STM32W108HB datasheet(131/179 Pages) STMICROELECTRONICS

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STM32W108CB, STM32W108HB

Analog-to-digital converter

Doc ID 16252 Rev 2

131/179

9.1

Functional description

9.1.1

Setup and configuration

To use the ADC follow this procedure, described in more detail in the next sections:

●

Configure any GPIO pins to be used by the ADC in analog mode.

●

Configure the voltage reference (internal or external).

●

Set the offset and gain values.

●

Reset the ADC DMA, define the DMA buffer, and start the DMA in the proper transfer

mode.

●

If interrupts will be used, configure the primary ADC interrupt and specific mask bits.

●

Write the ADC configuration register to define the inputs, voltage range, sample time,

and start the conversions.

9.1.2

GPIO usage

A GPIO pin used by the ADC as an input or voltage reference must be configured in analog

mode by writing 0 to its 4-bit field in the proper GPIO_PnCFGH/L register. Note that a GPIO

pin in analog mode cannot be used for any digital functions, and software always reads it as

See Section 6: General-purpose input/outputs on page 46 for more information about how

to configure the GPIO pins.

9.1.3

Voltage reference

The ADC voltage reference (VREF), may be internally generated or externally sourced from

PB0. If internally generated, it may optionally be output on PB0.

To use an external reference, an ST system function must be called after reset and after

waking from deep sleep. PB0 must also be configured in analog mode using

GPIO_PBCFGH[3:0]. See the STM32W108 HAL documentation for more information on the

system functions required to use an external reference.

Table 15.

ADC GPIO pin usage

Analog Signal

GPIO

Configuration control

ADC0 input

PB5

GPIO_PBCFGH[7:4]

ADC1 input

PB6

GPIO_PBCFGH[11:8]

ADC2 input

PB7

GPIO_PBCFGH[15:12]

ADC3 input

PC1

GPIO_PCCFGH[7:4]

ADC4 input

PA4

GPIO_PACFGH[3:0]

ADC5 input

PA5

GPIO_PACFGH[7:4]

VREF input or output

PB0

GPIO_PBCFGH[3:0]

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