Hello FC community, Today I have received and set up the Rigol DS1054Z oscilloscope I bought, and I have performed the experiment I've been wanting to do for a long time: I put the scope probe on the MCSI_CLK and MCSI_FSYNCH Calypso signals brought out to header pins on the FCDEV3B to see if the Calypso DSP puts the interface into clock master or clock slave mode. The results are:
* When the voice path is not in one of the "Bluetooth" modes, e.g., after booting the standard Magnetite fw but before giving it any special commands, MCSI_CLK sits at a constant low, probably from the pull-down resistor on the board, i.e., it is probably configured as an input inside the chip at this time. * As soon as I issue an auw 0 2 command through fc-tmsh to switch the voice path into the "Bluetooth headset" mode, a 520 kHz clock appears on the MCSI_CLK line and an 8 kHz clock appears on MCSI_FSYNCH, i.e., the DSP code we are running (combination of the DSP ROM and the patches from TCS211 which are required for our TCS211-based production fw to work correctly) is putting MCSI into clock master mode once the interface is put into use. The next part to be determined experimentally is the format in which the Calypso DSP puts out the digital voice samples on this interface: is it the native 16-bit linear PCM format, or does the DSP convert them to A-law PCM or mu-law PCM or CVSD because the interface was meant for Bluetooth? I certainly hope that it is the native 16-bit linear PCM format, which would make MCSI strictly no worse than tapping into TI's internal interface between Calypso and Iota chips, but it needs to be confirmed experimentally before we can jump to any conclusions. The approach I am currently considering for further MCSI investigation (now that we know that only MCSI_RXD is an input to the Calypso and the other 3 signals are outputs) is to connect the MCSI signals from our FCDEV3B to the McBSP signals on a BeagleBoard-xM. The only hitch is that the OMAP (BeagleBoard processor) signals are 1.8V and not tolerant of Calypso's 2.8V levels, thus a level shifter will be needed, and we may need to make a custom PCB with these level shifters (both ways) on it. I will think about it more after I get some sleep. Hasta la Victoria, Siempre, Mychaela aka The Mother _______________________________________________ Community mailing list [email protected] https://www.freecalypso.org/mailman/listinfo/community
