Re: SRF04.c - wrong range for filter (line 145)

[Jonathan Cameron <jic23@jic23.retrosnub.co.uk>]

+CC Andreas.

On Mon, 17 Jun 2019 21:21:37 +0200
Zbyněk Kocur <zbynek.kocur@fel.cvut.cz> wrote:

> Hello,
> 
> I try to use linux kernel module for proximity sensor SRF04 and i was not able to measure distance longer than 1.5 m. The problem is on implementation maximum range filter in function srf04_read, line 145. The reasoning assumes that the distance to 3 meters is limited, but the direction back and forth is neglected. Therefore, the resulting limit is a maximum of 1.5 meres and not a required 3 meters. The solution is to come out of the formula:
> 
>                  *         distance       2 * 3 m
>                  * time = ---------- = --------- = 18808777 ns
>                  *          speed       319 m/s
>                  *
> 
> 
> Best Regards,
> Zbyněk Kocur
> ---
> email: zbynek.kocur@fel.cvut.cz
> phone: +420 224 354 054
> web: http://www.fel.cvut.cz
> Department of Telecommunications Engineering
> Faculty of Electrical Engineering
>