[Gta04-owner] GPS fix?

Dr. H. Nikolaus Schaller hns at goldelico.com
Wed Nov 16 12:37:31 CET 2011


Am 15.11.2011 um 14:46 schrieb Neil Jerram:

> On 15.11.2011 13:40, Dr. H. Nikolaus Schaller wrote:
> 
>> 
>> But the module starts sending NMEA records (with 0 satellites and void
>> location data) on /dev/ttyS1 as soon as you give one  impulse on the
>> on/off line.
> 
> Yes, I'm seeing these.
> 
>> Please compare (slightly updated):
>> 
>> 	http://projects.goldelico.com/p/gta04-kernel/page/GPS/
>> 
>> This has been tested by the GTA04-Tester for all units we have
>> shipped so far.
>> So it is safe to assume that the RX/TX interface is working if there
>> is a "ok" record
>> in the test protocol.
> 
> Agreed.
> 
>> What test did not check is if the internal antenna switch and power
>> supply is working
>> well enough and does not have too much attenuation for good reception.

I think I have found the root cause. The VSIM LDO is simply not switched on
or has been switched off by the Kernel regulator drivers.

VSIM should be set to 2.8V. This voltage is provided to both, the internal
and the external antenna.

It is explicitly switched on by the "gps init" command of U-Boot,
and all antenna tests had been done through U-Boot. In the kernel
and GTA04-Tester we only check if the GPS module sends NMEA.
But if the antenna does not have power it can't ever find satellites...

One more test: if you connect an external antenna and

	cat /sys/devices/virtual/gpio/gpio144/value

remains a "0", there is no power...

I will look into the kernel code and there will soon be a new hw-validation kernel
release that has the AUX button and some other minor issues fixed.

Nikolaus



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