2021 Microchip Technology Inc. DS00003118C-Page 36
AN3118
connected sink device and follow step 5 and
step 6 to connect with a second sink device.
9. Now, power-on the first sink device to connect it
with the BM83.
10. Connect an audio source to Aux-in/I
2
S and play
music to stream out the music through both con-
nected sink devices.
11. Double press the Vol- button to Toggle mode
(Tx/Rx)
12. Short press the Rev button to toggle the Audio
Source
13. Short press the Fwd button to toggle sampling
frequency
3.4 Audio Input to BM83 Source
The BM83 Source mode takes both I
2
S and Aux-in as
inputs. Plug in the Aux-in cable to the BM83 EVB and
connect other end to the Aux-in input source (for
example, a PC). Audio will be heard on both connected
sink devices.
For I
2
S input, make the connection between the I
2
S
input device and the BM83 as shown in the following
figure.
FIGURE 35: CONNECTION BETWEEN BM83 AND I
2
S DEVICE
Issue commands 44 2 1 and 13 01 00 to switch the
audio source to I
2
S in Host mode. To switch the audio
source back to Aux-in, issue commands 44 2 0 and
13 01 01. In Embedded mode, GPIO toggling is
needed to switch the input source between I
2
S and
Aux-in (see Section 3.6, Audio Input).
3.5 A2DP Source Mode
By programming the BM83 with AT enabled firmware,
we can use the BM83 as an A2DP source or sink
device. The BM83 can work either as an A2DP source
or sink device, but cannot work as source and sink at
the same time. By flipping a switch connected to GPIO
(configured via Config_GUI_Tool) in Embedded mode,
or by sending Change_APP_Mode(0x44 03 00/01)
UART command in Host mode, the BM83 can work as
a source or sink device. The BM83 source can connect
to two sink devices at the same time.
Following are the UART commands to facilitate the
BM83 transmitter:
• Device_Discovery(0x44 0x00)
• Discovery_Cancel(0x44 0x01)
• Change_Audio_Source(0x44 0x02)
• Change_APP_Mode(0x44 0x03)
• Read_App_Mode(0x44 0x04)
• Read_Audio_Input_Source (0x44 0x05)
• Change_Audio_In_Sampling_Rate_Cmd
(0x44 0x06)
• Read_Audio_In_Sampling_Rate_Cmd
(0x44,0x07)
• Block_Unblock_A2DP_STream(0x44 0x8)
Following are the UART events for the audio
transmitter:
• Discovery_Response (0x5A 0x00)
• Discovery_Complete (0x5A 0x01)
• Audio_Input_Source (0x5A 0x02)
• Audio_Application_Mode (0x5A 0x03)
• Audio-In Sampling Rate(0x5A,0x04)
BM83 I
2
S Device
RFS
LRCLK
SCLK
BCLK
DR0
DT
GND
GND
Note: By default, BM83 AT firmware is in A2DP
source mode when configured in Host
mode and depending on the GPIO state
(1: source, 0: sink) in Embedded mode.
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