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DAC8560EVM on MMB0 w/DXP

Lou DiCerbo
Prodigy 50 points
Other Parts Discussed in Thread: DAC8560EVM, DAC8560, DXP

I finally got my DAC8560EVM board working on a MMB0 motherboard using the DXP program. Everything seems to be working OK but I cannot figure out how to disable the internal voltage reference so that I can apply an external reference. I try to send the x480401 command but only 24 clock pulses are generated before the /FSX line goes high. The DAC8560 requires at least 26 clock pulses with /FSX held low in order to execute the command. I tried sending x4804010 but only 24 pulses are sent. I even tried to change the W6 jumper on the DAC8560EVM board to pins 1-2 to hold the /CS line low while sending 2 frames (x480401 and x000000) and this did not work. I do not know what else to try.

  • 0
    TI__Expert 5815 points

    Hello Lou,

    Both 4 V and 5 V reference sources can be selected via W8 and W4 jumper configurations as mentioned on page 9 of the user's guide.    Have you populated both jumpers as referenced below?   

    Regards,

    Sem Amesawu

  • 0
    TI__Genius 10615 points

    Hello Lou,

     

    The original code did not allow for the 2 extra CLK cycles required by the reference enable/disable sequence. I attached a new file that will allow you to control the device as well as to input the manual codes to enable.disable the reference.

    7840.DAC8560REF.xml 
    <?xml version="1.0"?>
<device>
  <name>DAC8560REF</name>
  <revision>1.0.0</revision>
  <date>03Sep2014</date>
  <devicesettings>
    <instructionwidth>32</instructionwidth>
    <channels>1</channels>
    <format>sbinary</format>
    <dataword>XXXXXXCCDDDDDDDDDDDDDDDDXXXXXXXX</dataword>
    <commanddefault>0</commanddefault>
    <commandlatch>0</commandlatch>
    <maxupdaterate>1000000</maxupdaterate>
    <interface>
      <type>spi</type>
      <polarity>1</polarity>
      <phase>0</phase>
      <maxsclk>30000000</maxsclk>
      <framebits>32</framebits>
    </interface>
    <latchpin>
      <feature>0</feature>
      <pulsepol>0</pulsepol>
    </latchpin>
    <FSplus>2.5</FSplus>
    <FSminus>0</FSminus>
  </devicesettings>
</device>

    • Copy this file into the DXP Devices directory. (Typically C:\Users\Public\Documents\DXP\Devices)
    • Launch DXP and it should automatically detect the new file.
    • Search for the new DAC selection. The name should be DAC8560REF.

    The new code uses 32 CLK cycles, this means that you need to pad the Manual Command Write with two zeroes on the right. The rest of the software behaves the same as the original.

     

    Reference disable:

    0x48040100

     

    Reference enable:

    • Power cycle the device, OR
    • Send the following two sequences:
      1. 0x4C040000
      2. 0x49040100

    If you have any issues, please let me know.

  • 0 in reply to iConduct
    Prodigy 50 points

    I apologize if I did not clearly describe the problem that I am having. The problem is not with using an external reference for the DAC8560EVM. The problem is that I cannot disable the internal referenve according the write sequence specified on page 19 of the DAC8560 datasheet (see attached). It is clearly specified that both the internal and external references cannot be used simultaneously so I need to disable the internal reference. My external reference will be supplied from TP1 of the DAC8560EVM and will vary from 100mV to Vdd.

    dac8560 Internal Vref.pdf
  • 0 in reply to Lou DiCerbo
    TI__Genius 10615 points

    I understand the issue. I apologize for not being very clear in my explanation above.

    The DAC8560 SPI interface uses 24 CLK cycles during normal communication.

    In order to disable the internal reference sending the code 0x480401 is necessary, plus 2 extra CLK cycles. A total of 26 CLK cycles.

    The device file that the software was using did not allow for the extra CLK cycles. I modified the device file to accommodate for these 2 extra CLK cycles. Due to limitations in the software I can not make it 26 CLK cycles, but 32 CLK cycles. This is why the codes that I provided, end with 0x00.

    Lou DiCerbo said:
    It is clearly specified that both the internal and external references cannot be used simultaneously so I need to disable the internal reference.

    Using the new file (DAC8560REF.xml) will allow you to power down the internal reference using the manual command code 0x48040100, before using the external reference.

    Should you need to disconnect the external reference and power on the internal reference, you can power cycle the device or use the codes I provided below.

     

    New device file solution:

    7651.DAC8560REF.xml 
    <?xml version="1.0"?>
<device>
  <name>DAC8560REF</name>
  <revision>1.0.0</revision>
  <date>03Sep2014</date>
  <devicesettings>
    <instructionwidth>32</instructionwidth>
    <channels>1</channels>
    <format>sbinary</format>
    <dataword>XXXXXXCCDDDDDDDDDDDDDDDDXXXXXXXX</dataword>
    <commanddefault>0</commanddefault>
    <commandlatch>0</commandlatch>
    <maxupdaterate>1000000</maxupdaterate>
    <interface>
      <type>spi</type>
      <polarity>1</polarity>
      <phase>0</phase>
      <maxsclk>30000000</maxsclk>
      <framebits>32</framebits>
    </interface>
    <latchpin>
      <feature>0</feature>
      <pulsepol>0</pulsepol>
    </latchpin>
    <FSplus>2.5</FSplus>
    <FSminus>0</FSminus>
  </devicesettings>
</device>

    • Copy this file into the DXP Devices directory. (Typically C:\Users\Public\Documents\DXP\Devices)
    • Launch DXP and it should automatically detect the new file.
    • Search for the new DAC selection. The name should be DAC8560REF.

     

    Internal reference disable:

    • 0x48040100

     

    Internal reference enable:

    Power cycle the device, OR send the following two sequences:

    1. 0x4C040000
    2. 0x49040100

     

     Hopefully this is a little clearer.

  • 0 in reply to Eugenio Mejia
    Prodigy 50 points

    Eugenio,

    Your response was quite clear the first time. The new code works fine. I just haven't had the chance to respond right away. Unfortunately, the .xml files are not readily available on the TI website. The download utility in DXP does not connect properly and I had to go through the forums to find out how the do it manually.

    Thank You for your help.