Espressif ESP32 Technical Reference Manual page 319

12 I2S Controller (I2S)
I2S_TX_FIFO_MOD[2.0] and I2S_TX_CHAN_MOD[2:0]. I2S_TX_FIFO_MOD[2.0] determines whether the data
are 16-bit or 32-bit, as shown in Table 12-2, while I2S_TX_CHAN_MOD[2:0] determines the format of the data-
to-be-sent, as shown in Table 12-3.
I2S_TX_CHAN_MOD[2:0]
0
1
2
3
4
REG[31:0] is the value of register I2S_CONF_SINGLE_DATA_REG[31:0].
The output of the third stage is determined by the mode of the I2S and I2S_TX_BITS_MOD[5:0] bits of register
I2S_SAMPLE_RATE_CONF_REG.
12.4.5 Receiving Data
The data-receive phase of the ESP32 I2S module consists of another three stages:
• The input serial-bit stream is transformed into a 64-bit parallel-data stream in I2S mode. In LCD mode, the
input parallel-data stream will be extended to a 64-bit parallel-data stream.
• Received data are written into FIFO.
• Data are read from FIFO by CPU/DMA and written into the internal memory.
At the first stage of receiving data, the received-data stream is expanded to a zero-padded parallel-data stream
with 32 high-order bits and 32 low-order bits, according to the level of the I2SnI_WS_out (or I2SnI_WS_in)
signal. The I2S_RX_MSB_RIGHT bit of register I2S_CONF_REG is used to determine how the data are to be
expanded.
Espressif Systems
Table 12-3. Send Channel Mode
Description
Dual channel mode
Mono mode
When I2S_TX_MSB_RIGHT equals 0, the left-channel data are "holding"
their values and the right-channel data change into the left-channel data.
When I2S_TX_MSB_RIGHT equals 1, the right-channel data are "holding"
their values and the left-channel data change into the right-channel data.
Mono mode
When I2S_TX_MSB_RIGHT equals 0, the right-channel data are "hold-
ing" their values and the left-channel data change into the right-channel
data.
When I2S_TX_MSB_RIGHT equals 1, the left-channel data are "holding"
their values and the right-channel data change into the left-channel data.
Mono mode
When I2S_TX_MSB_RIGHT equals 0, the left-channel data are constants
in the range of REG[31:0].
When I2S_TX_MSB_RIGHT equals 1, the right-channel data are constants
in the range of REG[31:0].
Mono mode
When I2S_TX_MSB_RIGHT equals 0, the right-channel data are con-
stants in the range of REG[31:0].
When I2S_TX_MSB_RIGHT equals 1, the left-channel data are constants
in the range of REG[31:0].
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ESP32 TRM (Version 5.2)