Altitude hold problem

[ashta]

In my Quad when i use
dev20110725, version, the altitude hold is working reasonably.
while when i use Multiwii 1.8 patch2, or Multiwii 1.9, it works but jumps up and down.
Attached pl find the screen shot of Mutiwi configurator with
1. dev20110725
2. Multiwii ver 1.8 patch2

pl note that with dev20110725 the ALT value displayed is 207.88
while with Multiwii ver 1.8 patch2/ 1.9 it is 864.20

My "debug 2" is always zero.

is this normal? or is this the reason why it is not working.

Also, i had to comment the line" Trusdted accelerometer" for the stable mode to work?

For altitude hold, does the " Trusted accelerometer" have to work? i do not think so since with dev20110725 it was reasonably working.

or with Multiwii 1.9, is there a systematic PID tuning required. Can some body give me a pointer for this.?


your kind help appreciated.

[ashta]

hello friends,
pl kindly reply to this problem of mine.
thanking you

[kalle123]

What sensors are you using ???

Tell a little about your hardware.

BR - KH

[ashta]

hello Kalle123,
I have made my own board. Attched pl find the Picture.
I use
ITG3200
BMA180
BMP085
HMC5883
1.5 K pull up for the I2C lines.
Level convereter
On board 5V and 3.3V regulator

No errors in Debug2 window with 1.9 SW

thanks a lot

ashta

What sensors are you using ???

Tell a little about your hardware.

BR - KH

[timecop]

You shouldnt need untrusted acc (i.e TRUSTED_ACCZ commented OUT) on properly made hardware.
its only needed for failcases of people ghettoing up a bunch of crap breakout boards.
it should really be renamed to
#define MY_HARDWARE_IS_BROKEN

[ashta]

but if i do not comment it, it is not stable when accelerometer is enabled.

[timecop]

So your accZ decreases when you run motors and throttle up? (The only case for needing trusted accz).

[ashta]

yes. but pl give me some tips to make it work!
it was kind of working with the dev version dev20110725
and why is
" with dev20110725 the ALT value displayed is 207.88
while with Multiwii ver 1.8 patch2/ 1.9 it is 864.20"

[Alexinparis]

yes. but pl give me some tips to make it work!
it was kind of working with the dev version dev20110725
and why is
" with dev20110725 the ALT value displayed is 207.88
while with Multiwii ver 1.8 patch2/ 1.9 it is 864.20"

Hi,
I remember I did some float to integer simplifications about alt calculation,
but the values are correct on my side.
There is probably something wrong somewhere...

However, the important thing is the accuracy of altitude variation, not the absolute value.

[ashta]

thanks Allex. i will try some PID tuning and will report

[timecop]

I noticed there was another change in bmp085 pressure calculation,

> b7 = ((uint32_t) (bmp085_ctx.up >> (8 - OSS)) - b3) * (50000 >> OSS);
in multiwii now

> b7 = ((uint32_t) bmp085_ctx.up - b3) * (50000 >> OSS);
in reference code from sparkfun or so

with the line1, i was getting 200k pascals as output of pressure_calculate (wrong)
with line2, i was correctly getting ~100k (I live at sea level).
I knew this because my hardware can just set a breakpoint inside bmp085_calculate and I knew the returned value. no idea how you can confirm the calculation on your board.

[ziss_dm]

Hi,

This is probably because you did shift here:

Code: Select all

bmp085_ctx.up = ((((uint32_t)raw[0] << 16) | ((uint32_t)raw[1] << 8) | ((uint32_t)raw[2])) >> (8 - OSS));

regards,
ziss_dm

[timecop]

Oh, haha, good catch. So disregard that, I suck.