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m3pi
The m3pi robot consists of an mbed connected to the Pololu 3pi robot
The 3pi contains a low level MCU that takes care of motor control, optical sensors and other hardware oriented functions. When the 3pi is programmed with the stock "slave" firmware, will make this functionality available through an API over a serial port.
The m3pi consists of an mbed Microcontroller running the high level functions and control algorithms, implemented by API calls to 3pi hardware. The mbed Microcontroller is then free run protocol stacks and communications interfaces (bluetooth, Zigbee, Wifi and so on) as well as control algorithms, mass storage for preprogrammed routines and so on.
Hello World!¶
This simple program will drive the m3pi forward, spin it left, reverse it and spin it right.
Import program
00001 #include "mbed.h" 00002 #include "m3pi.h" 00003 00004 m3pi m3pi; 00005 00006 int main() { 00007 00008 m3pi.locate(0,1); 00009 m3pi.printf("LO World"); 00010 00011 wait (2.0); 00012 00013 m3pi.forward(0.5); // Forward half speed 00014 wait (0.5); // wait half a second 00015 m3pi.left(0.5); // Turn left at half speed 00016 wait (0.5); // wait half a second 00017 m3pi.backward(0.5);// Backward at half speed 00018 wait (0.5); // wait half a second 00019 m3pi.right(0.5); // Turn right at half speed 00020 wait (0.5); // wait half a second 00021 00022 m3pi.stop(); 00023 }
| You Tube Clip |
Hardware¶
There is very little connectivity required between the mbed 3pi work
| mbed | 3pi |
|---|---|
| Ground | Ground |
| Vin | Vcc |
| p8 | nRST to the 3pi |
| p9 (from mbed) | RXD (to the 3pi) |
| p10 (to the 3pi) | TXD (from the 3pi) |
Library and API¶
Import library
Public Member Functions |
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| m3pi () | |
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Create the
m3pi
object connected to the default pins.
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| m3pi (PinName nrst, PinName tx, PinName rx) | |
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Create the
m3pi
object connected to specific pins.
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| void | reset (void) |
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Force a hardware reset of the 3pi.
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| void | left_motor (float speed) |
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Directly control the speed and direction of the left motor.
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| void | right_motor (float speed) |
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Directly control the speed and direction of the right motor.
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| void | forward (float speed) |
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Drive both motors forward as the same speed.
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| void | backward (float speed) |
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Drive both motors backward as the same speed.
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| void | left (float speed) |
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Drive left motor backwards and right motor forwards at the same speed to turn on the spot.
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| void | right (float speed) |
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Drive left motor forward and right motor backwards at the same speed to turn on the spot.
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| void | stop (void) |
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Stop both motors.
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| float | pot_voltage (void) |
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Read the voltage of the potentiometer on the 3pi.
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| float | battery (void) |
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Read the battery voltage on the 3pi.
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| float | line_position (void) |
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Read the position of the detected line.
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| char | sensor_auto_calibrate (void) |
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Calibrate the sensors.
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| void | calibrate (void) |
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Set calibration manually to the current settings.
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| void | reset_calibration (void) |
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Clear the current calibration settings.
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| void | leds (int val) |
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Write to the 8 LEDs.
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| void | locate (int x, int y) |
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Locate the cursor on the 8x2 LCD.
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| void | cls (void) |
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Clear the LCD.
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| int | putc (int c) |
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Send a character directly to the 3pi serial interface.
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| int | getc () |
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Receive a character directly to the 3pi serial interface.
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| int | print (char *text, int length) |
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Send a string buffer to the 3pi serial interface.
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Resources¶
Useful numbers¶
- Speed of rotation: 720 degrees per second at half speed
- Forward/Backward: 470mm per second at half speed