Timing Query!

[Mike]

Hi,

I’m generating my own ‘PWM signal’ on the crumble to control the position of an SG90 servo motor.

I can get 8 positions on the servo using ‘no op’ codes to cause a sub-millisecond delay loop.

However, when I disconnect the USB and run the crumble and servo off a 5v battery, the timings change! In fact I seem to get *more* positions (11), suggesting that the crumble processor is running *faster* when NOT connected to the USB.

1) Does this make sense to you?

2) What is going on?

3) How can I fix it so that when I program the crumble via USB it will give the same ‘PWM signal’ as when I disconnect it?

Many thanks!

[Joseph]

Hi Mike,

Yes, that does make sense. The Crumble maintains the USB connection while connected to the PC. I.e. it doesn’t use a boot loader. It has a little virtual machine that runs your program, the VM and USB routines are polled in turn, so if the USB connection is not present that function will return quicker.

Not sure if you can fix it at the moment. I am working on a new version of the VM which will hopefully include servo outputs though.

Thanks,

Joseph

[Mike]

Ah! Okey dokey. I will muddle through for now 🙂

Servo output for the motor pads would be AMAZING!

[Joseph]

Hopefully it’ll be on the ABC and D pads 🙂

Joseph

[Mike]

ABCD would be brilliant – I’m getting to grips with servos and they are AWESOME!

I don’t suppose you have any kind of timescale on this? 🙂

[Joseph]

Erm… < 1/0 days 😉

[Mike]

Hi Joseph,

Did you get anywhere with servo output? Would be great to have!

🙂

[Simon]

If you can’t wait for native support – 4Tronix have produced a Servo Crumb
http://4tronix.co.uk/store/index.php?rt=product/product&path=82_84&product_id=503

Simon

[Mike]

Hi Simon, I was really just wondering how long it might take to see this feature? This thread goes back 4 months… :/

The 4Tronix crumb would be great, but it is twice the price of a servo on it’s own, and the crumb itself is so large it makes it impossible to use it the way I want to. 🙁

Do you know how long it might be before this feature is implemented? Some kind of ETA would allow me to plan.

Many thanks! 🙂

Mike

[Author]

Posts