Rockbox mail archive
Subject: Re: GDB and serial port
From: Andrew Jamieson (ajamiesn_at_mira.net)
Here's a piccie showing an easy spot to pick up both transmit and receive.
You'll be able to note that the transmit line also goes to second 'bottom'
pad on the left of the unloaded SMD component - so that's a good spot to
pick it up too.
From what I can see, you should be able to get away with connecting the
serial lines directly to the line in jack without cutting the connections -
the schematics may not be right for this area, and the micronas datasheet
refers to having simply a cap buffering the input from the chip, so
soldering directly to the connector should be OK. If they have followed the
datasheet, simply removing the caps will actually isolate the connector
anyway, so I'd try this first, before going mad with the X-acto knife!
PS: I'll update the schematics soon. I promise.
----- Original Message -----
From: "Nielsen Linus (ext)" <Linus.Nielsen_at_elema.siemens.se>
Sent: Thursday, February 07, 2002 9:17 PM
Subject: RE: GDB and serial port
> > I'll try and check this for you tonight. A couple of points
> > first tho:
> > * It's possible to organise a half duplex serial
> > connection over one wire, with a bit of circuit trickery,
> > but it would be (a little) more effort than what you are
> > proposing, for less reward. The upside would be that the
> > mod would be non-destructive, and reversible.
> The problem would be that I would have to hack the serial drivers
> in my Linux kernel, and possibly also the gnu debugger. Not the way
> I'd like to spend my next 2 weeks... :-)
> I looked more closely in the schematics, and it may be possible
> to connect the serial lines to the Line In without cutting the
> connection to the MAS. There is a capacitor connected from the left
> ear to GND that may interfere, but i'm not sure.
> I don't care, since I can't think of any use for the
> Line In anyway...
> > * You've probably already thought of this, but you could
> > implement a software UART for transmit, and switch to the HW
> > UART for recieve (so you could accelerate downloads, for
> > instance). This would require no mods at all .... but more SW
> > development.
> Uuuuh. Another week... :-)
> > * From experience, copper winding wire is fantastic for
> > soldering directly to the pins of QFPs like the SH-1 processor.
> > You need to burn off the thin insulating layer (get a blob of
> > solder on the iron, and then push the wire though the blob
> > a couple of times, until the wire 'tins' - ie the
> > insulator is burnt off and the wire looks silver instead of
> > copper) and then just solder it to the pin. You can get
> > this wire in various sizes down to 0.2mm (IIRC), and it's
> > sooooooo much better than thick plastic sheathed stuff
> > (such as wire wrap wire). Trust me.
> Great tip. Thanks.
> > That's it. I'll rip my JB appart now and see if I can
> > determine where the send line goes. Good luck .....
> Good luck to you also! Happy hunting! :-)
Page was last modified "Jan 10 2012" The Rockbox Crew