topic Analog to Digitial Convertor Multiple channel using MUX in MQX Software Solutions

Analog to Digitial Convertor Multiple channel using MUX

LANCO_M4 — Sat, 25 Feb 2012 20:03:06 GMT

We are attempting to read multiple channels, more than 2, using one of the A2D convertors on a K70 with MQX3.8. I have seen in another post that stated when using MQX this may require us to perform successive Open and Close channel operations. It doesn’t appear that MQX on the K70 supports the ability to Open more than two single ended channels or one differential channel at a time per A2D convertor.

Can someone confirm this?

Re: Analog to Digitial Convertor Multiple channel using MUX

c0170 — Sun, 26 Feb 2012 02:59:53 GMT

Hi Lanco_m4,

What you stated it's true for K70.

Regards,

MartinK

Re: Analog to Digitial Convertor Multiple channel using MUX

DavidS — Mon, 27 Feb 2012 22:20:41 GMT

Hi Lanco_m4,

You are correct for the Kinetis SAR ADC module. Each module has two sample registers that can be configured to trigger simultaneously or delayed from one another using the PDB (Peripheral Delayed Block).

You can use a "static" method setup the ADC modules to sample different pins but this limits you to the two samples per ADC module.

If you use the other features of Kinetis like the eDMA and the various methods that allow the peripheral to trigger one another, then a "dynamic" method can be used:

ex: PIT timer used to trigger the eDMA to transfer ADC command to trigger the ADC sample. When the ADC sample completes, it can trigger the eDMA to get the result from ADC module and move to SRAM.

To summaries, if you have 2 or less samples per ADC module you want then a static approach may work. If you have more than 2 samples per ADC module then you need to use a dynamic approach (fast approach) that allows the hardware to reconfigure your ADC for samples or use dynamic code to setup ADC modules (slower approach).

Hope this helps.

Regards,

David