DAC7562 12bit SPI DAC programming problems.

[Rob_975]

Hi there.

I'm having hard times to menage the DAC7562 DAC via SPI.
I use a PIC18F67K22@48MHz and the SPI bus is working (oscilloscope tested).
I use the SPI PIC hardware pins: 34=clk, 35=data in, 36=data out.

first, the SPI configuration.

[Ttelmah]

Several things....

spi_write, sends just 8bits. Look at the manual...

Get rid of the setup_spi. #use spi, and setup_spi, are _alternatives_ and should not be used together.

With #use SPI, you use spi_xfer to send data.
This can be set to send longer word lengths, in the #use spi.
Data is clocked on the falling edge, so 'mode 1'

So, syntax is:

[RF_Developer]

You must also initialise the DAC by setting the gains and enabling the reference, etc. before it'll generate any voltages.

[Ttelmah]

Hurrah, somebody who looked further into the data sheet than me.

Best Wishes

[Rob_975]

Perfect, it works.
Just a little more thing.
For me the easiest way to write the 24bit word is in binary (because with the registers table I can easily set the proper bit):

[temtronic]

comment: as to the error , you can't have spaces in the 0bxxxx format.

'space' is NOT a valid binary character, only '0' and '1' are

same holds true for any 'format',

0x1234 is good; 0x12 3 4 is bad.

hth
jay

[Ttelmah]

As a comment, 'better way', I'd say was not to use values in the command at all.
#DEFINE them.

Think for a moment about things like #use SPI. You don't set them up with commands like:
#use spi(something=0b110010000)

instead the compiler authors have defined for you, nice constants that as their 'name', also give a hint to what is being done. So:

#define SETA_722volts 0x00C000

Then really, you should try to get used to reading hex. It is far easier to 'not' make a mistake about positioning, since effectively the hex value is just 4bit groups of binary digits, so:

0x00C000 = 0000 0000 1100 0000 0000 0000

which is effectively what you are trying to do.

Then the other thing is to combine values together (as you see in several of the CCS constants, with |).

#define SETA_volts 0x000000
#define SETB_volts 0x010000
#define V752 (0b110000000000<<4)

Then you can set the value with:

dac=spi_xfer(id,SETA_volts|V752 ,24); //set out_A=7.522V

Now the V752, is defined as the 12bit value 'placed' where it needs to be (four bits left).
Key here is that things like this are solved at _compile_ time, not in the chip itself.

Generally putting long numbers for things like register patterns directly 'in' the code, is a fairly 'sure' sign of relatively inexperienced programming.

Best Wishes