Hello,

I try to built an DMA channel from a ADC SAR to one filter channel it works only for 8 bit.

Kann anyone tell me how to handle 12 bit data stream?

Or may be i don´t now how to read the memory of holding register,

I took the comment " Filter_Read16(Filter_CHANNEL_B)" .

Can somebody help me

Thanks a lot.

Dick22

Hi Dick22,

If you are using SAR ADC differential configuration, the output will be in 2's compliment form.

So, the 12 bit output should be left aligned (left shift by 4 bits) and fed into the Staging Registers (High Byte and Middle Byte).

You can do this by creating a Custom Component using UDB for shifting.

HI dasq

thank you a lot for this information. Yes I took a SAR ADC but is it not possible in the single mode

I´m sorry but  I don´t know how to create a UDB for this shifting. Will a UDB need CPU resources because I need a datarate with 1000000 samples per second.

Hi Dick22,

Using UDB for shifting will not use CPU resource once the initializations are done for it.

However I feel that using UDB will have a lot of DMA channels being consumed, as the SAR ADC value has to be transmitted to UDB via DMA, the value has to be  shifted, and then has to be transmitted again using another DMA channel.

This might be a resource consuming solution.

However a workaround for the sign-bit extension in SAR ADC Component will soon be brought about.