AN332
184
Confidential Rev. 0.2
There are two additional properties each for FM Transmitter and AM/FM/SW/LW Receiver associated with using
digital audio input/output. Note that digital audio is not supported in WB Receiver.
For FM Transmitter:
1. Property 0x0101: DIGITAL_INPUT_FORMAT
2. Property 0x0103: DIGITAL_INPUT_SAMPLE_RATE
For AM/FM/SW/LW Receiver:
1. Property 0x0102: DIGITAL_OUTPUT_FORMAT
2. Property 0x0104: DIGITAL_OUTPUT_SAMPLE_RATE
The procedure for using a digital audio is as follow:
1. When the device is powered up, the default value for DIGITAL_INPUT_SAMPLE_RATE or
DIGITAL_OUTPUT_SAMPLE_RATE is 0 (disable digital audio in/out).
2. User then must supply DCLK and DFS prior to setting the DIGITAL_INPUT_SAMPLE_RATE or
DIGITAL_OUTPUT_SAMPLE_RATE property.
3. This procedure can be applied anytime after the chip is powered up.
4. User may also change or disable DCLK/DFS during operation. Prior to changing or disabling DCLK/DFS, user
has to set the DIGITAL_INPUT_SAMPLE_RATE or DIGITAL_OUTPUT_SAMPLE_RATE property to 0. After
changing or re-enabling DCLK/DFS, user then can set the sample rate property again.
5. The property DIGITAL_INPUT_FORMAT and DIGITAL_OUTPUT_FORMAT does not have a condition, thus it
can be set anywhere after power up.
Notes:
1.
Failure to provide DCLK and DFS prior to setting the sample rate property may cause the chip to go into an unknown
state and user must reset the chip.
2.
The DIGITAL_INPUT_SAMPLE_RATE or DIGITAL_OUTPUT_SAMPLE_RATE is the audio sampling rate (DFS rate)
and is valid between 32kHz and 48kHz.
The following table is a programming example of how to use digital audio.
Table 40. Digital Audio Programming Example
Action
Data
Description
Action: POWER UP CHIP (look at respective programming example of
power up in digital mode).
Action: User can send other commands or properties here.
Action: Supply DCLK and DFS.
CMD
ARG1
ARG2 (PROP)
ARG3 (PROP)
ARG4 (PROPD)
ARG5 (PROPD)
STATUS
0x12
0x00
0x01
0x03 or 0x04
0xBB
0x80
→
0x80
SET_PROPERTY
DIGITAL_INPUT_SAMPLE_RATE or
DIGITAL_OUTPUT_SAMPLE_RATE
Sample rate = 0xBB80 = 48000Hz
Reply Status. Clear-to-send high.