[Gta04-owner] Switching from RS232 to IrDA for debugging

[Sven Dyroff]

Hello Nikolaus,

any hints which toolchain on which system should be used in order to give 
building your MLO a chance...?   ;-))

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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