I2S communication format unclear (IDFGH-2913)

[callalilychen]

According to the reference manual of esp32, for I2s, 3 Audio Standards are supported, but I am not sure, how to configure the three standards using the esp-idf. Because in the i2s_types.h, 6 communication formats are defined:

esp-idf/components/soc/include/hal/i2s_types.h

Lines 64 to 71 in 0ae960f

	typedef enum {
	I2S_COMM_FORMAT_I2S = 0x01, /*!< I2S communication format I2S*/
	I2S_COMM_FORMAT_I2S_MSB = 0x02, /*!< I2S format MSB*/
	I2S_COMM_FORMAT_I2S_LSB = 0x04, /*!< I2S format LSB*/
	I2S_COMM_FORMAT_PCM = 0x08, /*!< I2S communication format PCM*/
	I2S_COMM_FORMAT_PCM_SHORT = 0x10, /*!< PCM Short*/
	I2S_COMM_FORMAT_PCM_LONG = 0x20, /*!< PCM Long*/
	} i2s_comm_format_t;

I can not find further information about these enums entries, so I read the code. But I can not understand, what is the difference between these configs:

.communication_format = I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB, 

or

.communication_format = I2S_COMM_FORMAT_I2S, 

To receive/send audio in MSB Alignment Standard, should I configure the communication format like this:

.communication_format = I2S_COMM_FORMAT_I2S_LSB, 

Can somebody explain it? It will be very nice to also improve the documentation for I2S https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/i2s.html#functional-overview

[koobest]

Hi, @callalilychen
Thank you for reporting this issue. If MSB-aligned communication format is required, it should be configured as "I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_LSB" and we will improve the documentation.

thanks !!

[Alvin1Zhang]

@callalilychen Thanks for reporting, we have a fix which is now under internal reviewing, will update once it is available on GitHub. Thanks.