DocID023897 Rev 1

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Independent modes

2.2.4

Using the ADC in injected conversion

Injected channel configuration

1.

Configure the sequence length, the order of channels to be converted, the external

hardware trigger and the edge of this trigger, by configuring the ADC_JSQR registers.

2.

Configure the next context (if the queue of context will be used). Note that each write

access to the ADC_JSQR register is considered as a new context.

3.

Configure the sampling time for each channel to be configured, by writing to the

ADC_SMPRX registers.

4.

Select the JSQR mode by writing to the JQM bit in the ADC_CFGR register.

5.

Set the JAUTO bit if the injected sequence should be started after the regular channels.

6.

Configure the ADC resolution by writing to the RES bit in the ADC_CFGR register.

ADC start conversion

•

Software-injected ADC conversion is started immediately after the JADSTART bit is

set.

•

Hardware-injected conversion is started after the JADSTART bit is set, and at the next

active edge of the selected injected hardware trigger.

•

If JAUTO=1, both the regular and injected conversion channels use the ADSTART bit

to start the regular conversions, followed by the auto-injected conversions. This means

that JADSTART must be kept cleared.

ADC read conversion data

At the end of each injected conversion channel (when the JEOC event occurs), the

converted data result is stored in the corresponding 16-bit wide ADC_JDRx data register.

To read the converted data, both the JEOC flag/interrupt and the JEOS flag/interrupt can be

used to access the corresponding register.

2.2.5

Application examples

The injected conversion mode can be used to synchronize the conversion of channels to an

event. It is interesting in motor control applications where transistor switching generates

noise that impacts ADC measurements and results in wrong conversions. Using a timer, the

injected conversion mode can thus be implemented to delay the ADC measurements until

after the transistor switching.

The queue of context is used to synchronize the conversion of channels to an event, each

context uses a specific external trigger to convert a specific sequence of injected channels.

A typical example of application of the Queue of context is the dual motor control.