Use OsmocomBB as OpenBTS / airprobe clock generator
laforge at gnumonks.org
Sun Apr 11 05:37:05 UTC 2010
On Sun, Apr 11, 2010 at 01:28:27AM +0200, Steve Markgraf wrote:
> >Ideally, we would even use the Calypso-internal PLL (for ARM or DSP) to
> >multiply it up to the required 52 MHz. However, neither the Openmoko
> >nor the Compal/Motorola phones expose any of the 3 clock output pads :(
> Hmm, 3 output pads? I only see DPLLCLK and CLKOUT_DSP, the third one
> would be CLKX_SPI, but can that one be used for this purpose?
The third one is MCLK, i.e. the clock that the Calypos PLL feeds into
the ARM core.
> I looked at the Motorola W220, which uses the DPLLCLK-pin as TSPACT5
> wired through a buffer to GSM900_TX of the antenna switch.
> The pin on the buffer is quite well accessible, so we could tie it
> to low (and disable TX with that, but we don't need that anyway,
> right?) and use VC1B as clock output.
Yes, I agree, this should work just fine. However, using the Altera
internal PLL to multiply from 13 to 52 sounds even better!
> Our code already runs on the W220, but we would need a driver for
> the Si4210 GSM transceiver.
That doesn't sound hard. Didn't you say that you have documentation?
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
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