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DAC80508EVM: Data converters forum

Part Number: DAC80508EVM
Other Parts Discussed in Thread: DAC80508

Hi Everyone,

Trying to get some form of comms to this DAC (DAC80508M)

The following is my SPI setup:

The MCU is an stm32f7.

The clock polarity is low and the clock phase is set to 2nd edge.

I have tried a range of clock speeds, but it's currently set to 3.375MBit/s.

The MSB is sent first.

According to the standalone operation section from the datasheet this configuration seems correct?

The DAC:

The internal reference is used and the SDO/ALRM pin has a 10k pullup on it.

The code:

I think my issue would relate to the order that I'm updating or accessing the DAC registers.

Here's the steps I follow:

I setup my first payload as the following:

1) I initially update the config register

Read/write = 0x0

Address = 0x3

Data = 0x3200

uint32_t payload = (0x0 << 20) | (0x3<< 16) | 0x3200;

Therefore, all the dacs and reference is powered up. The pin is set as an alam pin.

2)Then I update the Gain register

According to this the gain setting needs to be set to x2 and div setting needs to be set to /2 to get 0V to VREF operation.

Read/write = 0x0

Address = 0x4

Data = 0x01FF

uint32_t payload = (0x0 << 20) | (0x4 << 16) | 0x01FF;

Finally I write to the sync register to ensure that the data register it updated immediately after a write to the dac data register.

Read/write = 0x0

Address = 0x2

Data = 0x0000

uint32_t payload = (0x0 << 20) | (0x2 << 16) | 0x0000;

After this in my opinion a write to a dac data register should show a change in the output voltage. Yet the voltage remains at the midscale voltage.

For instance the following should update dac channel 0 to a voltage value of 0V

Read/write = 0x0

Address = 0x8

Data = 0x0000

uint32_t payload = (0x0 << 20) | (0x8 << 16) | 0x0000;

Any chance anyone knows what I'm doing incorrectly? 

Thanks in advance for any help! 

  • Hi Randy,

    Akhilesh will be able to help you tonight.  Thanks!

  • Hi Randy,

    Your configuration seems fine to me. Can you post scope shots of your SPI frame? Are you able to read the default registers?

    Also a rough sketch of how you hooked up EVM to STM32 controller will b helpful here.

    By default internal reference is powered up, Can you try to disable the same by writing into OCNFIG register to verify that the SPI packets received by device correctly?

    I am assuming you are working with SPI mode 1 as per the post, that's fine for DAC80508.  Also you can leave the SYNC register contents as is 0xFF00, no need to write into these unless you want LDAC trigger.