I can’t seem to keep microstepping from jumping on (any of my) A4988 boards at any current setting. The little Nema 17 motors jumps/or loose steps about 1:8 steps, and it does fine on the others. I have a 2 amps of power supply, and 660mf of capacitance on my 12v rails, and a 10uf on the 5V coming from an arduino, and still it’s jumping, even with a heatsink affixed, or without.
I have a question: Is the ROSC pin pulled down?
It’s hard to trace, but the ROSC on the board seems to go through a via, along a trace, and it looks like it might end up where a part has been omitted.
It’s okay to make the board a little bigger. I’d rather the boards had been made with:
- 1cm clear from the main chip for easier mounting for a heatsink, perhaps mounting the other components on the bottom where there seems to be room given the header supplied. Yes, I know that you can’t put anything under the chip because its heatsunk : )
- Jumpers for microstepping, with a built-in pullup resister on MS1, if it still needs it.
- A jumper for the ROSC, and the sleep/reset combination.
- Keep the original pinouts in parallel so that people can still such things as put the chip to sleep, and do coarse stepping.
BTW, I have had good results mounting a tiny heatsink using Artic Alumina non-conductive heatsink epoxy. It’s boron nitride and aluminum oxide, and allow nice heat transfer: arcticsilver.com/arctic_alum … hesive.htm
Thank you for your feedback. The ROSC pin is pulled down. Did you see the board schematic at the bottom of the product page? We haven’t had others report problems like this, and given that you are experiencing this issue with multiple boards, I think there is likely a problem with your setup. Unless you’re keeping the current limit set below 1 A, your power supply sounds insufficient. What are you using for power? Can you post the code you’re using?
I just finished testing the setup with a 7AH VRLA battery, and it does the same thing. In 16x microstepping, after 1:8 steps, it jumps, and I can hear it jump. The 5V is coming from the arduino and I have plenty of capacitors, all around.
Looking at page 12 of the specsheet, your breakout board appear to have use a different resistor arrangement than the spec sheet has. The spec sheet has a simple resistor between ROSC and ground; your schematic appears to have a voltage divider.
The pull-up resistor (R2) on the schematic is marked as NP, which means not populated. How fast are you trying to step it? Can you look at your power voltages on an oscilloscope while you are stepping? Can you post a picture of your setup?
Just to clarify, does the skipping only occur in 16th microstep mode?
No, I’ve noticed the jumping in a few of the microstepping modes, which seem to occur at 1/2 of the micro-stepping, such as at 1/16, it seems to do it every 8 steps and so on.
Are you sure it’s skipping steps rather than just experiencing uneven step sizes? Can you provide me with more information about your stepper motor?