ADC Entropy Source Plugin#

mbedtls_entropy_adc_init#

void mbedtls_entropy_adc_init (mbedtls_entropy_adc_context *ctx)

Initialize an ADC entropy context.

This function will initialize an ADC entropy context. This function will not initialize the ADC hardware instance as an entropy source. The user must call mbedtls_entropy_adc_set_instance in order to initialize the ADC hardware to entropy source mode.

mbedtls_entropy_adc_set_instance#

int mbedtls_entropy_adc_set_instance (mbedtls_entropy_adc_context *ctx, unsigned int adc_inst)

Set and initialize an ADC hardware instance.

This function will initialize an ADC hardware instance as an entropy source by starting the ADC clock and initializing registers to prepare collecting entropy in single sample mode. This function assumes that the ADC clock mode is set to SYNC, i.e. the HFPERCLK generates the ADC_CLK.

Returns

• 0 for success or MBEDTLS_ERR_ENTROPY_SOURCE_FAILED if adc_inst is invalid.

mbedtls_entropy_adc_free#

void mbedtls_entropy_adc_free (mbedtls_entropy_adc_context *ctx)

Free ADC entropy context.

This function will reset the ADC peripheral and stop the ADC clock. If more than one ENTROPY_ADC contexts are instantiated the user should be aware that one call to mbedtls_entropy_adc_free with any of the ADC entropy contexts will disable the ADC and effectively disable all other calls in the ADC entropy API, except mbedtls_entropy_adc_init and mbedtls_entropy_adc_set_instance which will enable the ADC again. Normally the application will need only one ADC entropy context.

mbedtls_entropy_adc_poll#

int mbedtls_entropy_adc_poll (mbedtls_entropy_adc_context *ctx, unsigned char *output, size_t len, size_t *olen)

Poll for entropy data.

This function will return entropy data from the ADC and place it into the output buffer. The len parameter tells this function the maximum number of bytes to read.

Note that the number of bytes read from the ADC might differ from the number of bytes requested.

The return value should be used to see if the operation was successful of if an error was encountered while reading the ADC. The content of the olen parameter can be used to check how many bytes were actually read.

Returns

• Always 0 for success.