using cogs for S2

jphill

I'm learning to program the S2 and have run into a problem when I attempt to use multiple cogs. It will seem to execute the program correctly for a short time (maybe a few seconds maybe a fraction of a second). Then it will go crazy. Random wheel movements, random lights, the Parallax Serial Tool shows random digits.

I tried to follow the steps in this tutorial, but I think it is less useful because it is not written for the scribbler.

http://gadgetgangster.com/tutorials/326

Does anyone have code they've written for the Scribbler that uses multiple cogs. I'd like to try to see if it is something wrong with my machine.

Mike Green

It's not an issue of using cogs with the Scribbler 2, it's an issue of how you're using them. The symptoms you're describing sound like a stack overflow or one cog's code accessing an array out of bounds so it's writing over data or code elsewhere in memory, not a hardware problem. Post your code as an attachment to a reply.

jphill

Thank you for writing back. I increased the stack space to 50 longs and the problem went away. I did wonder where that stack space comes from. Is there an easy way to guess how much I will need for a given piece of code? How much can I distribute to different cogs before I run out of memory?