ADC triggered by FMT

[mkrug]

Hi,

I am using a K60 TWR system and want to setup a timer that triggers with a certain period the ADC1 converter (used by the onboard potentiometer). So I setup the Trigger of the ADC as follows:

Trigger: enabled

Trigger signal list: 1

Trigger signal 0: Enabled

Trigger input: Flex_timer_0

Trigger type: internal

Source component: TU1 (thats the name of my timer)

Trigger activate state: Rising edge

The FMT0 is configured as:

Component name: TU1

Module name: FTM0

Counter: FTM0_CNT

Counter direction: Up

Counter frequency: 256Hz

Period: 1sec

My source code looks like:

  ADC1_Data = AD1_Init(NULL);
  SampleGroup[0].ChannelIdx = 0U;
  Error = AD1_CreateSampleGroup(ADC1_Data, (LDD_ADC_TSample *)SampleGroup, SAMPLE_GROUP_SIZE);
  Error = AD1_StartLoopTriggeredMeasurement(ADC1_Data);

So I thought the ADC should convert every second. However it does not - what did I wrong?

BTW - how can I synchronize a PDB Block to an overrun/restart of a FMT.

Best Regards

Markus

[ProcessorExpert · Accepted solution]

Hello,

I think that I have answered your first question within this thread:

https://community.freescale.com/thread/117612

You must additionaly write to the EXTTRIG register in user code.

best regards
Vojtech Filip
Processor Expert Support Team

[mkrug]

Hi,

I found a solution to use the FMT to trigger an ADC. Attached you find a example project that works on the K60F120 TWR Board. The example uses the ADC_LDD and Init_FMT components. I used them because the ADC_LDD gives you access to the different methods and Init_FMT allows you to setup a FMT modul to generate the hardware triggers.

What is interesting to note:

The ADC that is triggered by a FMT can only convert 1 channel. I tried to setup another to add another ADC_LDD for the same ADC converter - this experiment fails. So you can just convert one channel of an ADC by a FMT component.

Using a PDB is a little bit better because you can setup two triggers for one ADC converter. However does one have an idea what to do to convert more then two channels triggered by a onchip component?

Best Regards

Markus

[ProcessorExpert]

Hi,

Regarding the triggering with FTM - yes, this is a limitation of the hardware, on K60 only one trigger from FTM is available.

For two triggers, the PDB can be used.

If you need more channels than 2 to be measured, you need to change the channel after each conversion within the OnMeasurementComplete event code (using SelectSampleGroup method, see the Typical usage help page for the ADC_LDD component).

Another possibility would be to use DMA for both configuring the channel and reading the result. However this is not a technique supported by the ADC_LDD component and the code is highly platform specific for the K60. I attach an example measuring multiple channels using PEx peripheral initialization components.

best regards
Petr Hradsky
Processor Expert Support Team