RE: FT232R-based transmitter: different behavior on different USB chipsets

[Denis F. <sa...@ma...>]

Hi again!

I have some progress in my case. After some experiments I was able to take some oscillogramms. I have created them using photodiode, hooked to Mic input and Audacity. 
File is available here:
http://fotkidepo.ru/photo/31491/38326MhaqHKPj0P/JlWm4XwOKE/694381.png

First row is "Power On" signal from original Panasomic remote -- it works Ok
Second row is the same signal issued by lirc on computer with UHCI USB chipset -- It works Ok
Third row is the same signal issued by lirc on computer with OHCI USB chipset -- of course it does not work.

As you see, the signal on OHCI chipset is incorrect. How do you think, what is the cause of this distortion?

Regards, Denis.

-------- Пересылаемое сообщение --------
От кого: Denis Fokin <sa...@ma...>
Кому: lir...@li...
Копия: sa...@ma...
Дата: 12 сентября 2011, 00:52
Тема: FT232R-based transmitter: different behavior on different USB chipsets

 
  
  
Hi!

I have created Albert's FT232 IR-tranceiver using UM232R evaluation board. I do not need receiver option, so only boosted transmitter part is currently implemented and used.
I want to use this blaster with my HTPC to control TV, AV receiver etc. During my work I have tested my blaster on 4 different hardware platforms (2 laptops, my PC and HTPC)
 and it seems, that correct transmitting of signals is only available on platforms equipped with Intel's UHCI USB chipsets. 
While connected to my PC or Intel-based laptop transmitter works fine and is able to control my TV, AV-receiver and even old JVC mini system with "stock" remote configuration files. 
But when I connect blaster to HTPC (Ion based) or to old Laptop (Nec USB chip) with OHCI USB controller, I am unable to control my equipment. 
I have checked IR transmission with CCD camera -- everything is fine. I use the same linux kernel on all devices, same set of config files, ftdi libraries and same sources. 
Unfortunately I have no oscilloscope to debug problem on the HW layer, so I need your advice, how to start to workaround this problem.

Best reards,
Denis
   
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