Re: [Paparazzi-devel] I2C Questions

[Martin Mueller]

Hello Kurtis,

> Each of these sensors uses I2C, but I am uncertain whether or not I can
> use all of these sensors simultaneously through the single I2C bus on
> the Tiny/TWOG.

Yes, that is possible. I2C is a true "bus" with the ability to run 
several slaves (e.g. sensors) with one master (e.g. Tiny/TWOG). There is 
a limit on the bandwidth that you will not reach with two devices and 
all devices do need to have different adresses.

>  From what I can tell from the
> wiki 
> (http://paparazzi.enac.fr/wiki/Airspeed_sensor#Making_hardware_known_to_the_Autopilot),
> I can set a particular I2C address for each module:
> <param name="AIRSPEED_ETS_I2C_DEV" value="i2c1"/>
> However, is there a limit to how many can be used? i.e. "i2c0", "i2c1",
> "i2c2", etc.

The "i2c1" is the number of the bus, not the address of the device. 
Usually you would leave it to i2c0 for the Tiny/TWOG and connect your 
device to I2C/J6. The new Lisa boards do have multiple I2C 
buses/interfaces and you have to choose the one you connect to.

> Also, what is the parameter name for setting the ArduIMU address?

The address is defined in the device and in the driver software. For 
ArduIMU it is 0x22 and defined in the Arduino code flashed to it. The 
ETS is hardwired to 0xEA. As they are not equal there is no need to 
change them.

> Is there anything else that I need to change to get them to work together?
> As for wiring, do I just connect the SDA and SCL of each sensor in
> parallel with each other, or in series?

Connect all SDAs and all SCLs respectively.

http://en.wikipedia.org/wiki/I%C2%B2C#Design

Martin