65.6.13.2 Averaging Function versus Trigger Events

The samples can be defined in different ways for the averaging function depending on the configuration of ADC_EMR.ASTE and ADC_MR.USEQ

When USEQ = 0, there are two possible ways to generate the averaging through the trigger event. If ADC_EMR.ASTE = 0, every trigger event generates one sample for each enabled channel, as described in the following figure. Therefore, four trigger events are required to obtain the result of averaging if OSR = 1.

Figure 65-11. Digital Averaging Function Waveforms Over Multiple Trigger Events

If ADC_EMR.ASTE = 1 and ADC_MR.USEQ = 0, the sequence to be converted, defined in ADC_CHSR, is automatically repeated n times (where n corresponds to the oversampling ratio defined in the ADC_EMR.OSR field). As a result, only one trigger is required to obtain the result of the averaging function as described in the following figure.

Figure 65-12. Digital Averaging Function Waveforms on a Single Trigger Event

When USEQ = 1, the user can define the channel sequence to be converted by configuring ADC_SEQRx and ADC_CHER so that channels are not interleaved during the averaging period. Under these conditions, a sample is defined for each end of conversion as described in the figure below.

When USEQ = 1 and ASTE = 1, OSR can be only configured to 1. Up to three channels can be converted in this mode. The averaging result will be placed in the corresponding ADC_CDRx and in ADC_LCDR for each trigger event. The ADC real sample rate remains the maximum ADC sample rate divided by 4.

It is important that the user sequence follows a specific pattern. The user sequence must be programmed in such a way that it generates a stream of conversion, where a same channel is successively converted.

Table 65-4. Example Sequence Configurations (USEQ = 1, ASTE = 1, OSR = 1)
Register Number of Channels Non-interleaved Averaging - Register Value
1 (e.g., CH0) 2 (e.g., CH0, CH1) 3 (e.g., CH0, CH1, CH2)
ADC_CHSR 0x0000_000F 0x0000_00FF 0x0000_0FFF
ADC_SEQR1 0x0000_0000 0x1111_0000 0x1111_0000
ADC_SEQR2 0x0000_0000 0x0000_0000 0x0000_2222
Figure 65-13. Digital Averaging Function Waveforms on a Single Trigger Event, Non-interleaved