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HP-41 Hardware Interface Activities

Posted by Klug Christoph on 2 Apr 2000, 9:22 p.m.

Also today I like working with the *nostalgic* Fourty-One handheld computer system. From this activities results a collection of HP-41 and HP-IL components. My activities are concentrated to the powerfully CX model, belonging software development includes User code and synthetic programming, not mcode programming. For realizing extensive software solutions I work with RSU (Ram Storage Unit) and burn own ZEPROM-Modules (EPROM).

Main subject is interfacing of external electronic hardware to HP-41 handheld by using HP-IL and HP 82166A IL-Converter. For realizing this I create two systems : First I developed the battery powered, modular Input/Output-Board for use with the IL-Converter. The I/O-Board manual in English language (16 chapters and over 300 pages) contains some analog- and digital-circuits for *measurement and control applications*. Both, HP-41 and I/O-Board creating an expandable software/hardware system for realizing individual applications. The second solution is the IL2000 System. This brings complete I/O-Board technology plus some extended features into a small, handy box, working with surface mounted parts. For the belonging English language IL2000 manual (up to now 3 parts and 100 pages) further updates are planned.

Connecting HP-41 to I/O-Board or IL2000 System make possible data logging applications. For processing measurement-data the transfer to modern PC have a key function for today work with HP-41. By using HP-IL with an own rebuild version of the HP-IL * PC Interface Card I merge mobile HP-41 system and modern PC. Existing transfer software solutions like LINK PLUS or TRANS41 are tested and improved for usage with HP-41.

Above activities completed by writing HP-41 articles as author for the Datafile Journal, published world wide for members of the HPCC Handheld and Portable Computer Club (London).

The collection of HP-41 parts and accessories, HP-IL devices and books and software is an by-product of using HP-41. By trading components with other handheld computer fans I hope to improve existing stock of my collection.

Also for today work the *nostalgic* HP-41 is a powerful handheld computer system : With additionally plug in expansion modules you bypass hardware limitations. And by using HP-IL you realize extensive data storage, printing, plotting, interfacing, measurement and data-transfer to PC.

*HP-41 Hardware Interface Activities* also includes support of today business of HP-41 users, fans and handheld computer collectors, like trading tools and parts, or exchanging software and books. Please contact :

Christoph Klug Körnerstraße 47 B 31141 Hildesheim Germany

HP-41 Input/Output-Board:

Interfacing extern measurement and control hardware to HP-41 handheld computer using the HP 82166A IL-Converter.

by Christoph Klug

Most people use the HP 82166 A IL-Converter to adapt a standard parallel printer to HP Interface Loop. Alternatively you can use the powerful IL-Converter to connect electronic hardware to the Interface Loop, controlled by the HP-41 handheld computer. I developed an Input/Output Board for the HP 82166 A IL-Converter, designed as a mainboard with four 16 bit extension slots.

HP-41 Interface Loop Controller :

Best HP-41 IL-Controller is the powerful CX model with intern X-Functions, X-Memory and Time-Module. Additionally you need the HP 82160 IL-Module plus EXT I/O-Module to control the Interface Loop. Instead of EXT I/O-Module you can use the Development-Module. For maximum performance you can complete the handheld with the German CCD-Module. Hard- and software of I/O-Board are developed to work optimal in combination with other Loop-Devices like Cassette Drive, Thermal Printer or Video Interface. For that reason you can configurate extensive IL-Systems.

Software for EXT I/O-Module and Development-Module :

For controlling I/O-Board with HP-41 you must alter some internal status register of the HP 82166 A IL-Converter. Therefore you need the EXT I/O-Module or alternatively the Development-Module. For EXT I/O-Module 695 Bytes (= 100 Registers) of software programmed for the HP-41 to control I/O-Board, or 811 Bytes (= 116 Registers) of software for Development-Module.

I/O-Board Software for EXT I/O-Module :

Controlling the I/O-Board with HP-41 CX and EXT I/O-Module is easier and faster than with Development-Module ! The I/O-Module uses the ALPHA-Register to transfer data to IL-Converter. Avoiding problems with loss of leading null bytes in ALPHA-Register, EXT I/O-Module generally works with leading dummy byte D. For controlling the I/O-Board with HP-41 CX and EXT I/O-Module, 24 commands are provided for power up/down, initialisation, addressing, manual service request, interrupt, clear, 16-bit I/O-transfer by ALPHA-Register and by X-Register and 8 bit I/O-transfer by X-Register. For 8 bit I/O-transfer the software provided needs the X-Memory Module for storage.

I/O-Board Software for Development-Module :

Controlling I/O-Board with HP-41 CX and Development-Module is more complex and slower than with I/O-Module ! The Development-Module generates a Buffer to transfer data to IL-Converter. An advantageous feature of the Development-Module is the INTR-routine, which starts HP-41 automatically from an active MSRQ-signal ! For controlling the I/O-Board with HP-41 CX and Development-Module, 22 commands are provided for power up/down, addressing + initialisation, manual service request, interrupt, clear, 16-bit I/O-transfer by X-Register and by ALPHA-Register, 8 bit I/O-transfer by X-Register.

I/O-Board and Time-Module :

You can use Time Module commands for automatic control of I/O-Board. For example power up the system using an alarm function and start some activities like measurement, storing data in main memory or cassette drive, then set new time alarm and put the I/O-Board to sleep waiting for next cycle.

I/O-Board and CCD-Module :

For controlling I/O-Board you do not require the German CCD-Module, but this helpful module expands HP-41 with 100 powerful commands programmed in machine-language. Some are fantastic for use with I/O-Board and make work easy : Synthetic programming, binary-functions for logic bit operations, matrix- functions for data collection applications.

I/O-Board and Zeprom-Module :

The Zeprom-Module is a EPROM housed in a HP-41 plug in modul case, produced by Zengrange (London) who also produced the well known HP-41 Zenrom-Module. Permanent storing complete I/O-Board control command set inside Zeprom is done by adapting module to small plug in burning converter tool and using corresponding Programer-Rom software. Using Zeprom-Module, HP-41 main memory is complete free for other program applications and I/O-Board software is protected against memory lost. 51 commands controlling I/O-Board plus 12 utility functions now belonging to CAT 2 and assigned to three User keyboards, which selected by softkeys. Zeprom-Module sum up extension modules and I/O-Board software in only one HP-41 plug in port.

Extern Interrupt :

Inside HP-41 case you can mount a small hardware extension circuit for switching handheld computer from sleep-modus to run-modus by extern interrupt signal. As response to extern event HP-41 starts automatic control of I/O-Board. Because interrupt circuit works with an opto-coupler element there is no risk for damanging HP-41 ! During a running program extern interrupt signal can not switch off handheld computer.

HP-41 and PC :

Normally I/O-Board data processing is done completely by HP-41. But it is possible to transfer HP-41 data-files to a PC. Use a HP-IL * PC Interface Card and Link Plus or Trans41 software. Link Plus only runs on 286/16 MHz PC´s and on slow 386SX/25 MHz PC´s and emulates two Cassette Drives, a Video Display, a Printer and a DOS file. Trans41 runs on modern PC´s and emulates a Printer, a Cassette Drive and a DOS file. Collect data by HP-41 and I/O-Board in the field. Now transfer HP-41 data-files to PC and DOS area. Than import data to EXCEL or other powerful software package for post processing.

I/O-Board Hardware Feature List :

The board uses a basic application for handshake timing from Gary Friedman, described in his book "Control The World With HP-IL". Some more helpful circuits added to the board to improve I/O performance. You find hardware solutions for port addressing, Power On reset, MSRQ (Manual Service Request), Clear function, Power Up/Down function, MSRQ Lock when Power Down and a Reference Voltage. Power supply is external : A special 6V DC-supply unit with optional solar powered rechargeable cell for modular applications. Output voltages are +5V and + 15V for digital- and analog circuits. Stand by current of DC-supply (Power Down) is lower than 10 mA !

I/O-Board Port Configuration :

The I/O-Board supports four 16 Bit slots. Every slot is divided into two 8 Bit ports A and B. All slots are connected by a common bus with power supply, handshake lines and data lines. The logic of I/O-Board hardware maximally addresses two 16 Bit input modules and two 16 Bit output modules plugged in at same time ! Address setting is done by jumpers on the modules, not by slot position. Inserted 8 Bit modules need additional software addressing. The slot architecture of the board, hardware and software addressing allows some port configurations for digital and analog input/output.

I/O-Board Plug In Modules :

I/O-Board uses 8 bit or 16 bit add-on modules. On next page is the list of the basic modules for completing motherboard hardware. Furthermore some special modules exist like analog filter modules an RMS measurement module or a computer controlled sine wave generator module. The modular hardware concept of the I/O-Board makes it possible to configurate the interface system with I/O ports to every task you want. You can also develop special modules for your own applications and hardware projects. The I/O-Board is a good basic IL-Device to implement your ideas quickly !

-8 Bit digital input modules and opto isolated input modules. -8 Bit digital output modules, opto isolated output modules and open collector output modules. -8 Bit analog digital converter modules and 8 Bit digital analog converter modules. -12 Bit analog digital converter modules and 12 Bit digital analog converter modules. -16 Bit counter modules. -Quad Multiplexer modules. -Transfer modules for data exchange between two I/O-Boards. -Diagnose modules and Test modules. -16 Bit digital controlled sine-wave generator module. -RMS Converter module (AC millivolt measurement)

Quality Tests :

Correct and bug free function of software and interface hardware tested with some HP-41 Controllers, some IL-Converters, and eight samples of the I/O-Board which I have built ! Measurement tools and software programs for testing mother board hardware and plug in module circuits exist.

I/O-Board Manual :

The English language manual for I/O-Board (16 chapters and over 300 pages) includes circuit descriptions, circuit diagrams and software documentation for HP-41 CX including barcode plots. The manual is a rich source for users, who want to use the IL-Converter in their own electronic equipment, and for those, who want to learn step by step something about interface technology (read and write bytes to external hardware devices, voltage conversation to the analog area). Test programs included for checking hardware functions. Some practical tips for building, installing and starting with I/O-Board complete the manual, including advanced programming tips and reference lists.

Furthermore manual includes a program for printing HP-41 barcodes on HP DeskJet 500 printer. This needs an HP-41 with HP-IL module, Extended Functions (on a plug-in module or built into an HP-41CX), a CCD-Module plus an HP 82166A IL-Converter to connect the DeskJet 500, or an HP-IL PC interface card to print the barcodes to a printer connected to a PC.

Also manual contains information about HP-41 hardware modifications like building Double X-Memory Modules, interrupt circuit for waking up handheld by extern signal and a extern battery power supply unit. Own chapters describe burning Zeprom-Modules and realizing data transfer or upload from handheld to PC by using the HP-IL*PC Interface Card with Link Plus or Trans41 PC software and improved HP-41 software for transfer main memory register-blocks, X-Memory data- or ASCII files or CCD-Module matrix files to DOS files.

For giving the reader an practical application and imagination about flexibility and amazing performance of HP-41 & HP-IL & I/O-Board one chapter contains the complete hardware and software solution for realizing audio frequency response measurement, including advanced data processing by working with CCD-module matrix files, data storage by X-Memory and Cassette Drive, data output by IL-Printer and IL-Plotter and data transfer to PC !

The manual is completed by a HP-41 & HP-IL reference list, a photo-story about history of developing I/O-Board system and some more photos and details about IL-Devices for measurement, printing&plotting and data-storage. The manual is written for use with I/O-Board, but the manual can be read on it´s own for the details and programs it gives. Describing the advanced development, manual continues Gary Friedman´s book *Control The World With HP-IL*.

Source of Equipment :

The HP 82166 A IL-Converter is the key part for I/O-Board. Some kits for building this unit including IL-Terminal, IL-Transformer and IL-Chip exist. Printed circuit boards exist for the I/O-Board but presently with only single-sided layout. You must make a lot of additional connections in wire wrapping or soldering technique. That is easy for electronic professionals. For people who have no complex measurement equipment I can align some critical components. Electronic novices can get a completely finished and tested version of I/O-Board including DC Power Supply. Building plug in modules for I/O-Board is not complex and can done by newcomers to electronic construction.

Conclusion :

Today the HP-41 is a nostalgic handheld computer. With added accessories like plug in expansion modules you can bypass hardware limitations of the system. Using the IL-Converter and I/O-Board you open up the interesting field of controlling and developing external hardware. Now you can realize measurement and control from your HP-41, a task normally done with larger systems. Interfacing the handheld to modern PC you can also use modern software tools to analyse the data.

For more information about HP-41, HP 82166A IL-Converter, Input/Output Board and belonging I/O-Board manual write to :

Christoph Klug Körnerstraße 47 B 31141 Hildesheim Germany

I/O-Board Manual Contents :

CHAPTER I Introduction


CHAPTER III I/O-Board Hardware



CHAPTER VI Practical tips


CHAPTER IIX References






CHAPTER XIV I/O-Board Data Transfer

CHAPTER XV HP-41*PC Data Transfer


IL2000 Interface System :

Connecting HP-41 & HP-IL Interface Loop to Future :

by Christoph Klug

When I start 1980 using HP-41 handheld computer, I don´t know that this nice machine fascinates me up to 20 years later ! From this work results some special software like a 8 kByte solution for acoustics and loudspeaker development. But most fun I get by interfacing external hardware to the handheld, using the HP 82166A IL-Converter. Some articles about this I/O-Board project are published in former HPCC Datafile Journals. During this two decades I have nice contacts and exchange with other HP-41 enthusiasts and fans world wide !

The existing modular hardware system of I/O-Board (IL-Converter, motherboard, power supply board, lead cell battery, some different plug in modules ...) is ideally for use on workbench, for evaluation and prototyping interface solutions for measurement and control hardware applications with HP-41 handheld computer system. But for mobile and portable applications the I/O-Board system do not have a practical housing like a closed case or a handy box. Furthermore producing of I/O-Board and belonging Power-Supply unit is a mixture of working with printed boards plus additionally hand wiring much lines and components. To overcome this wake points, now I start the IL2000 project :

New Interface Hardware :

By working with surface mounted components, IL2000 project transfers complete proved I/O-Board technology into a handy box. Some interface- and power supply features expanded : Addressing maximally 8 sixteen bit I/O ports (I/O-Board addresses only 2 sixteen bit I/O ports), a three colour diagnostic LED, some optional supply voltages, a solar cell charger option and a low bat indicator circuit. The new modular mechanical design is realized by 10 inch rack case parts. Some parts are modified for reaching standard height of only 88mm. For extensive interface applications, mounting more hardware modules is possible by enlarging box width up to 19 inch rack size.

IL2000 interface board + IL-Converter + POW2000 power supply board stacked together, forming the basic hardware module, placed to right side of 10 inch rack case. A 50 pin flat ribbon wire power- and data bus is connected to additionally plug in modules : I/O2000 is the adapter solution for employing proved I/O-Board plug in module family. Inserting two 16 Bit or four 8 Bit plug in modules is possible. DIG2000 board make possible general 16 Bit digital I/O applications. Additional evaluation area including a ground-plane gives you some space for placing own hardware circuit extensions.

HP-41 software used for IL2000 system is compatible to I/O-Board. Refer to I/O-Board manual Chapter II and Chapter VII . Addressing additional input- and output ports needs expanded software. Like I/O-Board also IL2000 interface board works with pulsed GETO-Line (IL-Converter trigger signal) for port addressing.

IL2000 system is the multi-purpose interface solution for expanding HP-41 handheld computer system by advanced input/output applications. The portable, battery powered design is helpfully for today HP-41 fans and enthusiasts, and for electronic professionals. The modular hardware concept make possible configuration of IL2000 interface system to every task you want. Developing special modules for you own applications and hardware projects is possible in short time. IL2000 system continues proved I/O-Board design, and both systems are fantastic IL-Devices for implementing your ideas quickly !

IL2000 Manual :

New IL2000 interface system is documented by an own manual. This complements the existing 300 page I/O-Board manual. Like the history of growing I/O-Board manual also for IL2000 manual future updates are possible, describing more hardware applications and system expansions. The first print of IL2000 manual includes some photos, diagrams and more than 100 pages. First chapter contains prefaces, written by the handheld computer book authors Gary Friedman (Control The World with HP-IL), Dr. Tony Duell (HP-48 I2C-Bus Interface) and Wlodek Mier-Jedrzejowicz (Extend your HP-41). Second chapter describes the complete hardware and the mechanical design. Third chapter gives a first example working with IL2000 system : Third octave frequency response audio measurement. This application continues audio measurement chapter XVI of I/O-Board manual. For getting a own sample of the new IL2000 manual contact the author.

For more information about HP-41, HP 82166A IL-Converter, IL2000 System and belonging IL2000 manual write to :

Christoph Klug Körnerstraße 47 B 31141 Hildesheim Germany

IL2000 Manual Contents :

PART I Prefaces from Gary Friedman, Christoph Klug,

Dr. Tony Duell and Wlodek Mier-Jedrzejowicz

PART II Connecting HP-IL Interface Loop to Future

PART III Audio Third Octave Frequency Response Measurement

Audio Measurement with HP-41 :

by Christoph Klug

The HP-IL Interface Specification 82166-90017 describes a scenario for realizing audio measurement with HP-IL : The application use the HP-85 Personal Computer, controlling the HP 3468A IL-Digital Multimeter for measurement of AC voltage levels. Additional HP 82166A IL-Converter is interfaced to a Multiplexer-Device for connecting Digital-Multimeter to different points of measurement object, controlled by software.

Today the modular, battery powered I/O-Board make possible similar measurement application with minimal hardware expense. Chapter XVI of I/O-board manual contains detailed informations : By using modern analog IC´s we expand the existing I/O-Board plug in module family by two special modules. The Micro Linear ML2038CP is a one chip sine-wave-generator (internal wave-table-rom and 8 Bit DAC), controlled by parallel 16 Bit data word. And for measuring AC voltage levels we take the SSM2110 RMS-Log-Converter chip (from Analog Devices) as frontend for the existing 12 Bit ADC-Module.

The rest is done by software : For HP-41 we program control routines for setting frequency of sine-wave-generator, and for reading voltage level to X-Register. Working with high accuracy reference measurement equipment during calibration (Rhode & Schwarz Audio Analyzer UPA 3) and using curve fitting routines (HP-41 AEC-Rom) our low cost system reach amazing performance : Generator frequency runs from 5Hz to 60KHz with 1Hz resolution. Measurement of AC voltage levels runs from -80dB (=0,1mVeff) to +20dB (=10Veff), typically accuracy is +0,3dB !

For determining the complete frequency response (for example of a Hifi-Device) we need additional software. By entering start- stop- and increment-frequency we execute an automatic measurement sequence. Voltage level readings may be stored in X-Memory data-files. But much better is working with CCD-Module matrix-files. A measurement sequence creates two matrix-files, one for parameters (name, date, time, start- stop- increment-values ...), belonging second matrix-file containing measurement data (AC voltage levels).

By using CCD-Module math-matrix commands we program a helpfully math-function set for calculating frequency response data : Invers frequency response, adding frequency response data, shifting, finding max peak, smoothing (for acoustical measurement). For completing this audio-measurement system we add some HP-IL Devices : IL-Cass-Drive for extensive data storage, IL-Printer and IL-Plotter for data output. Using HP-IL*PC Interface Card, we transfer measurement data to PC, making possible data post processing with EXCEL.

Part III of IL2000 manual continues chapter XVI of I/O-Board manual and describes additional HP-41 software for carrying out third octave frequency response measurement. Additional software make possible Multi-Plots using IL-Plotter. Furthermore some optional hardware extensions given like adapting a microphone for acoustical measurement or an expanded input multiplexer section with high impedance line level input, 10KW input, 16W input and a balanced input.

For more informations about using HP-41 for Audio Measurement write to :

Christoph Klug Körnerstraße 47 B 31141 Hildesheim Germany


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