Intel Edison generic calculator shield photo journal

[Paul Dale]

(04-02-2015 04:43 AM)MarkHaysHarris777 Wrote:  I hope you're right; your sentiments are at least encouraging.

I think you'll be surprised what is possible. As an example, at a previous job, we managed real time decode and playback of two MP3 streams under Linux on a 90MHz ColdFire processor. It consumed about 70% of the CPU but it worked and the audio didn't stutter or glitch. It was a lot of work and there were plenty of rather difficult to track bugs but it was possible. Moreover, the unit had a front panel with menu and was capable of downloading more music over the Internet -- again without glitching the music playback.

Quote:...I want the MCU to refresh the display, as well scan the keyboard. I have already tested this in the Edison and in the Raspberry; and what happens is that as the kernel adjusts the time slices for the various running processes the display refresh 'sketch' process does not get an even-consistent running time---which causes the display to have a 'strobing' or 'throbbing' maybe even 'flickering' effect at times (which is very annoying) especially if the kernel (or other processes) gets very busy.

Two thoughts here:

1. You could run the display refresh process at one of the high batch/real time priorities. These have the nice feature that they completely preempt any lower priority process and their timing is usually pretty good. The down side is if one of these locks up, there is nothing you can do.
2. Why are you using multiple processes in the first place Unix/Linux has good support for event driven programming and a single thread/process is usually better than lots of threads -- not when you want to exploit the parallelism but most of the rest of the time.
   

Quote:The second activity that requires *very* precise timing is using the 'calculator' (even the generic calculator shield) as a scientific data gathering station....

This is very different. This is hard real time. I somewhat suspected you were planning something like this when I responded before


- Pauli