This is the revision D version of the Shaft2 module.

Shaft2 Module (Revision D)

Table of Contents

• 1. Introduction
• 2. Programming
• 3. Hardware
  • 3.1 Circuit Schematic
  • 3.2 Printed Circuit Board
• 4. Software
• 5. Issues
• 6. Additional Information

1. Introduction

The Shaft2 module keeps track of two quadrature rotation sensors.

2. Programming

Command Name	Action	Bit									Description
		8	7	6	5	4	3	2	1	0
Count Latch	Send	0	0	0	0	0	0	0	0	0	Latch the current rotation count for both shafts.
Count Clear	Send	0	0	0	0	0	0	0	0	1	Clear rotation count for both shafts.
Shaft High Get	Send	0	0	0	0	0	0	0	1	s	Read the latched 16-bit shaft value for shaft s. Return the high order 8 bits as hhhh hhhh. Save the low order 8 bits for the Shaft Low Get command.
	Receive	0	h	h	h	h	h	h	h	h
Shaft Low Get	Send	0	0	0	0	0	0	1	0	0	Return the low order 8 bits of the last shaft read as llll llll.
	Receive	0	l	l	l	l	l	l	l	l
Common Commands	Send	0	1	1	1	1	1	x	x	x	Standard common command. See specifications for details.
	Receive	0	a	a	a	a	a	a	a	a
Select	Send	1	a	a	a	a	a	a	a	a	Select the module with an address of aaaa aaaa. A time-out indicates that the module is not selected.
	Receive	0	1	0	1	0	0	1	0	1

3. Hardware

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

3.1 Circuit Schematic

The parts list kept in a separate file -- shaft2.ptl.

The schematic for the Shaft2 module is shown below:

3.2 Printed Circuit Board

The printed circuit board files are listed below:

shaft2_back.png

The solder side layer.

shaft2_front.png

The component side layer.

shaft2_artwork.png

The artwork layer.

shaft2.gbl

The RS-274X "Gerber" back (solder side) layer.

shaft2.gtl

The RS-274X "Gerber" top (component side) layer.

shaft2.gal

The RS-274X "Gerber" artwork layer.

shaft2.gml

The RS-274X "Gerber" mask layer.

shaft2.drl

The "Excellon" NC drill file.

shaft2.tol

The "Excellon" tool rack file.

4. Software

The following files are available:

shaft2.ucl

The Shaft2 µCL source code file.

shaft2.asm

The Shaft2 firmware assembly code listing.

shaft2.lst

The Shaft2 firmware listing file.

shaft2.hex

The Shaft2 firmware Intel^® Hex file.

5. Issues

The following fabrication issues came up:

• In order to support the changing of module addresses, it is necessary to use a device that has an EEPROM. The PIC16F767 does not qualify, but the PIC16F876A does. The PIC16F876A needs to have pin 1 tied to +5 volts.

6. Additional Information

The motors and shaft encoders that have been used with this module come from Solutions Cubed. In particular, the motor is the MOTOR1 and the encoder is the ENC300. The motor is available from alternate vendors such as Jameco. The encoders are actually from US Digital. The nice thing about Solutions Cubed is that they sell the motor, encoder, and encoder mounting kit all together, so there is no finger pointing if parts are missing.

The shaft encoder chip is the LS7366 from LSI Computer Systems and it is very difficult to obtain. I eventually wound up buying a tube of the chips from Gemini Electronics. When I called them I had to ask if they sold the chip, since it was not listed on their web site.

The encoders from US Digital conform to the following pin outs.

Pin	Usage
1	Ground
2	Index
3	A Channel
4	+5 Volts
5	B Channel