DAC8760 interface with MSP430

Hello Mitesh,

Do you know what class of HART device you are looking to develop (2-wire, 3-wire, 4-wire)? 

The DAC8760 is not a low-power current DAC, and is specified for 3-wire or 4-wire designs. If you are looking to design a loop-powered transmitter, you may want to consider the DAC161S997 with an external BJT.

As far as finding information useful to you, you may want to reach out to the HART Communication Foundation, and they will be quite helpful in assisting you in getting information.

Also, although we do not currently have any evaluation kits for HART, be on the lookout for a few TI Designs which are currently in the works. One TI Design will show an MSP430 operating as a HART Modem, while the other will be a full sensor transmitter design which interfaces with the DAC161S997 and an ADS1220 for measuring an RTD.

Let me know if you have any other questions on this.

Hello Tyler,

As I told I am very new to this technology, it would be helpful if you can tell me which would be the easies method to start with. 

I have got DAC8760 IC with package of TSSOP-24.

I have aalso gone through the following link.

http://www.ti.com/lit/an/slaa572/slaa572.pdf

But I am still bit confused how to start with? So if you can just get me the initial step to start with this, I can carry ahead and can reply back on this as well as other posts for reference.

Regards,

Mitesh

Mitesh,

I'm not entirely sure what you need help with. Interfacing with the DAC8760? Choosing the correct MSP430 for a HART application? Creating the SW stack for the HART protocol?

A HART field transmitter has four basic sections to it: a sensor interface, the analog current loop, the digital FSK transmission, and the SW stack for the HART protocol.

• If you are planning on using a 16-bit DAC, you probably want to use a 16-bit+ ADC (external AFE). Documentation on those AFEs (ADS1220, etc.) will help with the sensor interface portion.
  • Another option for the front end would be to utilize the MSP430i2041 and the SD24 module for the sensing portion of your application.
• The document you cited (as well as the datasheet for the DAC8760) will help you with controlling the current loop, as well as how to couple in the FSK to the loop current.
• For creation of the digital FSK modulation, you can use a standalone HART module, or you can emulate the FSK yourself by modulating those frequencies using a Timer/PWM.
• The SW stack for HART is available online for free for some platforms, but would need a bit of modification to work on the MSP430.

As I stated in my previous post, we are working on two TI Designs (one of which should be published by the end of the year) which will exponentially help customers develop with HART. My advice would be to utilize these solutions when they become available.

Until then, you can draw from the TI Designs TIDA-00095 and TIDA-00165 to put together a full current loop solution, on top of which you can add the HART FSK abilities.

Hello Tyler,

Sorry was stuck up with some high priority projects under me and would like to come back on this again.

I already have a product where I have interfaced DAC8760 to get current output. Now I would like to carry ahead with the same project so that the project should be HART Enabled. 

I have to use ISET-R pin / HART IN pin from DAC8760 IC as in present product we are not using QFN package.

I have also read that we have to give HART Input and get current output, but exactly I have not understood by the statement. Do I need external communicator? I am also little confused of what exactly HART Enabled device means? Do we need a Software for PC? What about HART protocol Stack?

I would be pleased if you can clear above querries to proceed ahead.

Regards,

Mitesh 

Mitesh,

For questions specifically about the operation of the DAC8760, I would suggest you post these questions to the Precision Data Converters Forum.

For your other questions:

• What is a HART enabled device? -- A HART enabled device is a device which can send/receive digital commands and data via the HART protocol over a current loop (4-20mA) system.
• Do we need a Software for PC? -- Many HART tools will have an interface to the PC, but it is not a requirement.
• What about HART protocol stack? -- There are some HART protocol stacks available for both master and slave devices for free on the web. Chances are the porting and amount of work needed on your side will not make that a worthy venture. As I alluded to earlier, we are working on a TI Design which will incorporate a full HART stack which will be available for licensing through a third party as well.

Again, please consult the DAC experts for assistance with their specific parts. If you have any MSP430-related questions, please feel free to continue this thread here.