Sensors/AMSYS

2015-06-30T15:18:35Z

Niko: The links to the user guide were changed to the manufacturer's website, so that the most recent version of the datasheet and the user guide can be obtained. Amsys is a distributor of AMS 5812.

<categorytree style="float:right; clear:right; margin-left:1ex; border: 1px solid gray; padding: 0.7ex;" mode=pages>Sensors</categorytree>

This site will explain a way, how to use a Analog Microelectronics pressure sensor - AMS 5812 Series, distributed by Amsys.

==Addressing==
At first you have to be sure, you've programmed the right I2C address on the sensor chip. 
To do this, you can use a programmer device named “AMS 5812 starter kit“ which comes with all the software you need.
http://www.analogmicro.de/_pages/sens/ams5812/ams5812_usersguide_starterkit.pdf

===Paparazzi addresses===
I2C Addresses:
The default address of every AMS chip is F0 and it is always reachable, even if you've programmed a other one.

The default addresses defined in the paparazzi driver are:
*Baro: 0xE4
*Airspeed: 0xE8

You can change them and many othe sensor specific data in the files:
*/sw/airborne/modules/sensors/baro_amsys.c
*sw/airborne/modules/sensors/airspeed_amsys.c

===AMSYS addresses===
The „AMS 5812 starter kit“ software does not use the first bit of the address. 
If you want to know more see: 
http://www.analogmicro.de/_pages/sens/ams5812/ams5812_data_sheet.pdf 
Because of this you have to program the sensor chips with this addresses:
*Baro: 0x72
*Airspeed: 0x74

==Airframe==
This is an expample to define the module in the airframe.

<source lang="xml">
<firmware name="fixedwing">
...
<define name="USE_I2C0"/>
<define name="USE_AIRSPEED"/>
...
</firmware>

<modules>
<load name="airspeed_amsys.xml">
<define name="AIRSPEED_SCALE" value="1."/>
<define name="AIRSPEED_FILTER" value="0.902000010014"/>
</load>
<load name="baro_amsys.xml">
<define name="BARO_FILTER" value="0."/>
</load>
</modules>
</source>

USE_AIRSPEED is only needed if you want to control your plane's speed by true airspeed.

This is the calculation which should explain the usage of AIRSPEED_SCALE 
sqrtf(2*(pressure_amsys)*airspeed_scale/1.2041);

1.2041 is the value of the air density.

AIRSPEED_FILTER and BARO_FILTER are values of an TP1 filter:
<source lang="c">
airspeed_amsys = airspeed_filter * airspeed_old + (1 - airspeed_filter) * airspeed_tmp;
airspeed_old = airspeed_amsys;
</source>

The AMSYS Baro driver is only written to measure the height not to use it as an flight variable.

[[Category:Sensors]] [[Category:Modules]]

PaparazziUAV - User contributions [en]

Sensors/AMSYS