Download BTM510/511 Multimedia Module User Guide

BTM510/511 User Guide
®
Bluetooth Multimedia Module
(S415=0)
Figure 2-31: BTM51x ADC Analogue Amplifier Block Diagram
2.8.2 Digital Audio Interface
Bluecore BC05 allows audio streams to be routed to a digital audio interface instead of the internal
codec. These sections describe details of the digital audio interface.
2.8.2.1
I2S – Inter Integrated Circuit Sound
I2S is a digital interface to transmit stereo audio data between integrated circuits (IC) in embedded
systems. It connects an external audio CODEC or a wave file player/recorder to a BTM module. As most
of audio media is available digitally these days, there is no need to convert audio to analogue and then
back to digital on the BTM5xx module.
Provided a digital medium is played over A2DP, with a BTM5xx as A2DP source, then a D/A and
subsequent A/D conversion between the digital medium and the module (A2DP source) would lose
signal quality due to non-optimal settings of DAC / ADC gains and noise picked up in the analogue
path.
These issues can be eliminated by using the digital I2S interface rather than the analogue audio input.
An I2S interface consists of at least 3 signals: bus clock (SCK), word select (WS, left/right channel) and
serial data (SD_IN / SD_OUT). On a BTM5xx module, there are separate data lines for in input and
output, for a total of four I2S signals. I2S signals are mapped to the PCM pins of a BTM51x as outlined
in Table 2-70.
When connecting two devices via I2S, one must be the I2S master and the other must be the I2S slave.
The I2S master provides SCK and WS signals (output) and the I2S slave synchronises to these signals (WS
and SCK = input). S registers S314 (A2DP) and S315 (SCO) select the I2S role for a BTM51x (I2S master /
I2S slave).
Table 2-70: BTM51x I2S signal pin mapping
I2S Signal
name
BTM51x Signal
name
BTM51x
module pin no.
Mini devkit PCM
header (J5)
SD_IN
PCM_IN
3
5
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I2S Serial data in
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