GP2D02 to OOPic Example

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Introduction
Circuit Schematic
Source Code

Interface setup for using a GP2D02 to a OOPic controller.

Introduction

In this example, an OOpic microcontroller uses a Sharp GP2D02 detector to measure distances to obstacles. The program clocks in bits from the GP2D02 detector and assembles them into an 8-bit distance measurement. The program turns on two LEDs when this value is within a desirable range. It turns on only one of LEDs when the distance is either too near or too far.

Contents

Circuit Schematic

The following schematic assumes the OOPic has power. When the GP2D02 is taking a measurement, it has an average current draw of 22ma so it can be powered by the OOPic's 100ma onboard regulator. The pin selections match those in the source code listed below.

This circuit uses an interface diode to prevent the HIGH logic level of the OOPic's output from exceeding the 3.3 volts allowed at the VIN input of the GP2D02 detector. This diode is included with and described in the instructions of the GP2D02 package. The VOUT output connects directly to an OOpic pin. All that remains is hooking up two LEDs.

Wiring diagram of the GP2D02 to OOPic example.

Contents

Source Code

This code uses BASIC syntax. It runs with version 3.0.1 of the OOPic compiler and version A.1.7 of the OOPic chip.

The Sharp GP2D02 has strict timing requirements for clocking out the data bits. The code uses an oOneShot object to generate short clock pulses on the VIN input line. Pulses that are too long will reset the GP2D02. The routine to read the GP2D02 has two consecutive commands to set VIN high in order to reset the sensor. Repeating the instruction twice adds enough delay to satisfy the 1.5ms time required to reset the sensor properly.

The GP2D02 is ideal for microcontrollers without analog-to-digital conversion capability. However, since the OOPic has ADC inputs, it is usually simpler to use GP2D12 sensors on an OOPic.

' filename: GP2D02-5.osc ' This program reads the distance to an obstacle from ' the Sharp GP2D02 sensor and controls two LEDs ' in the following manner: ' ' #9 #8 ' too close 1 0 ' just right 1 1 ' too far 0 1 ' ' Such a program could be the starting point for a ' simple wall-hugging robot. dim bit1 As New oDio1 dim bit2 As New oDio1 dim bX as new oByte sub main() bit1.Ioline = 9 bit1.Direction = cvOutput bit2.Ioline = 8 bit2.Direction = cvOutput call setup02 do call read02 if bX.value<100 then bit1.value=0 else bit1.value=1 end if if bX.value>120 then bit2.value=0 else bit2.value=1 end if loop end sub '----------------------------------------------------------- dim bitVIN as new oDio1 ' VIN green dim bitVOUT as new oDio1 ' VOUT yellow dim ii as new oByte ' counts bits dim qq as new oBit ' input to one-shot dim bitCLK as new oOneShot ' sends short clock pulses to GP2D02 sub setup02() bitVIN.Ioline = 12 bitVIN.Direction = cvOutput bitVOUT.Ioline = 13 bitVOUT.Direction = cvInput bitCLK.Input.Link(qq.value) bitCLK.Output.Link(bitVIN) bitCLK.Operate=cvTrue end sub sub read02() bitVIN.value=1 ' VIN high for 1.5ms bitVIN.value=1 bitVIN.value=0 while bitVOUT.value=0 ' wait for measurement to finish wend bX.value=0 for ii.value=1 to 8 bX.LShift qq.set ' trigger one-shot to clock the GP2D02 qq.clear bX.value=bX.value or bitVOUT.value next ii.value end sub

Revision History:

2000-07-11: Example Created.
2000-08-14: Added version info for OOPic compiler and OOPic chip used in this example.