nRF5340 I2S MCLK issue – unable to get 12.288 MHz MCLK for 48 kHz sampling
I am using the nRF5340 SoC and configuring the I2S peripheral as Master to achieve a 48 kHz audio sampling rate with an expected MCLK of 12.288 MHz (256 × 48 kHz).
With my current I2S configuration:
-
LRCLK is correctly measured at 48 kHz
-
SCLK is measured at 3.072 MHz
-
However, when I measure MCLK on the MCK pin, I only see ~100 kHz, which is not the expected value of 12.288 MHz
The I2S data clocks (LRCLK and SCLK) appear to be correct, but the MCLK output frequency is incorrect.
below are the i2s configurations
nrfx_i2s_config_t config; // Structure to hold I2S configuration settings
config.alignment = NRF_I2S_ALIGN_LEFT;
config.format = NRF_I2S_FORMAT_I2S;
config.mode = NRF_I2S_MODE_MASTER;
config.channels = NRF_I2S_CHANNELS_STEREO;
config.sample_width = NRF_I2S_SWIDTH_32BIT;
config.mck_setup = NRF_I2S_MCK_32MDIV5;
config.ratio = NRF_I2S_RATIO_256X;
config.clksrc = NRF_I2S_CLKSRC_ACLK;
config.enable_bypass = true;
config.mck_pin = NRF_I2S_PIN_NOT_CONNECTED; // Master clock pin not connected 12
config.lrck_pin = NRF_GPIO_PIN_MAP(0, 11); // NRF_I2S_PIN_NOT_CONNECTED; // Word clock pin not connected
config.sck_pin = NRF_GPIO_PIN_MAP(0, 8); // NRF_I2S_PIN_NOT_CONNECTED; // Bit clock pin not connected
config.sdout_pin = NRF_GPIO_PIN_MAP(0, 9); // NRF_I2S_PIN_NOT_CONNECTED; //NRF_GPIO_PIN_MAP(1,14); // Serial data output pin
config.sdin_pin = NRF_GPIO_PIN_MAP(0, 10); // Serial data input pin
config.irq_priority = 2;
