Hi Steve,
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.
see: http://www.steve-m.de/projects/osmocom/w220_dpllclk.jpg
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?