Chapter 7
On-board peripherals
This section describes how the on-board peripheral devices of the board are connected to the IMXRT685 and relevant
configuration options. For details of these devices, please refer to the individual device datasheets. For further details on the
circuit, refer to the board schematics.
7.1 Audio Codec
The MIMXRT685-EVK board incorporates a Cirrus Logic WM8904 audio codec. This codec has both I
2
C (for control) and I
2
S
(for data) interfaces. The I
2
C interface of the codec is routed to Port 2 of the IMXRT685, with the same connection for the audio
amplifiers and the I3C header on the board. The Codec has an address of
0b0011010
.
The I
2
S interface of the codec is routed to Port 0 of the IMXRT685, the same connection as used for the audio amplifiers.
Depending on the voltage of
VDDIO_1
, the audio Codec is designed to operate with two options, with level shifter (U35 and U36)
and without level shifter.
Table 6. Audio Codec port connections
Circuit reference
Port
I2C SDA
P2_30
I2C SCL
P2_29
I2S BLCK
P0_7
I2S DAI
P0_9
I2S DAO
P0_23
I2S WS
P0_8
CODEC MCLK
P1_10
There are three jumpers (JP6, JP7 and JP8) to select IMXRT685 I2S connections lines between Codec and amplifier. To select
the Codec, jumpers must be (1-2). See schematic for further information.
Line input (J3) and line output (J4) ¼” stereo jack sockets provide analog I/O connections to the Codec. See schematic for further
information.
7.2 Audio digital amplifiers
A pair of audio amplifiers are included on the MIMXRT685-EVK. Select the external supply between JP24 5V Jack (JP11, 2-3)
or J6 USB (JP11, 1-2). The I
2
C interface of the amplifiers is routed to Port 2 of the IMXRT685, the same connection as used for
the codec and the I3C header on the board.
The I
2
S interface of the amplifiers is routed to Port 0 of the IMXRT685, with the same connection for the codec.
Depending on the voltage of
SW2_OUT
, the audio AMP operates at either 1.8 V or 3.3 V. A level shifter (U34) is added.
Table 7. Digital audio amplifier port connections
Circuit reference
Port
I2C SDA
P2_30
I2C SCL
P2_29
Table continues on the next page...
NXP Semiconductors
i.MX RT685 Evaluation Board, Rev. 0, March 20 2020
User's Guide
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