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Adafruit DRV2605L Haptic Motor Controller Sampling Rate
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Adafruit DRV2605L Haptic Motor Controller Sampling Rate

by GeneralSpud on Tue Jul 21, 2020 3:47 am

Hello,

I am looking into using a DRV2605L motor controller for a project requiring haptic feedback, but within the documentation I cannot find any mention of a sampling rate for the controller. Does it vary between using ERM and LRA motors or is it consistent between the two?

Many thanks

GeneralSpud
 
Posts: 3
Joined: Tue Jul 21, 2020 3:40 am

Re: Adafruit DRV2605L Haptic Motor Controller Sampling Rate

by oesterle on Tue Jul 21, 2020 6:51 pm

Hi, GeneralSpud!

Welcome to the Forums!

If you're asking about the sampling rate for the audio-to-vibe mode, there are details in section 7.6.11 of the DRV2605 datasheet, which is linked in the CircuitPython and Arduino sections of the primary guide.

In closed-loop modes, the driver can also sample the back-EMF coming from a motor, enabling optimizing the haptics to a particular motor.

I mostly use the other, simpler modes, driving a vibe motor with the library of 100+ haptic patterns built in to the DRV2605.

What are you making?

Cheers,

Eric

oesterle
 
Posts: 763
Joined: Tue Sep 17, 2013 11:32 pm

Re: Adafruit DRV2605L Haptic Motor Controller Sampling Rate

by GeneralSpud on Tue Jul 21, 2020 6:56 pm

Hello,

Thanks for getting back! I'm making a prototype for haptic feedback for a myoelectric prosthetic.

I'm not the one making the prosthetic, so whatever I make needs to be easily portable.
The person making the prosthetic had questions about the hardware I was using, including the DRV2605L, so I'm doing some research on its specifications.

With regards to sampling rate, I am not very familiar with it as a concept, nor what it might imply. For instance, I see in the documentation that there is a range of values between 100-200 Hz. Does this mean that the sampling rate can vary between 100 and 200 samples per second? Additionally, I also don't have a good gauge of if this is a good enough sampling rate for this project. What would be considered a 'high' sampling rate versus a 'low' sampling rate?

Many thanks,

GeneralSpud

GeneralSpud
 
Posts: 3
Joined: Tue Jul 21, 2020 3:40 am

Re: Adafruit DRV2605L Haptic Motor Controller Sampling Rate

by oesterle on Tue Jul 21, 2020 7:28 pm

Cool! Looking forward to hearing about your progress.

In my experience, triggering a short haptic click from the DRV2605L library is pretty fast, so I'd suggest starting with those. The inexpensive Adafruit Vibrating Mini Motor Disc works well. That's an ERM motor; LRA motors also work well for me, and can do more nuanced patterns with faster transients.

For LRA motors, in Arduino I modify the example code to call drv.useLRA() and drv.selectLibrary(6), like this:

Code: Select all | TOGGLE FULL SIZE
void setup() {
  Serial.begin(9600);
  Serial.println("DRV test");
  drv.begin();
 
  drv.useLRA();
  drv.selectLibrary(6);
 
  // I2C trigger by sending 'go' command
  // default, internal trigger when sending GO command
  drv.setMode(DRV2605_MODE_INTTRIG);
}

If you'd like to share a photo or sketch of your project, that will help. What microcontroller and myoelectric sensors are you using?

You can upload images here, using the File Upload section below your reply. Images around 800x600 work best here.

Cheers,

Eric

oesterle
 
Posts: 763
Joined: Tue Sep 17, 2013 11:32 pm

Re: Adafruit DRV2605L Haptic Motor Controller Sampling Rate

by GeneralSpud on Wed Jul 22, 2020 6:18 pm

Hi Eric,

I don't have a set plan for my design yet. Right now I am trying to figure out what parts to order.

I am planning to base an initial design for a single finger on this project:
https://www.instructables.com/id/Moonwa ... rosthetic/

It's meant for diabetics but I feel it can be adapted for a hand prosthetic.

Instead of the coin vibrator used in the project, I am planning to use this one from solar robotics:
https://solarbotics.com/product/vpm2/

As its frequency range is between 150-250 Hz which from what I've read is generally used for skin haptic feedback.

Eventually, I will want to move on to including all five fingers. One concern I have with the DRV2605L is if it can handle more than 1 vibrating disk motor, or will each motor need to have a designated controller?

Many thanks,

GeneralSpud

GeneralSpud
 
Posts: 3
Joined: Tue Jul 21, 2020 3:40 am

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