basic stamp and I2c bus

rapter

HI,

I am new to the basic stamp. I am retired and have decided to build a robot. I have completed the platform and run it around using a joystick no problems ( it weighs in at 200lbs. ). In looking around for the proper brain for it I have looked at the Oopic and basic stamp. When I came across the add for the MSRS Boe-Bot I decided go that route to get my feet wet. I have run the Boe-Bot all around the house using my laptop and MSRS. Now I am ready to move on and transfer to my large robot.

My problem is I want use the CMPSO3 electronic compass and from what I understand I need to use I2C bus for the compass. I know I will have to purchase the BS2P stamp for that but I can not determine if I need to replace the board of education or not in order to use I2C bus. Any help greatly appreciated.

allanlane5

Any 24-pin BS2 'flavor' will plug in to the BOE, no problem.

It IS possible to make an I2C bus with a 'plain' BS2, but the BS2p does have special commands for it. Meaning it would take more code and work more slowly in a 'plain' BS2.

rapter

Thanks for the reply. It looks like my best bet is to buy the BS2P and use it on my BOE. I looked a little closer at the BOE doc and believe I now understand now.

Thanks ED

Larry

You won't need to upgrade to a 2p just to read the compass (though you may wish to for other reasons).
the CMPS03 also has a PWM output with pulse width proportional to heading.


a few lines of code make it easy to interface with your Stamp, and I've found the output to be just as accurate as the I2C method.
here's a code snippet provided by the manufacturer for the different available Stamps:

bearing var word

main:
  pulsin 8, 1, bearing                          ' Get reading
  bearing = (bearing-500)/50                    ' BS2(e) - Calculate Bearing in degrees
  ' bearing = (bearing-1250)/125                ' BS2sx - Calculate Bearing in degrees
  ' bearing = (bearing-1333)/133                ' BS2p - Calculate Bearing in degrees
  debug 2,1,1, "Compass Bearing ", dec3 bearing ' Display Compass Bearing
  goto main                                     ' around forever

further explanations here:

www.robot-electronics.co.uk/htm/cmps2pwm.shtml

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