MPC5xxx中的主题 Re: dual conversion, ADC channel order question

dual conversion, ADC channel order question

duanemattern — Thu, 29 Dec 2016 22:34:54 GMT

I'm using a TRK-MPC5604P kit and I'm following the MPC5643L "PWM triggered measurement concept" tech note that has been posted in this forum, (I'm using the DMA code as provide). I've changed it to use dual conversion mode (both ADC0 & 1), and I'm getting data, using a PWM trigger of about 1.28ms for testing purposes. The system clock is 40MHz, so the ADC clock is 20MHz. This board has a potentiometer wired to Port E0, which I've configured as ADC1, channel5. I've tested this port assignment using the provided driver, "A2D_GetSingleCh_ADC1(ch)" and that works fine. When using the PWM-CTU-FIFO-DMA, the data values are appropriate, but their location in the array written to by DMA from the FIFO is odd. Specifically, the values that I'm seeing in FreeMaster indicate that the bit for ADC0 is indicated with a "1" and ADC1 is indicated by a "0". Also, I expect the result from ADC0 to be written first, before ADC1, since ADC0 conversion is faster, but I'm seeing the opposite. Seems like my interpretation of ADC1 and ADC0, or the documentation, is reversed.

The following screenshot from FreeMaster indicates that ADC_result[0], the first value in the result from the FIFO is ADC0? Channel 5, with a value of 0x3Fe, (I have the potentiometer maxed at 3.3V). I see alternativing ADC1, ADC0 in the results, (expected) and I can connect the pot to any port and see the appropriate value change, (if I wire the pot to port E7, then ADC_result[7] tracks ADC_result[0]. If ADC 0&1 were reversed, this is the ADC order that I would expect. So I'm just wondering why ADC0 & 1 appear reversed from what I expect?

a) ADC1 result appears first in the FIFO, insted of ADC0 which has a faster conversion time;

b) ADC1 is indicated by a zero in the ADC results (Ref Man. 25.4.3 ADC result), and ADC0 is show with a "1".

5 bits in the upper 16 bits indicate the ADC unit (1bit) and the channel number (4 bits).

ADC_result[7] 0x1A 02 00 "1" is suppose to be the ADC #, but it is ADC_0.

Here's how I configired the CTU ADC command list (triggered off PWM VAL0).

// ADC1B, ADC0A, shift ch_b left one bit
CTU_0.CLR[0].R = 0x60A4; // 5, 4 dual, first
CTU_0.CLR[1].R = 0x20C8; // 6, 8
CTU_0.CLR[2].R = 0x20E9; // 7, 9
CTU_0.CLR[3].R = 0x21EA; // F, 10
CTU_0.CLR[4].R = 0x4000; //first, stop
CTU_0.TH1.B.THRESHOLD0 = 0x7; /* one less thatn # of FIFO 0 entries.*/

//------------------------------------------ADC channel initialization.

void ADC_Init (void)
{
   ADC_0.MCR.R = 0;                  //MCR 0x8002-0000
   ADC_0.MCR.B.OWREN = 1;           //overwrite enable
   ADC_0.MCR.B.CTUEN = 1;           //CTU mode
    ADC_0.NCMR[0].R = 0x00F0; //000-0111-1110-0000 enabled conversion channels
    ADC_0.CTR[0].B.INPCMP = 2;       //1.2us at 20Mhz
    ADC_0.CTR[0].B.INPLATCH = 1;
    ADC_0.CTR[0].B.INPSAMP = 13;
    ADC_0.CTR[0].B.OFFSHIFT = 1;   //tranisition at 1/2 LSB

   ADC_1.MCR.R = 0;                  //MCR 0x8002-0000
   ADC_1.MCR.B.OWREN = 1;           //overwrite enable
   ADC_1.MCR.B.CTUEN = 1;           //CTU mode
    ADC_1.NCMR[0].R = 0x80E0; //000-0111-1110-0000 enabled conversion channels
    ADC_1.CTR[0].B.INPCMP = 0;       //3us at 20MHz
    ADC_1.CTR[0].B.INPLATCH = 1;
    ADC_1.CTR[0].B.INPSAMP = 14;
    ADC_1.CTR[0].B.OFFSHIFT = 1;   //tranisition at 1/2 LSB
}

Re: dual conversion, ADC channel order question

petervlna — Fri, 30 Dec 2016 10:26:52 GMT

Hi,

I'm quite confused of this long explanation.

But when is selected dual conversion ADC0 is converted and then ADC1. The ADC0 result is stored first in FIFO and ADC1 as second.

So If you read the FIFO you will read first ADC1 and then ADC0.

Peter

Re: dual conversion, ADC channel order question

duanemattern — Fri, 30 Dec 2016 15:38:45 GMT

Peter, sorry if it was too long.

I was trying to be complete, but I guess I didn't do a good job explaining the question.

I appreciate the help and the feedback.

Regarding a) Your comment says "ADC0 result is stored first"; "ADC1 as second"; "read first ADC1 and then ADC0".

Your response seems to imply that while the ADC0 conversion completes first, it's written to the 2nd address of the FIFO [1], and ADC1 conversion finishes second, but written to the 1st address of the FIFO [0]. { I'm not looking at the FIFO memory address, I'm looking at an array written to by the DMA transfer process, but it appears to process them in order.} The behavior seems odd, as secion 25.4.2 of the reference manual indicates that "ADC unit 0 has the priority, otherwise the first ADC that ends its conversion will write as first in the FIFO". And since ADC0 is faster than ADC1, I would have expected ADC0 to be written first (index [0] in the array). I guess it is a skewed FIFO, First In, Second Out? If that's the behavior, then okay, I just wanted to confirm it.

Regarding b) the Analog Unit Number, you didn't comment on this. I showed in the screenshot for ADC_result[0] = 0x503fe, the Analog Unit Number is reported as zero, with the channel number as five, and a value of 0x3FE: 00-05-03-fe.

I know that this is ADC1, ch5, as it is the Potentiometer on the TRK-MPC5604P board, connected to Port: PE0

So I guess in this case zero means ADC1 and one means ADC0, which seems odd, but since it isn't specified in the reference manual, I guess it is okay, but I just want to confirm it.

I just trying to confirm that the behavior is valid and that I've not configured the device improperly.

What I really want to confirm is that ADC0 is faster than ADC1 in terms of conversion, as this result does not seem to confirm that.

Thanks again for the feedback.