have indeed one such 4-contact jack at the moment, so if
someone is interested, here is how I connect my PC (via parallel port) to
the NukeBox (oops -- RockBox - wink-wink björn ;) :

I simply used..... a 3-contact jack (!!!!)
The trick is due to the fact that (hopefully) the 2 interesting contacts of
the 4-contact female connector (NukeBox side) are the two first rings of it.

That is, I could link those 2 rings with a normal (3-contact) jack by
plugging it just half the length of it.
Actually, We have to plug the jack so that the two first rings (extremity of
the jack) are totally plugged into the female connector, and also that the
third (the wider ring) remains totally unconnected.
Then, you can connect get the two interesting pins : GND => the second ring;
PB10 => the first ring (the extremity, wich has some strange geometry
(angled etc... in order for the jack to remain plugged firmly)
Then, by software all you have to do, is program PB10 as needed (default is
RxD1 I suppose)
Example : set PB10 as TTL output :
PBCR1 &= 0xFFCF; // PB10 is I/O
PBIOR |= 0x400; // PB10 is output
PBDR |= 0x400; // Set pin PB10 high
PBDR &= 0xFBFF; // Set pin PB10 low
PBDR |= 0x400; // Set pin PB10 high

I know, this description is a full mess, but it's hard to explain..
I joint a pic of the trick, if someone really needs to test the serial port
:)

```--
Gizz
```