PM Standard - HW Watchdog issue...

Author	Message
Grogster Admin Group Joined: 31/12/2012 Location: New Zealand Posts: 9956	Posted: 08:59pm 08 Oct 2025         Volhout said   Grogster, You are designing a MM2 in WS-Zero footprint to have a drop in replacement for the WS-Zero in your application ? Just for the watchdog issue ? Or also because of the lower power supply current of the MM2 ? For a couple of reasons, actually. I only ever started using the PM, as I kinda HAD to. During COVID, chip shortages were a big issue, and I simply could not buy the 170 MM2 chips from Microchip Direct - they were all out of stock, with lead times of up to a year, and even THAT wasn't guaranteed. So, looking around I found the PM that Peter had recently ported MMBASIC to, so I started using them, as they were cheap and readily available, unlike the Microchip chips. But I decided to just go forward with the PM - why bother to re-invent the wheel, right? But I always preferred the MM2 chip. Now I have quite a few boards out there designed for the WS-Zero module, so in order to avoid having to replace them all(or to hack them to fit an external WD circuit), I came up with the idea of the WS-Zero footprint compatible MM2 module idea.   The thing that decided it for me, was discovering no "RUN"/reset pin on the WS-Zero module, so interfacing an external WD circuit requires at least some kind of hack, with a wire to the RESET tact switch.  That complicates things, so I though I had enough reason to design a replacement module, which will get me back onto the preferred MM2 chips now I can get them again from Microchip without issue. This also means I don't have to worry about WS stopping production of the Zero module moving forward, which they could do at any time - now I can produce a MM2 module in WS-Zero footprint, that I know I can always build when needed. It seems very likely I will have to visit each of those units to update the software to get around this issue, so if I have to do that anyway, why not just swap the module out for a MM2-based replacement at the same time. That's kinda where my thinking is at this point, anyway. I particularly like your discrete WD timer circuit using just a couple of MOSFETS. I'm tempted to see if I could squeeze that into the WS-Zero footprint module I am working on, but it would be a tight squeeze!