User's Manual

L720 EVB User Manual

Note: L720 has only one main antenna interface, and the user can only use ANT_MAIN as

the antenna interface when it is actually used.

5.8 Audio interface（TBD）

The L720 module supports 1-channel PCM channel, which can also be reused as I2S signal. When

using, switch S2 and S3 are needed to cooperate. The switch S2 is a software and hardware switch.

When switching S2 to the top, the software can pull GPIO25 high level to make the power supply

and crystal vibration of CODEC; When switching S2 to the bottom, the hardware automatically

enables the power and crystal oscillator of CODEC. The switch S3 is the selection switch of

CODEC. When switching S3 to the top, CODEC uses MAX9867ETJ+ chip. When using the

MAX9867ETJ+ chip, the sound comes from the earphone, the Chinese standard earphone needs to

be plugged in. Switch S3 to the bottom, the CODEC chip is NUA8814. At this time, the sound

comes from the SPK end, and 8 ohm horn can be welded to the SPK end. Toggle switch as shown

in the figure below:

Figure5-8: CODEC SWITCH S2 S3

The default audio solution on EVB development board is NAU8814, so the external audio channel

is also developed based on NAU8814. The general block diagram is as follows: