[linux-dvb] budget-ci: IR interrupt disabling CI module?

David Härdeman david at hardeman.nu
Thu Oct 26 10:56:49 CEST 2006

On Thu, October 26, 2006 2:16, David Härdeman said:
> I'm currently trying to get a TechnoTrend C-1500 Budget card (using the
> budget-ci module), using a CAM module, working with MythTV.
> After some debugging it seems that it does work fine until I use the
> remote, so if I control MythTV using a regular keyboard...I am able to
> watch channels as normal...but as soon as I push any button on the
> remote, the CI communication dies.

Looking further at the datasheets and the source, it seems that DEBI
address 0x1234 is used when reading the IR command. The address in itself
is quite irrelevant as the IR module has no address decoding so the IR
data will always be present in the high bytes.

However, 0x1XXX addresses are mapped to the registers on the CI module,
and since it only uses the lowest two address bits (see EN50221, section
A.2.2.1), 0x1234 will map to register 0 which is the data register.
Reading from the data register is supposed to be preceded by a read from
the size register, which potentially confuses the CAM (I'm using an
AlpaCrypt CAM, fw version 3.09).

It seems that the windows drivers use the 0x4000 address for the IR read,
which reads the CI hardware version number instead. Perhaps this is a
safer default.

I'll try this approach this evening and see if it helps...

David Härdeman

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