Hardware description

Mounting instructions

RDK Audio Expansion Board

The RDK Audio Expansion Board has 4 plated mounting holes on its edges, and can be secured with 4 × M2.5 screws.

RDK Audio Expansion Board Adapter

The RDK Audio Expansion Board Adapter has 1 plated mounting hole, and can be secured with 1 × M2.5 screw, working with the 40PIN interface for firm mounting.

RDK Audio Expansion Board 4-Mic Array

The RDK Audio Expansion Board 4-Mic Array has 4 plated mounting holes, and can be secured with 4 × M3 screws.

RDK Audio Expansion Board 6-Mic Array

The RDK Audio Expansion Board 6-Mic Array has 3 plated mounting holes, and can be secured with 3 × M6 screws.

Note

• When mounting, use washers where appropriate and tighten the screws alternately to avoid cracking the PCB and damaging the product.
• If the mic array or speakers need to be installed into a sealed enclosure, design the sound-guiding structure yourself based on the actual situation to avoid affecting recording or playback quality.
• For the 3D model files, see Downloads.

Hardware interface description

Interface description

J1 left-channel amplifier interface

This interface connects a left-channel speaker and outputs left-channel audio through a differential signal. The differential polarity corresponds to the PCB silkscreen.

J2 right-channel amplifier interface

This interface connects a right-channel speaker and outputs right-channel audio through a differential signal. The differential polarity corresponds to the PCB silkscreen.

J4 debug UART

This interface is for internal debugging and should be avoided in daily use.

J7 USB interface

Used for flashing the expansion board firmware and for USB audio (UAC) functionality.

J10 audio digital interface

This interface breaks out the I2S and I2C signals to connect the RDK Audio Expansion Board Adapter or an RDK development board.

The connector PIN1 position matches the Mark point. The pinout is shown in the table below:

PIN	Name	Description
1	OUTCON_MCLK	MCLK signal of the audio Codec.
2	OUTCON_BCLK	BCLK signal of the audio Codec, used to synchronize serial audio data transmission.
3	OUTCON_WS	WS/LRCK signal of the audio Codec, used for I2S frame synchronization (left/right channel selection). Its frequency equals the audio sample rate.
4	OUTCON_SDIN	Connects to the DIN pin of the DAC. I2S serial data input, used for audio playback.
5	OUTCON_SDOUT1	Connects to the DOUT pin of the ADC. I2S serial data output, used for capturing microphone audio.
6	OUTCON_MCLK2	MCLK signal of the audio Codec.
7	OUTCON_BCLK2	BCLK signal of the audio Codec, used to synchronize serial audio data transmission.
8	OUTCON_WS2	WS/LRCK signal of the audio Codec, used for I2S frame synchronization (left/right channel selection). Its frequency equals the audio sample rate.
9	N/A
10	OUTCON_SDOUT2	Connects to the DOUT pin of the ADC. I2S serial data output, used for capturing microphone audio.
11	OUTCON_I2C_SDA	I2C data signal.
12	OUTCON_I2C_CLK	I2C clock signal.
13	GND
14	VCC_IN	Power supply, 4.5V-5.5V

Note

The audio interface selector switch can set the audio kit to single-channel or dual-channel I2S mode:

• In single-channel I2S mode, PIN 6-10 are invalid, and audio signals are transmitted full-duplex through PIN 1~5. However, when sampling and output are performed simultaneously, the sampling channel and output channel must be at the same sample rate.
• In dual-channel I2S mode, audio signals are output simplex through PIN 1~4 and sampled simplex through PIN 6-10. In this mode, the sampling channel and output channel can be at different sample rates.

J11 microphone array interface

This interface connects the RDK audio core board to the RDK 4-Mic or 6-Mic array.

The connector PIN1 position is near the Mark point (rightmost). The pinout is shown in the table below:

PIN	Name	Description
1	LED1+
2	LED1-
3	LED2+
4	LED2-
5	LED3+
6	LED3-
7	LED4+
8	LED4-
9	LED5+
10	LED5-
11	LED6+
12	LED6-
13	MIC1N_B	Mic differential signal output
14	MIC1P_B	Mic differential signal output
15	MICBIAS1_B	Mic bias voltage
16	AGND
17	MIC2P_B	Mic differential signal output
18	MIC2N_B	Mic differential signal output
19	MICBIAS2_B	Mic bias voltage
20	AGND
21	MIC1N_A	Mic differential signal output
22	MIC1P_A	Mic differential signal output
23	MICBIAS1_A	Mic bias voltage
24	AGND
25	MIC2P_A	Mic differential signal output
26	MIC2N_A	Mic differential signal output
27	MICBIAS2_A	Mic bias voltage
28	AGND
29	MIC3N_A	Mic differential signal output
30	MIC3P_A	Mic differential signal output
31	MICBIAS3_A	Mic bias voltage
32	AGND
33	MIC4P_A	Mic differential signal output
34	MIC4N_A	Mic differential signal output
35	MICBIAS4_A	Mic bias voltage
36	AGND

K1 RST button

This interface resets the audio kit state and should be avoided during normal use.

K2 LOAD button

This interface loads the debug mode of the audio board and should be avoided during normal use.

S1 audio interface selector switch

This interface is a 4-channel DIP switch used to select the audio interface, channel count, reference level, and other properties. The default state is as follows: all 4 channels are set to 0. Use tweezers to flip a channel up to set it to 1. The DIP switch state table is shown below:

PIN	Name	Description
1	USB/I2S selection	0: USB mode 1: I2S mode
2	I2S channel count selection	0: single-channel 1: dual-channel (for the audio interface of RDK S600)
3	I2S level selection	0: 1.8V 1: 3.3V
4	N/A

Connector models

Connector	Connector Model	Manufacturer
J1, J2	HC-1.25-2PWT	-
J10	X1251WRS-14HF-LPSW	XKB Connectivity