Bug#640391: ark3116 driver regression: oscilloscope shows no transmission
2011/10/3 ael <law_ence.dev@ntlworld.com>:
>
> As I had suspected from the multimeter measurements, it seems
> that the ark 3116 does not transmit *anything* under the
> latest kernel (on the usual gpsbabel test).
>
> Under the old working kernel, I saw packets in both directions.
> For the record, the gps tx line was swinging between +5.6V and -5.4V,
> while the ark3116 board was driving the gps rx line between 0V and 3.2V.
>
>
> But under kernel 3.0.0-1, I could not get the 'scope to trigger
> on either line, nor could see any activity.
>
> So my conclusion is that the module is somehow setting the ark3116
> into a mode whereby it cannot transmit if only the tx & rx (plus
> grnd=pin5) are connected. Whereas the old version of the module
> sets it up so that this is possible. Agree?
>
> So rather than the gps failing to reply, it seems that the ark3116
> never sends anything.
>
Hi ael,
Excellent work! Thanks a lot.
Initially I suspected either somekind of problem between the USB and
UART parts of the ark3116, or some handshaking mismatch, but from your
experiments I get the impression that the ark3116 is more or less
switched off on the 9-pin side. The fact that there is no response by
the 3.0-kernel to grounding cts is unexpected. There should be a
response to that, even if the actual transmissions are blocked by
handshaking.
The ark I have works with 0 and 3.3V, while RS232 uses -12 and +12 or
so. Usually there is a level-shifter that converts one into the other.
Maybe that part somehow gets disabled by the new driver.
There are some registers in the ark of which it is not clear what they
do. I copied the values and indices from the windows driver for my
ark, but perhaps there is something more suble going on. I'll take
another close look at the old and new driver and see if I can find
anything.
If I find something that way, would a patch against 3.0 be okay for
you? Alternatively, I can make a sort of stand-alone buildable version
of the driver that you can just 'make' and 'insmod', provided you have
the right tools/package installed, if that is more convenient for you.
Groeten,
Bart
--
Bart Hartgers - New e-mail: bart.hartgers@gmail.com
Reply to: