DAC81404EVM: Cannot Set DAC Output Registers

Hi Faith,

The DACPWDWN register (0x09) uses the last 4 bits to power up the channels. 0xFFF0 means that all channels have been powered up (the last 4 bits are all zero). The DACRANGE and DACn-DATA registers are write only meaning you can't read them back. You may have written to them successfully. 

What are the jumper settings on the EVM?

Is the CLRZ (J3) jumper open or closed? 

If the internal reference is powered down, how are you supplying the external reference?

Best,

Katlynne Jones

Hello Katlynne;

Here is the picture of my board : 

You can see the jumpers (It must be its default positions). J3 is in open position.

The connector below is J17. I connected its 1st pin to 5V. 2nd and 3rd pin to GND. 4th pin to AVDD which is 12 Volt at the moment. and 5th pin to GND.

When i checked the test pins TP1, TP2 or TP3 i could not see the voltage (0 Volt). I am writing different values to DAC output registers (0x10, 0x11, 0x12, 0x13). 

Hi Faith,

It looks like you have CLR and RST connected to the controller you are using. What is the voltage level of these signals? They should be high or the DAC outputs may be being cleared or a device reset is being triggered.

Best,

Katlynne Jones

Hello Katlynne;

CLR and LDAC cables are not connected to my controller. I could connect and change their levels if you want.

We are using RST at the initial phase of  the code.

 pinMode(_rst_pin, OUTPUT);
 digitalWrite(_rst_pin, LOW);
 delay(1); 
 digitalWrite(_rst_pin, HIGH); 
 delay(1);

Its latest pin level is HIGH.

Hi Faith, 

If you don't have the CLR and LDAC signals connected then they are pulled up to DAC_IOVDD on the EVM which is fine. You can verify that these signals are high with a meter just to be sure. 

If the internal reference is powered down, how are you supplying the external reference? It looks like you have J16 open which means the onboard 2.5V reference is not connected to VREF.

Best,

Katlynne Jones

Hello Katlynne,

I checked the CLR and LDAC pins. CLR pin is high but LDAC is low which is okay as far as i know according to default Jumper settings. 

I dont really understand the reference voltage issue could you clearify little bit what should i do ?

What i have done is that i powered the board through J17 as i mentioned above. I tested the voltage with/without J16 short circuited and with/without internal reference activated via register 0x04. But i could not get any DAC out voltage.

Best Regards

Fatih

Hello Faith,

I think you are using own controller for SPI communication. could you please share programming code and  snap of your SPI signals. I want to look sequence.

Can you able to read and write register correctly ?

Hello Anbu,

Yes i could read and write SPI registers correctly as far as i understand. As i mentioned above, i could read device ID and other registers. More, i could read GENCONFIG (0x04) as 0x4000. When i changed (0x04) and write 0x0000, i could read the register as 0x0000 and when i checked the TP11, i could see 2.5 V which was 0 Volt before changing the register. So, i could change the register 0x04 and i change the voltage reference from external to internal. Furthermore, register DACPWDWN (0x09) is starting as 0xFFFF and i could change it to 0xFFF0 by enabling channels. What it means i write and read to the registers.

As a programming code, i utilizes ParswaNath's library https://github.com/sphCow/DAC81404_lib/blob/main/main.cpp . Only difference is that i changed SPI mode from SPIMODE0 to SPIMODE2. I could snap SPI related parts for sure.

#define DAC_CS 5
#define DAC_RST 22
#define DAC_LDAC 12
#define DAC_CLR 14

DAC81404 dac(DAC_CS, DAC_RST, DAC_LDAC, &SPI, 30000000);

int res = dac.init();
dac.set_int_reference(false);

 dac.set_ch_enabled(0, true);
  dac.set_ch_enabled(1, true);
  dac.set_ch_enabled(2, true);
  dac.set_ch_enabled(3, true);

dac.set_range(0, DAC81404::U_10); //   0 -> +10V
  dac.set_range(1, DAC81404::U_10);  //  -5 -> +5V
  dac.set_range(2, DAC81404::U_10);  //   0 -> +6V
  dac.set_range(3, DAC81404::U_10); // -10 -> +10V

dac.set_out(0, (i)%65535 );
  delayMicroseconds(5);
  dac.set_out(1, (2*i)%65535 );
  delayMicroseconds(5);
  dac.set_out(2, (3*i)%65535 );
  delayMicroseconds(5);
  dac.set_out(3, (4*i)%65535);

Sorry for the code snaps. I could not copy and paste whole code into one code snap. I always get the error : 

Access Denied
You don't have permission to access "">e2e.ti.com/.../configure on this server.
Reference #18.82a0de52.1634014275.28ee01c2

For SPI or dac init parts, you can check the Parswa's library. I try to copy and paste here but it look very bad due to error above. I only changed the SPI mode from Parswa's library.

By the way, we could not get the DAC output when we use launchpad as well. I could get the same readings from SPI. Is there a hardware related problem on our board ? How could we check it ?

Best Regards

Fatih

Hi Faith,

It looks like the original library has the DAC data registers being written to in a loop:

uint16_t i = 0;
bool done = true;

void loop() {
  dac.set_out(0, (i)%65535 );
  dac.set_out(1, (2*i)%65535 );
  dac.set_out(2, (3*i)%65535 );
  dac.set_out(3, (4*i)%65535);

  i = (i+64)%65535;  
  delayMicroseconds(1);

  
  /*
  if(millis()>10000 && done) {
    dac.set_ch_enabled(2, false);
    Serial.println("ch 2 shutdown");
    for(int i=0; i<4; i++) Serial.printf("ch %d power -> %d\n", i, dac.get_ch_enabled(i));
    Serial.println();
    done = false;
  } */

}

What is your value for i in the code snippet you shared? 

Thank you,

Katlynne Jones

Hello Katlynne,

Yes it is the same code you shared which is in the library, My code is also running in the loop. I could not share the code like you did because of the error Access Denied.

Best Regards

Fatih

Hi Faith, 

Can we simplify the code to just set one DAC output to full scale (0xFFFF) instead of writing in the loop. Make sure the internal reference is enabled via register 0x04 and jumper J16 is open to disconnect the external reference. Set the SPICONFIG register (0x03) to 0, and disable the read functions in the code. Set the DACPWDWN register (0x09) to 0xFFF0. 

It will also be helpful if you can send an oscilloscope shot of the SPI frame. I believe SPIMODE 2 is correct, but I recently ran into an issue where someone had the device in the wrong mode and was still able to set the internal reference on and off, but was not able to update the DAC outputs. It will be helpful to verify that the SPI is working correctly.

Can you also try removing J2 to pull the LDAC pin high? 

Are you applying an external IOVDD external to J20? What is the position of jumper J19? 

Thank you,

Katlynne Jones 

Hello Katlynne,

I simplified the coed with : 

  dac.write_reg(0x03, 0x0000);
  dac.write_reg(0x04, 0x0000);
  dac.write_reg(0x09, 0xFFF0);
  dac.write_reg(0x0A, 0x1111);

  dac.write_reg(0x10, 0xFFFF);
  dac.write_reg(0x11, 0xFFFF);
  dac.write_reg(0x12, 0xFFFF);
  dac.write_reg(0x13, 0xFFFF);

When i do that i could get 3.8 V on DAC output. And if i do code below in loop : 

  dac.write_reg(0x10, 0xFFFF);
  dac.write_reg(0x11, 0xFFFF);
  dac.write_reg(0x12, 0xFFFF);
  dac.write_reg(0x13, 0xFFFF);

  delay(1000);

  dac.write_reg(0x10, 0x0);
  dac.write_reg(0x11, 0x0);
  dac.write_reg(0x12, 0x0);
  dac.write_reg(0x13, 0x0);

  delay(1000);

I could see that voltage output change between 3.8 V and 0 Volt constantly.

If i change the internal reference to external reference by writing 0x4000 to 0x04 register and plug the Jumper to J16 i could get the same result constantly changing from 3.8 Volt to 0 Volt (i am providing 12 V to 4th pin of J17 (AVDD)). 

However if i try to write the DAC output value (0x10,0x11,0x12,0x13) other than 0xFFFF and 0x0000 i could not get any voltage output from DAC output. At startup i change the DAC output value to 0xFFFF and i could get 3.8 V output. Then i change register value to 0x1000, then DAC output value goes to 0 V.  After that i try to change it to 0xFFFF again but i could not get any voltage output anymore 0 V.

I dont provide external IOVDD through J20, jumper position of J19 is default (2-3). You can check the jumper status from picture above.

Plugging or removing J2 jumper does not change the situtation.

I try to get the oscilloscope shot of the SPI frame but before that i want to tell the latest situation so you may get some clues from these results.

Best Regards

Fatih

Hello again Katlynne,

I added the SPI frames as i said above comment.

The code i used is : 

dac.write_reg(0x03, 0x0000);
  dac.write_reg(0x04, 0x0000);
  dac.write_reg(0x09, 0xFFF0);
  dac.write_reg(0x0A, 0x1111);

  dac.write_reg(0x10, 0xFFFF);
  dac.write_reg(0x11, 0xFFFF);
  dac.write_reg(0x12, 0xFFFF);
  dac.write_reg(0x13, 0xFFFF);

I got the SPI frame of writing DAC output registers (0x10, 0x11, 0x12, 0x13) value 0xFFFF 

Channel 1 : CS

Channel 2 : SDO

Channel 3 : SDIN

Channel 4 : CLK

First picture is frame of writing 4 dac output registers. (0x10, 0x11, 0x12, 0x13)

Second picture is frame of writing 2 dac output registers (0x10, 0x11)

Third picture is frame of writing single DAC output (0x10)

I hope it helps.

Best Regards

Fatih

Hi Faith,

It doesn't look like the complete SPI frame has been captured. I don't see the full 24bit clock on channel 4.

It seems like you might not be meeting the SPI timing requirements. The data in line stays high when you write 0xFFFF, so if you aren't meeting the timing requirements some of the '1' bits might be getting captured and some might be getting skipped and that is why you are seeing 3.8V. Can you try slowing down the clock speed to see if that helps? 

If you have an oscilloscope that can capture the entire SPI clock and a time scale so we can verify the timings then that will be helpful. If you do, Try capturing a write of 0xFFFF and 0xAAAA. 0xAAAA will let us see the data in line toggling bits.

Thank you,

Katlynne Jones

Hello Katlynne,

I checked the SPI clock frequency and saw that there is one 0 more (I set 30 Mhz instead of 3 Mhz). Sorry for silly mistake :(  When i decrease it i could see the 24 bit clock.

I have one more issue about DAC output range. After i set voltage ref to external (writing 0x4000 to 0x04), when i set dac output voltage to 0x0000 i could get 0 V, 0x1111 i could get 0.66 V and 0x5555 i could get 3.33 V. But when i set 0xAAAA or 0xFFFF i get 3.93 V. After setting hex 0xA6FE (decimal 42750) i always get the same result. I could not get more than 3.93 Volt. I set the DAC range to 0-10 V (writing 0x1111 to 0x0A) and shortcircuited J16. I supply 12 V to AVDD (J17 pin 4) and GND for pin 5.

When i change the voltage reference to internal (writing 0x0000 to 0x04) result is the same. When i change the J11 position from 2-3 to 1-2 i could get 6.53 V for 0xAAAA and 0xFFFF.  After setting hex 0xA6FE (decimal 42750) i always get the same result. I could not get more than 6.53 Volt. 

Here is the SPI frame for 0xAAAA to 0x10 : 

I think there is a misconfiguration about registers or jumpers but i am not sure.

Best Regards

Fatih

Hi Faith,

Great to hear! Please let me know if you run into any more trouble. 

Best,

Katlynne Jones