Any brave dive computer download testers out there?

Linus Torvalds torvalds at
Wed Apr 18 16:50:17 PDT 2018

On Wed, Apr 18, 2018 at 4:18 PM, Linus Torvalds
<torvalds at> wrote:
> Hmm. Which IRDA chip is it that is in the Uwatec dongle?
> Is it perhaps the MosChip MCS7780? You'd know, because then it would
> be using USB ID 9710:7780. That seems to be the common case.

Hmm. Googling around, I see that it might also be the Sigmatel
Stir4200 (USB ID 066F:4210).

That actually has better documentation, and shows exactly the framing
for the normal MIR format (which it would be for the normal 9600
baud). I suspect the MCS7780 needs that same format, it's just not
documented as well.

The packet wrapping looks like this:

    0x55 0xaa 2-byte LE length, 0xC0*n  .. escaped data .. 2-byte LE CRC 0xc1

and from what I can tell, the Stir4200 also resets to sane default
values (9600 baud SIR).

But you may have to do some USB control transfers to set the data
direction. It *looks* like the MCS7780 is simpler and defaults to just
"automatic data direction" (which presumably just means "send if there
is TX data, receive otherwise").


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