AN1335 - APPLICATION NOTE

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8.2.1 - ADC Software Driver Considerations

The handling of bit XADCMUX shall be done preferably by a unique piece of software.

If ADC automatic scan is used (with or without PECC) to fill-up a table of conversion channels, it shall be

the software driver responsibility to handle this bit and generate the correct address to write to this table).

8.3 - XTimer

Xtimer, which allows to activate an external pin, which in the end can trigger an ADC conversion request

can also be fully supported by the emulator.

Allthough it is fully supported, some care is necessary :

The conversion-injection-request will be triggered without knowing the value of bit XADCMUX.

Practically, in engine control application, this bit may change dynamically and ensuring a predefined value

during injection request may be difficult.

As a result, it is advised to duplicate to 2 analog channels the analog signal to compare on injection

request.

Note:

It is better to allocate P5.15 and P10.15 to the channel to convert on injection request : this allow

to optimise the number of channels to scan during the auto-scan of the ADC channels.

8.3.1 - Manual Injection Conversion Request

Injection conversions can be initiated by software rather than Xtimer. This feature is already existing on

ST10 and requires to write to bit INJ_REQ in ADCON register.

8.3.2 - Proposal of ADC Driver When Converting All Channels Regularly

This proposal is showing how to configure ST10F280 when scanning regularly all channels and storing

conversion results with PECC :

ADC scan start routine : unchanged

PECC : end-of-count interrupt routine :

– Must be changed to distinguish between 1st half of scan and second half of scan (new variable needed).

– To summarize :

– Check bit XADCMUX,

– If 1st half (assume XADCMUX=0), change bit XADCMUX, start another scan,

– If 2nd half : re-init PECC for xx channels (1 to 16), change bit XADCMUX.

– Here, we assume that ADC scan are initiated by another routine (either timer based, ...).

ADC + PECC init routine : to allow more room for the table of conversion results.

8.3.3 - Example

The example hereafter illustrates how to generate of X_ADC_INJ output for the channel injection mode of

the A/D converter. It both describes the software and hardware configurations. XTIMER is used as a

counter that is clocked with XCLK divided by 8 and that counts from 0 (start value) to F (end value). It is

configured with "continue" and "reload start value" mode.