DRV8824 /25 decay control?


For my project, I need to be able to control decay mode (mixed/slow/fast). That’s leg #19 of the 8824/25 IC. On Pololu boards, this leg is left disconnected (or at least it looks that way), so the IC, according to PDF manual, always operates in mixed decay mode. In order to get access to IC’s decay control interface, I had to solder a very tiny wire directly to leg #19. I wished there was an easier way to access it, but the driver documentation didn’t provide any clues.

Am I missing something? It’s hard to beleive there’s no way to access such an important feature of the IC without doing a very difficult modification I mentioned.

Gene Fedorov

Hi, Gene

No, you are not missing anything; on the current board we do not have a way to access that feature. These boards were designed to be compatible with our older A4988 modules, so we had to make some choices about which pins we could bring out.

We have not heard this request before, and we would be interested in hearing form others who want such a feature. We are planning a carrier board with a different form factor that will bring out that pin, but it will probably be at least a few months before that is available.



Thank you for your answer. I hope very much that there will be a version of the board (md20c or md20d perhaps) which has a pin connected to leg #19. Personally, I’d gladly sacrifice EN, secondary GND, FLT, RST, SLP, or any combination of them, for that purpose. With certain combination of voltages, step settings and running speeds the default (mixed) mode causes steps to be skipped; this behavior makes the driver useless for high-precision applications (such as camera control) unless decay mode interface can be accessed somehow.