AP_HAL_ChibiOS:modify hwdef for V3 of ReaperF745

[Hwurzburg]

now either rename to just ReaperF745 or split changes into a new hwdef based off the v2...I prefer the former
tested on V3 board....has the same funky 45 deg vehicle forward as the V2...

I sent Andy P a link to the build to test on his V2 to make sure it still works

[Hwurzburg]

renamed rather than create a separate V3 hwdef

[Hwurzburg]

space was down to 2K, free space by minimizing GPS and Airspeed backends

[andyp1per]

Please try 16Mhz

[Hwurzburg]

Please try 16Mhz

@andyp1per we discussed in devcall and it was felt that trying this on a single board does not prove the board layout over production is guaranteed to support it, hence the use of a more conservative clock on most boards...those boards that do use it had OEMs that verified on multiple boards....and there was the uncertainty of real benefit...

have you had a chance to test on a v2 board?

[andyp1per]

we discussed in devcall and it was felt that trying this on a single board does not prove the board layout over production is guaranteed to support it, hence the use of a more conservative clock on most boards...those boards that do use it had OEMs that verified on multiple boards....and there was the uncertainty of real benefi

The issue is that because of the clock tree the actual speed on the boards I have tested come out significantly lower that 8Mhz. Setting to 16Mhz usually ends up with a speed of about 12Mhz, which is conservative enough but much better than the 6Mhz or so that you get otherwise. This is a small board with short traces - as far as I am concerned picking 8Mhz is just as much finger in the air as anything else. However, the reduction in CPU duty cycle when you go with higher clock speeds is very significant.

I've not had a chance to try with v2 as yet.

[tridge]

However, the reduction in CPU duty cycle when you go with higher clock speeds is very significant.

there is no change in CPU load. When waiting for the SPI completion interrupt the thread is suspended, so no CPU usage. Note that if you use the disable-interrupts method to try to measure CPU then you will see higher CPU, but that is because the CPU is artificially locked to the thread.