User Guide

NEM-2

System Module and User Interface CCS Technical Documentation

Audio routing and conditioning

The analog audio sources FM radio and line in are mixed and level conditioned in a pas-

sive stereo mixer and then fed through the Audio Codec RLINEIN and LLINEIN. The GSM

downlink from the UEMK HFOUT for headset is added by the codec mono analog input

(MICIN).

Source selection is controlled by software using the mute function for GSM downlink

and power on/off for FM radio. FM radio is powered off when not in use for power sav-

ing. The TMUTE pin of the TEA5767 is not used. Disabling the output stage of the UEMK

mutes the GSM downlink signal. Line in signal is the master signal and can’t be muted.

Line in connection is detected via software and switches the FM radio off.

Line in detection is done via sense line from the 2.5mm jack connector to UPP GENIO13.

The amplification and routing of the analog audio sources and outputs of the audio

codec is done via the control interface (SDIN, SCLK, CS, MODE) and the digital audio

interface (LRCIN, DIN, LROUT, DOUT, BCLK) from the DA250.

Audio signal routing is done by software. The hardware concept is fixed wired. The soft-

ware manages the sources/ inputs and the outputs that will be connected for the used

path. Level and volume control, the equalizing for the selected path and the user wishes

of tone settings or adjustment are also controlled by software. The different use cases

are described in the document Hitchhiker use cases.

When recording from FM radio or line in the signal can be monitored via headset. A

phone call during recording is possible with headset. The recorded signal is mixed into

the GSM downlink by the audio codec with lower level for background monitoring. The

GSM downlink has no influence to the recorded audio signal.

The block diagram of the audio part and the AIC23B audio codec can be found in the fol-

lowing picture.