These pages are a useful collection of microcontroller RS-232 data acquisition circuits and code. Most of the code on these pages is written in C because it is the language that is definitely the fastest way to produce working applications.

For the people who are interested in these circuits, the code will be available on the pages in C and hex. The hex file code can be cut and pasted into an ascii text file with notepad or another text editor and saved as "name.hex". If there is a problem converting the hex file, please email us and we will send it out! (Not all circuits have micro's or code). 

The pages will be organized as follows:
1). Schematic.
2). C Code.
3). Hex file text.
 

RS232 controlled and RS232 powered DVM-001 voltmeter kit with PC voltage display. This circuit uses a PIC12F675 8-pin microcontroller with built-in analog to digital converter. The circuit also has an op amp and resistor divider network to achieve the 54vdc max input voltage. See the circuit, code and hex file here. Below: circuit board, PC 1st page, PC 2cnd page, board/cables/pickit1, pickit1. Click for larger image.
 

Our reliable relay circuit and code can switch up to 8 independent relays. This inexpensive circuit uses a 18-pin 16C54 microcontroller or any compatible PIC controller (with minor code changes). We have code for Byte Craft and CCS compilers.
In the Byte Craft compiler version 3 C files are provided for the circuit, the main() file and transmit / receive routines. If you will be using the C files, they must be in 3 separate files with the names "relay.c", "rx12.c" and "tx12.c".
Program the chip with Watchdog = off. This code was compiled with MpLab v4.99 and Bytecraft's MPC C compiler v1.31.
In the CCS compiler version there is just one file. The code uses the built-in commands for the RS232 functions. The Watchdog should also be programmed in the off state. MPLab 6.30 and CCS compiler version 3.1 were used for this project.
Use this circuit with the Virtual Relay Control Panel. The VRCP is a windows app that allows you to open and close the relays through your PC by clicking on each relay image. The VCRP project has all the source code to build the app with C++ Builder. The EXE file is included.

Try our FREE v1.0 RS232 C libraries for Hi-tech compilers and Pic 14-bit word microcontrollers including:
PIC12C6XX, 12CE6xx - PIC14000 - PIC16C55x
PIC16C6x, PIC16C6xx, PIC16CE62X, PIC16F62X
PIC16C7X, PIC16C7XX, PIC16F7X - PIC16F8X, PIC16F87X - PIC16C92X
The libraries can be compiled with Hi-tech's PIC or Piclite C (below) compiler's.
Use any/all of the A0-A5 and B0-B7 IO pins for RS232! No need for timers or interrupts! 9600, 19200 or 38400 @ 4mhz.

Build a 4X4 Keypad circuit that transmits an ASCII character on an RS232 line every time a key is pressed. The circuit shown can be used directly from a microcontroller or add the RS232 interface circuit to control the LCD from a PC.
The demo project can be compiled with Hi-tech's PIC or Piclite C  compiler's and our 9600 baud RS232 library.
This circuit uses an inexpensive Grayhill #96BB2-006-F (or similar) 4x4 keypad which can be purchased from Digikey. There are many 4x4 keypads with the same pin-out. Download the project here.

Build a 2X16 RS232 LCD that can be controlled from a PC at RS232 signal levels or from microcontroller levels. The circuit shown can be used directly from a microcontroller or add the RS232 interface circuit to control the LCD from a PC.
The demo project can be compiled with Hi-tech's PIC or Piclite C  compiler's and our 9600 baud RS232 library.
This circuit uses an Optrex DMC-16207U (or similar with 14/16-pin interface) LCD which can be purchased from Digikey for <$20.
Commands include: write char, write string, cursor off, cursor blink, goto line 1, goto line 2, clear.
Download the the project with C files, hex file and lcd.scp script file for RS232 Hex Com Tool 4.0.
(RS232 library must be purchased to compile the project.)

Piclite C compiler for Pic16c84 and Pic16f84 microcontrollers from Hi-tech. The 16f84 is an electrically erasable, 18-pin chip with 1K of flash eprom and 68 bytes of ram. The newest free Piclite compiler can compile code for 8-pin Pic12f675,  Pic12f629, Pic16f627, Pic16f684 and the Pic16f877. We have a copy of the Piclite compiler and the documentation in a self extracting zipped PDF file for download from our server. This compiler can (and should) be used with Microchip's Mplab IDE, here's a link. You'll need a programmer, try the inexpensive, do-it-yourself, Noppp for windows (16f84) or use the Pickit1 proto board and programmer for <$40 (Pic12f675).

RS-232 Virtual DVM circuit, an RS232 powered volt meter, no batteries, no power supplies! The code was compiled with MpLab v4.99 and Bytecraft's MPC C compiler v1.31.
Use this circuit with the DVM2000. The DVM200 is a virtual windows app that shows the voltage at the input to the circuit in a small window on the screen. The DVM2000 project has all the source code to build the app with C++ Builder. The EXE file is included so C++ Builder is not necessary.

Use this generic RS-232 interface circuit to connect a microcontroller to a PC. The maxium chip does the electrical part of interfacing.
The RX and TX lines go to the micro and are wired for a straight through cable. If you have or want to use a null modem cable, simply switch pins 2 and 3 on the DB9 female connector. This circuit uses no handshaking.

Use this RS-232 indicator circuit to monitor the RX and TX line of the circuit above. This circuit uses a 8-pin 12C508 microcontroller, made by Microchip and causes either the TX led or the RX led to turn on for 1/3 of a second when it sees activity on either line. Each led is independent of the other.
Program the chip for Internal Oscillator, MCLR = on, Watchdog = off.
This code was compiled with MpLab and Bytecraft's MPC C compiler.

Download a documentation package to build a in circuit programmer / prototype board for Philips Semiconductors new 8-bit, 8051 compatible, 89C51Rx+ and 89C51Rx2 microcontrollers with up to 64K ISP FLASH and 1K RAM. This board can be used for other purposes by using the expansion connectors. You can build this board for around $50.

Sometimes it is necessary to isolate the peripheral circuit from the PC for noise or floating ground situations. This circuit will do the job. The circuit uses a DC/DC converter made by Power One, Inc. These parts can be purchased from Digikey.

A very good C compiler with a good reputation. Comes with examples and built in functions.
Write code for ALL microchip devices for under $500.00 or for most of the micro's on this page for $125.

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