AN3137 datasheet(13/42 Pages) STMICROELECTRONICS

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AN3137

STM8L/STM8AL ADC usage/programming

Doc ID 16983 Rev 3

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STM8L/STM8AL ADC usage/programming

2.1

Sampling mode overview and usage

2.1.1

Single mode

In this mode, only one input channel must be selected in the ADC_SQRx registers (if more

channels are selected, the highest selected channel is measured). In addition, the DMAOFF

bit must be set in the ADC_SQR1 register (to disable DMA transfer). The input channel is

then converted and the ADC conversion stops (one simple conversion). The converted

value is stored into the ADC_DR data register. An interrupt (EOC) can be generated after

the end of conversion.

Note:

If the DMAOFF bit in the ADC_SQR1 register is reset (and if DMA is properly programmed)

the conversion is then performed in scan mode. Refer to Section 2.1.3: Scan mode.

2.1.2

Continuous mode

In this mode, the ADC does not stop after conversion but continues to the next channel in

the selected channel sequence. Conversions continue until the CONT bit and the ADON bits

are set and the converted values are transferred through the DMA to the RAM or EEPROM

memory buffer. As the EOC interrupt is generated only after the end of the conversion of the

selected channel sequence, the result of each channel conversion cannot be read from the

ADC_DR register.

To save the conversion of each channel in a memory (RAM or EEPROM), the DMA must be

used in peripheral to memory mode. If the CONT bit is reset during a conversion, the current

selected channel sequence conversions end with the last selected channel) and then the

ADC stops.

Note:

The CONT bit must not be set again during a conversion.

2.1.3

Scan mode

This mode works automatically in continuous mode. Refer to Section 2.1.2. It can also be

used in single mode by resetting the DMAOFF bit in the ADC_SQR1 register. Refer to

Section 2.1.1.

In scan mode, the selected channel sequence is taken into account (like in single mode) and

the selected channels are converted and transferred through DMA to memory (DMA should

be properly programmed).

If the single mode is selected, the ADC converts the selected channel sequence and it is

stopped after the last channel conversion. For the next selected channel sequence, a scan

conversion is necessary to restart the ADC.

An interrupt (EOC) can be generated after the end of the channel sequence conversion.

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