Tuesday, February 10, 2009

Mapping out the Freerunner ALSA sound chip stuff

From GSM chip arrives at RXN/RXP input.

Goes through RXMSEL which configures input as differential or stereo-to-mono. Should probably be differential. This is bit 7:6 of register 30 should be "00". Alsa: "RX Mixer" [RXP-RXN]

There is an RX Mixer mentioned in the data sheet, but I don't see where it is in the diagram. Is it the RM switch?

LM and RM should be set to RXMSEL output. Bits 1:0 of register 2f should be "11". Alsa: Capture Left Mux set to "Line or RXP-RXN"

Left ADC input should be set to LM. This is done with the LADCSEL. Should be set to the output of the RX mixer block. (Register 2e, two lowest bits set to "01"). Alsa: "Capture Left Mixer" set to "Analogue Mix Left"

However, I just get silence (zero samples) when recording.

This is with FSO M5.

Hm. Check the power registers 14h and 15h to make sure everything is on. This does not seem to be the case.

We should then be able to record the phone call.