ADC problem

benelghali — Thu, 23 Jul 2015 09:16:29 GMT

Hi everyone,

I'm working with kinetis KV31F256 and i want to convert 7 analog channels using ADC modules the problem that i want the whole 7 conversions to start after ADC is triggered by a PDB trigger which is in his turn synchronised by FTM0 initialization trigger delayed by PDB . So the problem is that i don't want the 7 conversion to start one by one every PDB trigger i want a single PDB trigger to start the whole 7 conversions periodically.

Can someone help me please.

Thanks.

Re: ADC problem

xiangjun_rong — Thu, 23 Jul 2015 10:16:18 GMT

Hi,Bilel,

You use FTM module to trigger PDB and PDB trigger ADC after a programmable delay. From your description, you want to sample 7 channels for one FTM triggering event, I think it is impossible.

I suppose that once FTM triggering event can sample at most 4 ADC channels. This is the solution, for KV31, there are two ADC modules:ADC0 and ADC1 module, one PDB module. each ADC module supports Ping-Pong mode, for example, for ADC0 module, there are two ADC Status and Control Registers:ADC0_SC1A and ADC0_SC1B. The ADC0_SC1A can specifies one ADC0 analog channel, the ADC0_SC1B can specifies another ADC0 channels. The ADC1 module has two ADC Status and Control Registers:ADC1_SC1A and ADC1_SC1B.

The PDBCH0DLY0 can trigger the analog channel specified by ADC0_SC1A, the PDBCH0DLY1 can trigger the analog channel specified by ADC0_SC1B. The PDBCH1DLY0 can trigger the analog channel specified by ADC1_SC1A, the PDBCH1DLY1 can trigger the analog channel specified by ADC1_SC1B. It is required that the time difference between PDBCH0DLY1 and PDBCH0DLY0 should be greater than one ADC conversion time.

The PDB supports Back-to-Back ADC conversion, but the restriction is at most 4 ADC channels.

In conclusion, once FTM triggering event can trigger 4 ADC samples, two ADC0 channels, two ADC1 channels.

Hope it can help you.

XiangJun Rong

topic ADC problem in Kinetis Software Development Kit

ADC problem

Re: ADC problem