Hi Team,
We have received this inquiry from our customer,
I have a question about the DAC8742HEVM. I'm not getting a modulator output in Hart mode.
I'm testing the transmit in Hart mode and I'm not seeing an output. I checked the voltages and clocks but no MOD_OUT signal.
Regards,
Danilo
Danilo,
I've recently tested this EVM, and I tied the HART output to the HART input to check functionality. This way, I can send the HART signal and read it back with the GUI.
After starting the GUI, I first toggle the reset. Then I enable the precision reference and turn on the internal bandpass filter. I set the device to full duplex and then enter in several values in to the write column. Here, I enter in 0x11, 0x22, 0x33, 0x44, and 0x55. Then I generate the write of the HART communications.
After that I can generate the read and I get back 0x5011, 0x4022, 0x3033, 0x2044, 0x1055.
This is what the GUI looks like:
Can you check to see that there is some voltage on IOVDD? There is a test point TP2 at the top of the board for that node. The EVM should be powered by the USB2ANY and I wanted to make sure that there was power coming to the board.
Joseph Wu
Danilo,
I think that the problem is that there's a jumper in JP3 that I think should be disconnected, but I'm not sure. To check, let's set the jumpers to default settings. Here's a diagram of the board with the default jumper settings:
Blue boxes are the original jumper settings. The red boxes are extra jumpers. They're on the board, but not doing anything. At the very right there's a MOD-OUT and MOD-IN terminal that I've connected together.
Then I set up the DAC8742HEVM GUI as before an populate some values into the HART write. Note the Full Duplex and Precision Reference are on:
I then generate the write and I check my oscilloscope which is connected to the MOD-OUT and MOD-IN connection. This is what I see:
Again, I think the problem is the connection made to the JP3. Regardless, just follow my diagram to test it.
Joseph Wu
