AVR Freaks

The DAC uses the Start Conversion event to load data from DATABUF into DATA and start a new conversion. In the SAM D21 case, dac_async_write will write data to the DATABUF register, so the Start Conversion event should be configured properly to use this asynchronous driver.

Looks like the D51 async driver also depends on event control for the DAC. You have configured event input for start conversion but there is no event. If you want to try this without event control then change here

void _dac_async_write_data(struct _dac_async_device *const device, const uint16_t data, const uint8_t ch)
{
    hri_dac_write_DATA_reg(device->hw, ch, data);
}

i.e., this function normally writes to DATABUF, by writing to DATA it can work without input event.
Note to change also the START config, i.e., make sure the DAC "Start Conversion Event Input DAC 0" is not selected.

Also move  the 

dac_async_write(&DAC_0, 0, example_DAC_0, 10);

out of the while loop in main (i.e., do it once, it's done from the callback after that).

BTW, when I try this (Samd51j18a_firmware_Example_DA.zip  modified as mentioned) there is also something not optimal with (maybe) the clock setup, it takes 2 - 15 seconds from reset until there is a signal on VOUT0.
/Lars

Hi Karthika,

i have some similar problem getting the DAC on the SAMD51 working.

I have the decreasing and increasing, too.

If i am in debugging mode on an breakpoint, both channels working correct.

If i let the code run, both channels output voltages increase or decrease.

I read every datasheet page three times and absolutely dont know whats going on.

Did that mean that you only use one DAC channel or both at the same time on the same value ?

Thats some point i never try. I will try that tomorrow.

OK that sounds interesting.

I am able to generate two different values with restriction. Maybe the Code helps you?

But i see you use the c++ style programming?

My restriction is that its not possible to do something other as write values into a loop in the data Register to hold the Output voltages.

Although the REFRESH period is set! If i do something other, the output values increase or decrease to VDD and GND.

The same happenes, and thats very interesting if i set the Current Control to 1MSPS. Although my GCLK_DAC is 8 MHz the whole

thing is now set to <= 1,2 MHz (100kSPS) to get the DAC working.

Could it be that the DAC isnt able to generate autonom infinity conversions?

void DAC_Init()

{

REG_MCLK_APBDMASK |= 0x00000200;                   //DAC Bus clock enable

REG_GCLK_PCHCTRL42 = 0x0000044;                    //Quelle: 8 MHz GCLK4

REG_DAC_DACCTRL0 |= 0x0002;                        //DAC0 Enable

REG_DAC_DACCTRL1 |= 0x0002;                        //DAC1 Enable

REG_DAC_DACCTRL0 |= 0x0200;                        //DAC0 Konfig (REFRESH = 0x2 ;current control = 0 (100 kSPS))

REG_DAC_DACCTRL1 |= 0x0200;                        //DAC1 Konfig (REFRESH = 0x2 ;current control = 0 (100 kSPS))

REG_DAC_CTRLB = 0x06;                              //Vref = internal bandgap reference 2,5 V

REG_DAC_DBGCTRL = 0x01;                            //Debug Control (DAC continous normal operation)

REG_DAC_CTRLA |= 0x02;                             //DAC Enable

while( (REG_DAC_STATUS & 0x1) == 0 );              //Wait until DAC0 Ready

while( ((REG_DAC_STATUS & 0x2)>>1) == 0 );         //Wait until DAC1 Ready

REG_DAC_DATA0 = 0x0CCD;                            //2 V = 3277 = 0xCCD

REG_DAC_DATA1 = 0x0666;                            //1 V = 1638 = 0x666

while(1)

{

while( (REG_DAC_STATUS & 0x4) != 0x4 );

REG_DAC_DATA0 = 0x0CCD; //2 V = 3277 = 0xCCD

while( (REG_DAC_STATUS & 0x8) != 0x8 );

REG_DAC_DATA1 = 0x0666; //1 V = 1638 = 0x666

}

}

@ jcandle

Did that mean that you tested out the internal bandgap reference too and it doenst work ?

For me it would be interesting because my problem is that the automatic refresh doenst work.

I cant testing out the external reference because the pin is not free.

A friend of me contacts Microchip during his work. As answear they send him a code-snipped with

VDDANA as DAC reference. Thats so stupid ^^.