Paul's 8051 Tools, Projects and Free Code

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AS31 Assembler & SDCC C Compiler

SDCC is a free C compiler written by Sandeep Dutta, Micheal Hope, Alan Baldwin, John Hartman, Dmitry S. Obukhov, Jans J Boehm, Alan J Demers, Jean Loius-VERN, Daniel Drotos, Kevin Vigor, Johan Knol, Scott Dattalo, Karl Bongers, and others. More details are available at the official SDCC web site. The SDCC available here, with "-pj#" added to the version number, is a modified version that includes some additions to better support the 8051 developement boards available at this site.

GNU Make is written by Richard Stallman and Roland McGrath, as part of the Free Software Foundation's GNU's Not Unix project.

	Linux Download and Installation Instructions

• AS31 2.0beta3 Source Code (82k download)
• SDCC 2.3.1-pj2 Source Code (2.8M download)
• Compiling AS31 and SDCC on Red Hat 7.1 with gcc 2.96.

	Windows Download and Installation Instructions

• SDCC C Compiler and AS31 Assembler and GNU Make Win32 Binaries (1.1M download)
• Installing AS31, SDCC and GNU Make Binary Package

SDCC and GNU Make are Free Software provided under the GNU General Public License (GPL). AS31 is also Free Software, provided under the BSD license. The standard C libraries provided with SDCC are covered by the terms and conditions of the GNU Lesser General Public License (LGPL).

SDCC, AS31, and Gnu Make are distributed in the hope that they will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.

A copy of the old as31 page is still available.

PAULMON 8051 Family Monitor/Debugger

• Download PAULMON2
• Read on-line Documentation for PAULMON2
• The original version is still available.

PAULMON is a user-friendly 8051 family monitor, intended for use in a single board computer like the development board below. By placing PAULMON in the board's EPROM, the board will "boot-up" to a friendly menu-driven monitor which allows you to download your programs to RAM and run them, which is much faster and easier than reprogramming the EPROM. PAULMON also provides several features to help you debug your programs, including a disassembler and single-step program execution.

It is very easy to use and together with an 8051 family assembler, such as the one above, it provides a very low-cost 8051 development system. PAULMON is in the public domain. You may use pieces of the code in your own programs and even incorporate the code into your own commercial products, if you wish.

Download PAULMON2 Source or Object Code. Nearly everything is improved and several new features have been added... generally much better than version 1, even in the beta versions. Documentation for PAULMON2 is available on-line.

PAULMON1 was originally developed in the Fall of 1991 in about four weeks. The code has remained fixed, but my own needs have changed from project to project over the years. These changes, additional features, plus a major overhaul of the existing code is finally available as PAULMON2.

Low-Cost 8051 Development Board Design

• Features and Photos
• Using The Board For The First Time
• LED Blink Example, Using AS31 Assembler
• LED Blink Example, Using SDCC C Compiler
• Memory Map
• Schematic and Parts List
• PC Board Details
• Construction and Testing
• Troubleshooting Tips

Figure 1: 8051 Development Board, Rev 4, With 16x2 LCD

Important Features:

• PAULMON2 v2.1 Monitor, easy to learn and use. All PAULMON2 source code is available for free download, and may be used without any restrictions, even for copy-and-paste into your own programs.
• Flash ROM for non-volatile storage of downloaded programs, to allow the board to permanently run the downloaded program, without the PC computer. No EPROM programmer is needed to make the board permanently run your application. The Flash ROM can also be used for data logging.
• Two serial port connectors w/ on-board mux, allowing easier development of applications which require the serial port
• 32 I/O Signals, and 8 Bit Bus signals, clearly labeled on the board
• Large prototype area to add custom circuits

The older versions are still on line: Rev 3 (2001) Rev 2 (1997), and Rev 1 (1992). Parts for these boards are no longer available.

8051 Code Library

These 8051 code examples are distributed in the hope that they will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.

Paul's Code Library

• Serial I/O Routines
• Automatic Baud Rate Detection
• Interrupt Driven Serial I/O
• Fixed-String Lexer
• Pseudo-Random Number Generators
• Serial EEPROM (93C46/93CS46) Read, Write, etc
• AMD Flash ROM Program and Erase Routines -- incomplete
• Xilinx FPGA Configuration Programming -- incomplete
• Using the 82C55 chip
• Interfacing with an IDE Hard Disk Drive

Contributed Works

• Tiny Basic For 8051 ported to PM2 by Dave LeBlanc.
• LCD Display Routines and a simple schematic by Dzidek & Ogest.
• LCD Display via 82C55 by Ben Loveday.
• LCD Display Driver by Ho Weng San
• Xilinx Download and readback for XC3090 by Craig Jackson
• Misc code library by Stephan Joubert also in a ZIP file.
• AT89C2051 programmer, the code is in this ZIP file by Paul Hoepping

Atmel 89C2051 in-circuit programmer

I have designed and built a simple programmer for this cool part which can reprogram it in-circuit. You place the 89C2051 in this board, and connect the board to your project's 20 pin socket with a ribbon cable. You can download code to the programmer, reprogram the Atmel chip, and then place the chip back into the circuit. Since it's Flash ROM, no UV erase step is required. You can reprogram and test your code without moving the chip between sockets. As well, the programmer supports an "echo-thru" mode, where the 89C2051's UART output is echoed to the terminal controlling the 89C2051 in-circuit programmer, but only while the 89C2051 is running in-circuit.

To get started now, the design is quite similar to the development board example above, with the addition of the following chips: 74HC00, CD4007, and four CD4066. The three unused AND gates in that example are used here. Two NPN and one PNP small-signal transistors are needed, as well as a 12 volt power supply for the programming voltage and 4000 series logic. Only one of the 82C55's is used, but one 82C55 is required. BETA Version 0.004 is now available, also in ZIP format. As well, BETA Version 0.003 is still available, but 0.004 is much easier to use.

Someday more reasonable documentation and a schematic of the required hardware will appear. For now, this beta release schematic is available for those who want to try to add the hardware support to an existing development board.

Other Resources

• Free Stuff on the Net
• Manufacturer's 8051 Datasheets
• Commercial Products