What do folk think of the xsrf4po?

[Andy7]

There's a handful of things that I want to upgrade on my quad:

- Move up from my (VERY TRUSTY, and I love it still) Naze32 F1 FC
- Add some OSD (especially things like vbat)
- Upgrade my radio.. and so need a new RX
- Use the LED strip that my Naze currently won't support due to UART clash

The new(ish) xsrf4po  from FrSky seems to do all but be a new radio(!) in one painless hit. Doesn't matter that it's a little longer than the usual square form as I've got bags of space in my frame.

Anyone have any strong opinions on this FC? Looks like I can get it for £50 which I could probably even get past MY missus!! 

[Tryingto]

Before taking the plunge, seriously pro is having a clear out sale - http://shop.seriouslypro.com/flight-controllers

You can get a decent official fc for £15 (was £47.50), leaves another £15 for an rx and your in at £30. Definitely get that past the wife

[Andy7]

Nice... but looks like they're out of the OSD+VTX boards.  ... (but that doesn't really matter)

[Cheredanine]

Not overly impressed with Frsky flight controllers, but not particularly worse than others.

[Andy7]

lol - level mode engaged for on-the-fence balancing :)

Was there anything in particular that you weren't so sure about ont he FrSky FCs?
I kind of like the nice and neat solution that this one seems to give - plus, I can hand down my old electronics to Josh so he can have a crack at building a quad.

[Cheredanine]

Early Frsky were based on the sprf3, which isn’t the best fc, specifically at the time it was still running I2c to the gyro years after everyone had moved to spi

[Andy7]

Oh, that's not so bad then. i2c is pretty fast, but I guess on a small board like that, the SPI bus will be able to run right up to the sampling limits of the sensors then.

[Cheredanine]

I2c will allow up to 4khz max.
Gyro sample rate gets big benefits from being fast, nyquist limit means you can only accurately read up to half the sampling rate, so with I2c in the best possible situation you can only ready up to 2khz

Whilst this means you can easily cope with stuff like prop fundamental freq (around 200hz) noise above the nyquist limit will create aliasing.

I have run at least 8khz for a couple of years now and have many quads running up to 32khz, I don’t subscribe to ultra high pid/motor loops but two things I do run as fast as I can that make a difference to quad feel are gyro sampling and motor pwm rate from the esc (blheli32 at 48khz is very smooth).i would not intentionally use an fc with I2c to the gyro.

Now the board you reference probably doesn’t, but Frskys first fc had I2c to an mpu9250. 2 years after we moved away from I2c and invosense had public stated that gyro was nit appropriate for quads, just symptomatic of bad design decisions.

Maybe that board is fine, but I haven’t bothered looking because there are plenty of boards our there that don’t make that kind of dumb design decisions

[Andy7]

Thanks for that, all makes sense. Looks like it DOES have an SPI bus, which I can see is a MASSIVE speedup on I2C given that it's more of a direct Master to slave bus rather than the more 'polite' I2C with all it's bus negotiatios and things slowing stuff down.
Sensor is an MPU6000.

[Cheredanine]

Yeah the issues I listed were from the first fc they released, which was f3, but the issues were broadly well known two years before they released the board. Not saying that f4 will have them, saying they make glaring obvious errors of design in general, maybe they have learned from them, but there are plenty of fc manufacturers that don’t make that kind of dumb mistake.
MPU6000 is the best of the old generation, most modern fc are running imu605XX nowerdays.

To be clear, I don’t have any issues with that fc it may well be fine, I haven’t looked at it, my issues are with the pedigree of the company making it in this field, there are no shortage of options.

[Andy7]

Sure, that's fine - but great to get some good IN DEPTH advice there down to the chip-level.
I'll do a bit of hunting to see what issues folk have in practice but unless it's a disaster it's going to be a good step up from my Naze32.r5 and I can ratchet up my flying skill and tuning a bit with the extra sensor data.
I kind of get the feeling that I'm outgrowing the Naze now.