I am building ultrasonic system that needs to generate three different signals for three transducers at the same time.The system is controlled via DSP. Currently I have a DAC with 4 outputs, but as I understood it can only update either one output at a time with different value or all of them but with the same value. My new idea is to use three DACs, but I am trying to figure out how to simultaneously update different values to them. I could use different McBsp and SPI ports of DSP eval board that are clocked, but how to make the execution of transmission parallel? Any ideas?



  • \$\begingroup\$ If each transmitter is only going to correspond to a single receiver then I do not see why you need to synchronize all three transmitters. \$\endgroup\$ – DKNguyen Apr 13 '20 at 16:04
  • \$\begingroup\$ I would like to implement a CDMA channel access method, where I send three different signals, receive them with one transducer and then compute three times matched filtering in order to see what are the distances between the transmitting transducers and a receiving one. \$\endgroup\$ – Deanna77 Apr 13 '20 at 16:10
  • \$\begingroup\$ Ah, I see...... \$\endgroup\$ – DKNguyen Apr 13 '20 at 16:19

I am trying to figure out how to simultaneously update different values to them.

LDAC appears to be the pin that simultaneously loads all DACs: -

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You just need to ensure that the channels you want to be synchronous are configured to be synchronous: -

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  • \$\begingroup\$ Yes, but the value to be sent to all of them is the same value. And I would need three different values. \$\endgroup\$ – Deanna77 Apr 13 '20 at 16:11
  • \$\begingroup\$ No it isn't. You can load separate values to each DAC register then activate all DACs together. I'll edit my answer to show where you are confused. \$\endgroup\$ – Andy aka Apr 13 '20 at 16:14
  • \$\begingroup\$ But then I would have three SPI transmissions for loading and on the fourth one I would have the conversion? I also have an ADC connected to the same SPI, with the same clock, and should have synchronized transmission and reception. Then I should use a different slower clock for ADC? \$\endgroup\$ – Deanna77 Apr 13 '20 at 16:21
  • \$\begingroup\$ Correct and, if that doesn't give you the throughput speed then you have to find a way of increasing it (possibly by parallel operations with different SPI bus interfaces to physically different DACs). I can't answer about the ADC. My answer is confirmation that you can activate three DACs simultaneously inside the DAC80504 with different values (contrary to your initial understanding as stated in your question). \$\endgroup\$ – Andy aka Apr 13 '20 at 16:25
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    \$\begingroup\$ @Deanna77 If this does not answer your question and meet your needs then you definitely need to update your question. To me, this sounds like exactly what you need. What does "use three DACs in parallel" mean then? \$\endgroup\$ – Elliot Alderson Apr 13 '20 at 17:52

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