[Gta04-owner] Switching from RS232 to IrDA for debugging
Dr. H. Nikolaus Schaller
hns at goldelico.com
Fri Jul 20 16:44:44 CEST 2012
Hello Sven,
Am 20.07.2012 um 16:31 schrieb Sven Dyroff:
> Hello Nikolaus,
>
> any hints which toolchain on which system should be used in order to give building your MLO a chance...? ;-))
Any gcc which creates working ARM code is sufficient. I.e. gcc 3.3 or later should work. I use a gcc 4.4.5.
U-Boot/MLO tries to be self-contained and not depend on any glibc or linux-headers. Not even the standard C-Runtime.
If you cross-compile, either add the gcc/bin to $PATH or
export CROSS_COMPILE=arm-linux-gnueabi (or whatever the toolchain wants to see)
You should also be able to compile it natively on the GTA04 (using the Debian gcc package), but I have not tried.
BR,
Nikolaus
>
> Best regards,
> Sven
>
>
>
>
>
>
> Von: "Dr. H. Nikolaus Schaller" <hns at goldelico.com>
> An: List for communicating with real GTA04 owners <gta04-owner at goldelico.com>
> Datum: 20.07.2012 15:35
> Betreff: Re: [Gta04-owner] Switching from RS232 to IrDA for debugging
> Gesendet von: gta04-owner-bounces at goldelico.com
>
>
>
>
> Am 20.07.2012 um 14:52 schrieb Sven Dyroff:
>
> Hello Nikolaus,
>
> thanks for reply. As far as I understood the TFDU6301 it's just a simple converter from TTL to IrDA and vice versa.
>
> Not exactly. If I remember correctly the LED makes a short impulse for each (positive) edge it receives. I.e. if you send 11110010000011111 - which would be a start bit and 0x41 = 'A' some logic must generate individual impulses for each 0 to be sent or the LED would not pulse in the correct pattern. This is what I mean switching the UART3 to IrDA mode (there is a control bit described somewhere in the OMAP3 TRM).
>
> So we don't need any IrDA protocol or drivers or other stuff like that. We just solder a cable that connects another TFDU6301 to a TRS3386E and then plug this into a common serial port of our PC. Add some power supply and that's all.
>
> Here, you also need some pulse shaping because the TFDU6301 isn't just a LED and a photo transistor allowing for permanent opertation. This pulse limitation thing is to reduce power dissipation and enhance life-time of the LED...
>
>
> And because a) I remember having read within this list about the trouble of someone other who wanted to try to build his own MLO and b) still haven't managed to come to the end with building QtMoko, I hoped that you could provide the binary...
>
> I think building his own MLO finally worked. There was a git push missing to the server, i.e. the tree wasn't up to date. Please give it a try. Instructions:
>
> http://projects.goldelico.com/p/gta04-xloader/source/tree/master/README-GTA04
>
> BR,
> Nikolaus
>
>
> Best regards,
> Sven
>
>
>
>
>
> Von: "Dr. H. Nikolaus Schaller" <hns at goldelico.com>
> An: List for communicating with real GTA04 owners <gta04-owner at goldelico.com>
> Datum: 20.07.2012 13:55
> Betreff: Re: [Gta04-owner] Switching from RS232 to IrDA for debugging
> Gesendet von: gta04-owner-bounces at goldelico.com
>
>
>
> Hi Sven,
>
> Am 20.07.2012 um 13:36 schrieb Sven Dyroff:
>
> Hello Nikolaus,
>
> I finally want to make my first steps in looking deeper into the GTA04 and therefor I need access to the serial port. After having taken a look into the schematics I still don't intend to open my GTA04 for this reason, because it seems that only one GPIO is to be toggled, so that we can connect _WIRELESS_ over IrDA to the UART of the OMAP.
>
> Is it possible that you build a new MLO that sets this GPIO to zero? So we only need to replace this new MLO with the current one on the SD card and then can debug over IrDA. Whenever we don't want
>
> Yes, changing the GPIO is definitively possible. It should be done in this file:
>
> http://git.goldelico.com/?p=gta04-xloader.git;a=blob;f=board/omap3530gta04/omap3530gta04.c;h=04f310d14e91276f207a524f9ea96b6d12715b9f;hb=HEAD
>
> around line 1100. Maybe, changing the pull-up/down may be sufficient.
>
> But to make it work, I think it is also needs to configure the UART a little differently since the IrDA protocol uses impulse patterns to indicate 0 and 1 states of the serialized data bytes. I.e. just adding a LED to a TX line and switching it on if a 0 is transmitted, doesn't make it IrDA receivable.
>
> anymore to widespread our internal data into our environment for everyone, but want to save some battery power, we just need to replace the MLO again... ;-))
>
> This idea only as a first step. The more better solution would be, that the bootloader switches this GPIO according to the existence of a flag-file like "IrDa.flag" within the FAT filesystem. And of course the best solution would be to have the possibility to set or remove this flag-file with a button, presented by the bootloader...
>
> Well, the MLO could also check the AUX button being pressed, since it is also a GPIO.
>
> But I better like your idea of a special MLO variant, so that you can put it in a SD card you use for kernel work. So it is not necessary to add this feature to any MLO.
>
> One other aspect to consider is that it is not possible to run the full IrDA protocol. Just the lowest level stuff.
> I.e. there is no error correction so you may garble u-boot commands you send to the device...
>
> So you need a special driver on your host-pc as well, that bypasses the IrDA protocol stack.
>
> Of couse I hope that currently the kernel doesn't set this GPIO. Am I right in this assumption?
>
> The current kernel doesn't touch the GPIO, but there should be a driver to enable IrDA from user space...
>
> Nikolaus
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