STM32 ADC Driver

Description

This driver supports the ADC devices available in some variants of the ST STM32 family of microprocessors.

Sample Size

The STM32 ADC on F1 series devices produces 12-bit samples. The F2 series devices can produce 12-, 10-, 8- or 6-bit samples though only 12-bit samples are currently supported by the STM32 ADC driver. Therefore this driver sets CYGNUM_IO_ADC_SAMPLE_SIZE to 12. This will cause the generic layer to define cyg_adc_sample_t as a 16-bit value.

Sample Rates

The ADC hardware is limited to a maximum of 2K samples per channel. Since up to 16 channels are sampled on a round-robin basis, this means that the total sample rate can be 16K samples per second.

Configuration

The option CYGNUM_DEVS_ADC_CORTEXM_STM32_CLOCK_DIV specifies the divider used to control the ADC system clock supplied by the RCC.

Each ADC device is controlled by a CDL component, CYGHWR_DEVS_ADC_CORTEXM_STM32_ADCX for each device X, which must be enabled to initialize the device. For STM32F1 devices only ADC devices 1 and 3 are available, since ADC2 shares GPIO lines and an interrupt with ADC1. For STM32F2 devices ADC devices 1, 2 and 3 are available.

For STM32F2 devices the selection of the DMA stream interrupt to be used for the specific ADC device is controlled by a CDL component, CYGHWR_DEVS_ADC_CORTEXM_STM32_ADCX_DMA for each device X, which must be configured to avoid clashes with other peripherals that may share the same DMA stream.

The option CYGNUM_DEVS_ADC_CORTEXM_STM32_ADCX_SAMPLE_TIME defines the duration over which each sample is taken for each channel, in microseconds.

The option CYGNUM_DEVS_ADC_CORTEXM_STM32_ADCX_DEFAULT_RATE defines the default sample rate for all channels attached to device X.

The option CYGNUM_DEVS_ADC_CORTEXM_STM32_ADCX_DMA_INT_PRI defines the DMA interrupt prioirity for this device. The default of 0x80 sets it in the middle of the prioirity range.

For each channel X in ADC device Y the CDL script provides the following configuration options: