ADC12130: configuring the ADC 12138

Hi Rohan,

Can you share your schematic and timing diagrams showing the commands you are sending to the ADC12138?

Hello Tom ,

Please see below wiring diagram . 

Pins CONV, PD, AGND, DGND VREF+/- ,COM connected to Ground.

SCLK = 100Khz , CCLK = 5Mhz

not using EOC signal .

following commands are being sent 

0x0A : Power up

0x08: Autocal command

wait for 1 secod for EOC

0x09:Autozero command

wait for 1 secod for EOC

0x8D: Sign bit command

wait for 1 secod for EOC

0x0C: Read status

0x0C: Read status

wait for 1 secod for EOC

0x90: Select channel 2 , single ended.

Protocol.SPI.ReadWrite(8,[2])  ...reading two bytes of 8 bits data.

is data on MISO line not sampling correctly ?

any instruction is missing in the code ?

SCLK and CCLK shoudl be shorted or have same frequency ?

Please check and provide suggestions.

Thanks

Hi Rohan,

First - Vref+ needs to be something other than ground, usually it is going to be 4.096V as shown in Figure 63.  The conversion process uses the (stable, clean) reference voltage to compare against the voltage captured on the ADC input.  If the reference is 0V, the conversion results will always be 0.  I'll assume you have the ground pins of the Digilent tied to the same ground as your circuit.  SPI mode 0 is correct, so what do you see on the output after writing the Read Status command?

@Tom Hendrick , Vref+ is connected  to the +5V supply. grounds are tied to digilents ground .As datasheet says ,  Auto cal  command and then two Read status commands , you should see the status register data on MISO line. In the below image ,  the data  on MISO line is 00H for the same. 

Hi Rohan,

Can you follow the sequence of Figure 62?  Send 12 to 16 clocks with the Read_Status and then see what get from the DO pin?

Hello Tom ,

so all the configuration commands like Autocal, read status should be  sent with 16 clocks ? and the output data (12 bit , no sign)  to be sampled with 12 clocks ? 

in datasheet , if the CS pin  is continously low then  it says to send 13 SCLK pulse ? 

in figure 62 , 12 clock pulses are sent .

In Figure 62, the /CS is being strobed, the first sequence above (your red circle) is the command and the second frame (8 SCLKS) has the STATUS data.  Both frames can be 12 clocks wide for ease of use with your controller.

Hello Tom ,

 Autocal command ( once )  -> Read status command  (twice) -> channel selection command  (once) , and then  i should see the actual data on DO Pin . is that correct ?

Yes, I believe so.

And the output data to be sampled should be with 12 clock cycles i.e 12 bits of 1 word  ? with MSB bit first out ? 

var c=Protocol.SPI.ReadWrite(12,[1])

is it necessary to send the channel selection command twice ? becuse i see 12bit +sign written twice ?

Correct - MSB can be first or last though

The second channel selection is for another channel, or another conversion on the same channel.

is it possible to get a sample code of initialization just to get kick started in this ?

Hi Rohan,

Unfortunately we do not have any sample code to share with you.  I've ordered some sample units for myself and will try to get some detail for you.  It will take a few days though...

Looking forward to hear from you once you get the IC's . 

I tried and  succeeded till getting status register values correct but the conversion data observed on DO pin was not correct and kept changing .