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Re: [Paparazzi-devel] BMP085 sensor temperature wiht large error

From: Martin Mueller
Subject: Re: [Paparazzi-devel] BMP085 sensor temperature wiht large error
Date: Fri, 05 Aug 2011 19:39:38 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20110617 Lightning/1.0b2 Thunderbird/3.1.11

Hi Mr. Warmers,

can you be a little more specific? In the master branch I only see the EstimatorSetAlt() getting called in the baro_ets (and the outdated MS5534 driver). In case of the baro_ets it does not get set then by gps in estimtor.c:216. The BMP085 or SCP1000 driver currently do not feed the Kalman altitude filter.


On 05.08.2011 18:16, Prof. Dr.-Ing. Heinrich Warmers wrote:
Sehr geehrter Herr Müller,

vielen Dank für die schnelle Korrektur.
Können Sie sich auch mal den Aufruf des Höhenfilters ansehen?
Bei mir war es so, dass sowohl im Treiber als auch in estimator.c ein
Aufruf erfolgte.
Mit freundlichen Grüßen

Heinrich Warmers

Martin Mueller schrieb:

Hi Helge,

the extra noise is from reading the lower three bits of the pressure
result wrongly. They are in the higher bits of the XLSB, not the
lower, fixed in master:

@@ -130,7 +130,7 @@ void baro_bmp_event( void ) {
/* get uncompensated pressure, oss=3 */
bmp_up = (bmp_trans.buf[0] << 11) |
(bmp_trans.buf[1] << 3) |
- bmp_trans.buf[2];
+ (bmp_trans.buf[2] >> 5);
/* start temp measurement */
bmp_trans.buf[0] = BMP085_CTRL_REG;
bmp_trans.buf[1] = BMP085_START_TEMP;

Thanks for looking into that.

As the max conversion time is 25.5ms it could be run at 30Hz without
changes, maybe having the temp reading only once per second as
suggested in the spec. Some averaging could be done depending on the
frequency you need.


On 04.08.2011 11:36, Helge Walle wrote:

To make sure that the sample rate is not set so high that it interferes
with the conversion time of the BMP sensor, I would need to check the
data flow with my logic analyzer.
I did not do that yesterday evening. However, Increasing freq from "8"
to "20" in .../paparazzi/conf/modules/baro_bmp.xml increased the data
flow and did not create any problems.
The code I used with my Arduino board that made better results was from
Sparkfun. I am quite determined to work through the code since I feel
sure that this is the right way to go.


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