Channel Selection (Sqrx, Jsqrx) - ST STM32L4x6 Reference Manual

Analog-to-digital converters (ADC)
16.3.11

Channel selection (SQRx, JSQRx)

There are up to 19 multiplexed channels per ADC:
•
5 fast analog inputs coming from GPIO pads (ADC_IN1..5)
•
Up to 10 slow analog inputs coming from GPIO pads (ADC_IN6..15). Depending on the
products, not all of them are available on GPIO pads.
•
The ADCs are connected to 5 internal analog inputs:
–
–
–
–
–
Note: To convert one of the internal analog channels, the corresponding analog sources must first
be enabled by programming bits VREFEN, CH17_SEL or CH18_SEL in the ADCx_CCR
registers.
Caution: Before any conversion of an input channel coming from GPIO pads, it is necessary to
configure the corresponding GPIOx_ASCR register in the GPIO, in addition to the I/O
configuration in analog mode.
It is possible to organize the conversions in two groups: regular and injected. A group
consists of a sequence of conversions that can be done on any channel and in any order.
For instance, it is possible to implement the conversion sequence in the following order:
ADC_IN3, ADC_IN8, ADC_IN2, ADC_IN2, ADC_IN0, ADC_IN2, ADC_IN2, ADC_IN15.
•
A regular group is composed of up to 16 conversions. The regular channels and their
order in the conversion sequence must be selected in the ADCx_SQR registers. The
total number of conversions in the regular group must be written in the L[3:0] bits in the
ADCx_SQR1 register.
•
An injected group is composed of up to 4 conversions. The injected channels and
their order in the conversion sequence must be selected in the ADCx_JSQR register.
The total number of conversions in the injected group must be written in the L[1:0] bits
in the ADCx_JSQR register.
ADCx_SQR registers must not be modified while regular conversions can occur. For this,
the ADC regular conversions must be first stopped by writing ADSTP=1 (refer to
Section 16.3.17: Stopping an ongoing conversion (ADSTP,
It is possible to modify the ADCx_JSQR registers on-the-fly while injected conversions are
occurring. Refer to
16.3.12 Channel-wise programmable sampling time (SMPR1, SMPR2)
Before starting a conversion, the ADC must establish a direct connection between the
voltage source under measurement and the embedded sampling capacitor of the ADC. This
sampling time must be enough for the input voltage source to charge the embedded
capacitor to the input voltage level.
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the internal reference voltage (V
the internal temperature sensor (V
ADC3_IN17.
the V monitoring channel (V
BAT
ADC3_IN18.
the DAC1 internal channel is connected to ADC2_IN17 and ADC3_IN14.
the DAC2 internal channel is connected to ADC2_IN18 and ADC3_IN15.
Section 16.3.21: Queue of context for injected conversions
DocID024597 Rev 3
) is connected to ADC1_IN0.
REFINT
) is connected to ADC1_IN17 and
TS
/3) is connected to ADC1_IN18 and
BAT
JADSTP)).
RM0351