DRV2624EVM-CT: External Trigger Pin J17

Hey Zach,

Thank you for reaching out.

Can you tell me if the other modes of trigger work as in pulse and software trigger?

Also what is the VDD level you are using with the device?

Best,

Carson Allen

LPAA Team

Hi, Thank you for the response. All the other modes of trigger work within the software. I'm powering the unit using USB.

Hey Zach,

Is it possible for you to provide the Vdd of the board to the input of J17 to test if that works as an enable?

I am worried you might not be providing enough voltage but having the input = Vdd should definitely work

Please try that and get back to me.

Best,

Carson

So, I did this. I anticipated a ground reference issue and tried to manually jumper VDD to J17 Trigger and it killed the board. After discussing with an EE colleague, they seemed to think that the 430 pin needs to be tri-stated. Also, that the board encountered issues because of jumpering from an 5V supply to a 3.3V system.

I'll monitor the voltage while doing this. Where would you suggest I put the ground ref? My new board just arrived today. VDD to trigger pin did actually toast the board. I got the smell and it would no longer enter GUI mode. 

I monitored the voltage on the trigger with reference to the board's ground ring. It's only seeing about .1 V despite setting the function generator to 2V amplitude 1Hz pulse of DC. My function generator is limited to 2V max on DC/Square. Do you see any other way to external trigger without adding another piece of equipment?

I was able to get the desired pulse using the waveform sequencer, but I'd like for overdrive and braking to be disabled. Is this possible in waveform sequencer?

Hey Zach,

When you say you got the desired pulse, do you mean were able to correctly pulse the trigger?

Yes you would need to run the device in open-loop mode and make sure auto-braking in open-loop is disabled. These are controlled by bits 6 & 4 in register 0x08.

Best,

Carson Allen

Hi Carson,

I was not able to correctly pulse the trigger, but I was able to generate an on demand pulse with the sequencer. I'm looking to trigger short pulses of pure sine waves. Generally, I would base this on the desired number of cycles, but I can still do it by calculating the time. This is actually more desirable because it removes one instance of triggering in the sequence. So, to confirm, I was able to trigger from the Ext pin using a higher voltage. That issue is resolved.

On another note, I can't seem to figure out quite how the Vrms and ODVoltage work. For instance, If I have Vrms set to 0.9 and ODV set to 1.25, I end up with a 0.9 amplitude sine wave rather than a 0.9 Vrms sine wave.

Hey Zach,

If you run in open-loop the Vrms set by the RATED_VOLTAGE parameter is ignored and the amplitude of the waveform is based on the data you programmed into the RAM memory, ODV will still clamp the voltage at 1.25 V.

Best,

Carson

I'm running in closed loop though.

Hi Carson,

Thanks a bunch for all your help. I finally think I have this thing figured out. I'm pretty much now getting what I would like from the device. Seeing the equations just made everything clear.