topic Re: DMA setup with ADC16_RA as source in Digital Signal Controllers

DMA setup with ADC16_RA as source

TurboMan — Tue, 24 Jun 2014 14:57:25 GMT

Hi,

just asking this here as I can't get this to work. I can set up a RAM to RAM DMA transfer which works ok, I can trigger this with a timer, and that works. But I want to configure a timer or trigger to set the 16bit ADC converting, then transfer the data to a buffer.

However, when I select ADC16_RA as a source, it doesn't work. It says "bus transfer terminated with an error on the read portion of the transfer". This indicates the address for ADC16_RA is wrong, but I've double checked and even put the address in had coded. The ADC result register should stay the same, the buffer address should increment, the data width is 16bits wide; All these things work ok when a RAM to RAM tansfer is set up.

Any help / information would be great, thanks.

Regards...

Re: DMA setup with ADC16_RA as source

arpitaagarwal-b — Wed, 25 Jun 2014 11:07:52 GMT

Hello,

Is your source register is getting incremented after every transfer?

if so, check DMA_DCR_SINC bit. It should be 0 to keep the source address constant after every DMA transfer.

Can you share the complete DMA initialization code.

-Arpita

Re: DMA setup with ADC16_RA as source

xiangjun_rong — Tue, 08 Jul 2014 05:50:20 GMT

I do not know whether you have solved your issue or not. I suspect you use MC56F84xxx or MC56F82xxx, which have DMA module. Regarding your problem, pls refer to section 13.3.3 Destination Address Register (DMA_DARn) in MC56F847xxRM.pdf, the DMA_DAR and DMA_SAR must have byte address rather than word address.

Pls use the following code:

#define FQSPI0_SPDTR 0xE0B3

unsigned int array[SIZE]={

0x3355,0x00FF,0x3355,0x00FF,0x3355,0x00FF,0x3355,0x00FF,0x3355,0x00FF,\

0x3355,0x00FF,0x3355,0x00FF,0x3355,0x00FF

};

/DMA do the transfer function from memory buffer to SPI transmitter reg

void DMA_init()

{

//initialize the DMA0

//DMA0, 2, SPI0_RF Reciever Full, triggering source

//DMA1, 2, SPI0_TE Transmit Empty,triggering source

DMA_REQC=0x20000; //set SPI0_TE trigger DMA

DMA_SAR1=(long)&array[0]<<1;

DMA_DAR1=(long)FQSPI0_SPDTR<<1;

DMA_DSR_BCR1=0x04;

DMA_DCR1=0x70642000;

}