bcm2835_peri_write

[Wolfram Köhn]

I use bcm2835_gpio_write to generate Pulses for a stepper motor. This function calls  bcm2835_peri_write containing two __sync_synchronize() calls.

This works fine for most of the time but sometimes a pulse is missing. To eliminate this I had to remove the two  __sync_synchronize() calls. It is still working fine just without drops.

Can this be a solution for others who have the same problem ?

Cheers Wolfram

[Mike McCauley]

Hello,

The informationwe have is that the __sync_synchronize() are important for
ensuring that the peripheral memory transfers happen correctly. I suspect what
you are seeing is interaction between the __sync_synchronize and the linux
scheduler.

I think its fair to say that it is risky to try to do real-time control like
steppers with non-real-time linux. Have you taken steps to lock the process to
prevent scheduling/swapping?

Cheers.

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Mike McCauley VK4AMM mi...@airspayce.com
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