This is the Revision A version of the Light4 RoboBrick. The status of this project is that it has been replaced by the revison B version.

Light4 Robobrick (Revision A)

Table of Contents

This document is also available in PDF format.

1. Introduction

The Light4 RoboBrick can connect to up to 4 Photo Sensors (combined light emitter with photodetector.) The inputs are done using analog to digital converters rather than just binary inputs. There are 4 potentiometers to control the current throught the light emitters and 4 pententionmeters to control the gain of the returned signal.

Picture of Light4-A RoboBrick

2. Programming

The Light4 RoboBrick is continuously reading the analog inputs from its four A/D pins. The controlling program can just read the results of the digital conversion, or it can have the result down converted into a single binary bit. Each pin has has a threshold high and threshold low register that is used for the down conversion. Whenever the digital conversion exceeds the high threshold register, the down coversion results in a 1. Whenever the digital conversion is lower than the low threshold register, the down conversion results in a 0. A hysterisis effect can be introduced by having some spread between the high and low threshold values.

After the down coversions to binary bits, the result is 4-bits of binary data. A complement mask can be used to selectively invert individual bits in the 4-bit data.

The Light4 RoboBrick supports RoboBrick Interrupt Protocol for those lines that are being used as inputs. The interrupt pending bit is set whenever the the formula:

L&(~I) | H&I | R&(~P)&I | F&P&(~I)
is non-zero, where: and Once the interrupt pending bit is set, it must be explicitly cleared by the user.

In addition to the common shared commands and the shared interrupt commands, the Light4 RoboBrick supports following commands:
Command Send/
Receive
Byte Value Discussion
7 6 5 4 3 2 1 0
Read Pin Send 0 0 0 0 0 0 b b Read pin bb and respond with 8-bit value vvvvvvvv
Send v v v v v v v v
Read Binary Values Send 0 0 0 0 0 1 0 0 Return the binary values abcd (after XOR'ing with complement mask)
Receive 0 0 0 0 a b c d
Read Raw Binary Send 0 0 0 0 0 1 0 1 Return the raw binary values abcd (no XOR with complement mask)
Receive 0 0 0 0 a b c d
Reset Send 0 0 0 0 0 1 1 0 Reset everything to zero
Read Complement Mask Send 0 0 0 0 1 0 0 0 Return and return the complement mask cccc
Receive 0 0 0 0 c c c c
Read High Mask Send 0 0 0 0 1 0 0 1 Return and return the high mask hhhh
Receive 0 0 0 0 h h h h
Read Low Mask Send 0 0 0 0 1 0 1 0 Return and return the high mask llll
Receive 0 0 0 0 l l l l
Read Raising Mask Send 0 0 0 0 1 0 1 1 Return and return the raising mask rrrr
Receive 0 0 0 0 r r r r
Read Falling Mask Send 0 0 0 0 1 1 0 0 Return and return the falling mask ffff
Receive 0 0 0 0 f f f f
Read High Threshold Send 0 0 0 1 0 0 b b Read and return high threshold for pin bb of hhhhhhhh
Receive h h h h h h h h
Read Low Threshold Send 0 0 0 1 0 1 b b Read and return low threshold for pin bb of llllllll
Receive l l l l l l l l
Set High Threshold Send 0 0 0 1 1 0 b b Set high threshold for pin bb to hhhhhhhh
Send h h h h h h h h
Set Low Threshold Send 0 0 0 1 1 1 b b Set low threshold for pin bb to llllllll
Send l l l l l l l l
Set Complement Mask Send 0 0 1 0 c c c c Set complement mask to cccc
Set High Mask Send 0 1 0 0 h h h h Set high mask to hhhh
Set Low Mask Send 0 1 0 1 l l l l Set low mask to llll
Set Raising Mask Send 0 1 1 0 r r r r Set raising mask to rrrr
Set Falling Mask Send 0 1 1 1 f f f f Set falling mask to ffff
Read Interrupt Bits Send 1 1 1 0 1 1 1 1 Return the interrupt pending bit p and the interrupt enable bit e.
Receive 0 0 0 0 0 0 e p
Set Interrupt Commands Send 1 1 1 1 0 c c c Set Interrupt Command ccc.
Shared Commands Send 1 1 1 1 1 c c c Execute common shared command ccc

3. Hardware

The hardware consists of a circuit schematic and a printed circuit board.

3.1 Circuit Schematic

The schematic for the Light4 RoboBrick is shown below:

Light4 Schematic

The parts list kept in a separate file -- light4.ptl.

3.2 Printed Circuit Board

The printed circuit board files are listed below:

light4_back.png
The solder side layer.
light4_front.png
The component side layer.
light4_artwork.png
The artwork layer.
light4.gbl
The RS-272X "Gerber" back (solder side) layer.
light4.gtl
The RS-272X "Gerber" top (component side) layer.
light4.gal
The RS-272X "Gerber" artwork layer.
light4.drl
The "Excellon" NC drill file.
light4.tol
The "Excellon" tool rack file.

4. Software

The Light4 software is available as one of:

light4.ucl
The µCL source file.
light4.asm
The resulting human readable PIC assembly file.
light4.lst
The resulting human readable PIC listing file.
light4.hex
The resulting Intel® Hex file that can be fed into a PIC programmer.

The Light4 test software is available as one of:

light4_test.ucl
The µCL source file.
light4_test.asm
The resulting human readable PIC assembly file.
light4_test.lst
The resulting human readable PIC listing file.
light4_test.hex
The resulting Intel® Hex file that can be fed into a PIC programmer.

5. Issues

The following issues have come up:


Copyright (c) 2001-2002 by Wayne C. Gramlich. All rights reserved.