I finally got a BBGW to do some testing. The results aren't what I expected:
First of all, the analog outputs work fine for me. Output is fine, SPI lines are fine.
On my board, the analog input doesn't work at all. No sign of life on the SPI_MISO pin (which stays high), and more unexpectedly, no sign of life on P9_15 which is the chip select line for the ADC. The latter would explain the former.
Digging further, I find that this pin (GPIO1_16) has been set to pinmux mode 0 on the BBGW, but the exact same image running on the BBB sets it to mode 7. Mode 7 (GPIO) is correct; mode 0 is the gpmc_a0 signal. The neighbouring pins which also have GPMC functions are unaffected.
There are two other pins (pin 34 and pin 88, using the pinmux numbering) which also change from the BBB to the BBGW, but neither of these pins appears to go out to P8 or P9, so I don't know what they are doing. More to the point, I'm not yet sure where in the code it would be detecting this different hardware and setting the pins accordingly.
I don't see anything on the schematic of the BBGW that indicates why P9_15 would be used by anything else, so it's a bit of a mystery.
