AVR Microcontroller

Wireless Coupler Terminal Interface

The purpose of the terminal interface is to allow my computer to communicate with Minimum Mass Wireless Coupler equipped devices using a terminal emulator program. Consequently, the Base Unit is basically an RS-232 interface and Minimum Mass Wireless Coupler. The Base Unit is the larger enclosure in Photo 1. The RS-232 interface to the computer is 9600 baud, 1 stop bit, no parity, plenty fast to keep up with the 1200 baud maximum data rate from the Coupler. The antenna is made of 12 turns of #30 enameled wire threaded through metal guide loops arranged around the perimeter of the board (See the photograph.) This antenna's area is about 160% that of the prototype 5.5 cm loop so it has a little more range for both transmitting and receiving. ..

Wireless Coupled Scanning Voltmeter (ATMega8)

A 10 bit scanning voltmeter with a Minimum Mass Wireless Coupler, based on the ATMega8.Range to the Minimum Mass Base Unit is 10 to 15 cm. If the voltmeter is battery operated, it can be floated from ground. This project is very simple physically, intended to demonstrate how easily the Minimum Mass RF Link can be added to a project. The circuit shown does not have a lot if the nice things that I would usually include in an instrument, such as the ability to handle out-of-range input signals without the circuit suffering damage. Therefore, I suggest that if you build this as a stand-alone instrument, that you add protection crcuitry to the inputs. The basic Minimum Mass Wireless Coupler technology is described and links to other projects on this site that use the Minimum Mass Wireless Coupler are located on the web page, Minimum Mass Wireless Coupler. ..

Wide Basic for ATtiny2313

This firmware is intended to run on an Atmel ATtiny2313 operating from a 4, 8, 10, 16, or 20 MHz clock or an AT90S2313 operating from a 4 MHz clock. As far as I have been able to determine, the ATtiny2313 and AT90S2313 versions are interchangeable, and the only difference is that they were assembled using different include files. When connected to minimal interface circuitry, a chip programmed with this interpreter will interact with an ASCII terminal allowing the writing and execution of small Basic programs and hardware debugging by immediately executing commands from the terminal that are not preceded by a line number. Communications with the terminal is via RS-232 (EIA-232) at 9600 baud, 8 data bits, one stop, no parity. Pin 2 (RXD) and pin 3 (TXD) should be connected to an inverting RS-232 interface as shown in the schematic on this page. The Maxim MAX-232 and similar interface chips as well as the discreet interface shown in Atmel's AVR-910 application note are examples of such interfaces...

Frequency Meter

This basically the frequency meter section of the frequency meter/pulse generator based on the AT90S2313 described elsewhere on this site, combined with the 100 MHz RF interface described in the page about the RS-232 to 100 MHz RF desktop channel adapter. Built and align this is the same manner as the 100 MHz RF desktop channel adapter. The frequency meter has a maximum input frequency of 4 Mhz and counts up to 65535. Time bases of 10 ms, 100 ms, 1 second, 10 seconds, and 100 seconds are selectable from the keyboard via the RF link...

This section describes an experimental low power, low bandwidth data signaling system that was initially made to operate at 55 MHz (television channel 2 in the U.S.). Before operating a radio transmitter, find out what kind of transmitter operation, if any, is permitted in your locality. Radio transmitter operation is a serious legal matter. This design can be readily adapted to different frequencies and lower power levels. If you choose to build and operate the transmitter described here, you do so at your own risk. I'm only publishing this as an example of what can be done, and to show how easy it is to build a simple but functional receiver...

Data Transfer interface

The DS protocol was designed to provide firmware-based bidirectional host-to-slave inter processor communications for situations in which no hardware solution is available and the host and/or the slave in incapable of tending the interface in real time. The only specialized hardware required is two bidirectional I/O ports on each chip (alternatively two input ports and two tri-statable output ports may be used. In other words, it provides some of the functionalit of the Two-Wire-Interface (TWI, or I2C as named by Philips) where an actual TWI is not feasible in either hardware or firmware...

Clock/Calendar/Alarm with ATtiny12

This is the timekeeping test circuit. It includes a one-transistor circuit to switch in the 5V power supply when present and drop back to the 3v battery the rest of the time. That loop of blue wire-wrapping wire is a lariat used to quickly and easily pull the chip out of the socket during development without damage and without having to reach for the removal tool. Low current operation (chip sleeps most of the time). Alarm and external event triggered interpreter operation. Capable of stand-alone timer and alarm use. No additional processor required once programmed. One external input pin and one open drain output pin for interpreter...

Serial Programmer for AVR microprocessors

Atmel described a simple programmer based on the AT90S1200 (NOT the AT90S1200A) controller in their application note, AVR910 (a modification to use the AT90S2313 is also given below).The circuit is so small and simple, I was able to put two of them together without using a printed circuit board, taking only about an hour to assemble each one. Both worked fine without any hitches. These programmers are compatible with RS-232 ports, cost well under US$10 to build, and program AVR chips in the serial mode (and thus is not able to access programming options only available in parallel mode -read those data sheets!). It connects to a target controller via a 6 pin cable. ..

330 MHz Remote Control ATTINY2313

Once the transmitter circuit was working well, all that was left was to add an ATTINY2313, a battery, and some buttons. The Princeton Technology decoders, such as the PT2272, have an amazing tolerance for data rates - about plus or minus 50%. The ATTINY213 is clocked by its internal RC oscillator, and given the wide tolerance of the decoder, I didn't bother to calibrate the oscillator. The five input pins are configured as inputs with internal pullup resistors and the pin change interrupt, set to interrupt when the pin makes a high to low transition, is enabled for each input...

AVR FM Stereo Transmitter

A composite stereo signal, as transmitted by FM radio stations, is composed of at least three parts: A base band mono signal, a double sideband channel difference signal, and a pilot carrier. The signal composition is somewhat analogous to an NTSC composite color television signal. I said "at least three parts" because some stations transmit other things such as data and background music that our normal FM receivers do not decode. The base band signal falls between 30 Hz and 15 kHz. This is the part of the audio signal that comes out of the speaker on a mono receiver, In the classical encoder, it is made by simply adding the Left and Right channel audio signals together, and is often referred to as "L+R."..

AVR Microcontrolled PLL FM Transmitter

An LMX1601 Phase locked loop, a discreet FET VCO, and an AVR micro controller combine to make a stable, easy to use monophonic FM transmitter that includes a an audio activated switch that turns the transmitter on only when its being used. The common characteristic of all of the previous low power FM transmitters I've built over the decades, is that their operating frequency is determined by an LC resonant circuit. Some of them had excellent stability, some of them didn't, but I had always wanted to make one that is crystal controlled. ..

AttoBasic

This firmware is intended to run on Atmel ATmega163 (499 bytes for program memory) or AT90S8515 (298 Bytes for program memory). Communications with the terminal is via RS-232 at 9600 baud. Use 8 data bits, 1 stop bit, and no parity. The RXD pin and TXD pin should be connected to an inverting RS-232 interface. The Maxim MAX-232 and the discreet interface shown in the schematic which is described in Atmel Application note AVR-910, are examples of such interfaces. If the RXD pin is grounded when the chip comes out of reset, either from application of power or after an external reset, the contents of the EEPROM will be loaded and executed by the interpreter. ..

Programable Board with 32K RAM

While there is a list of features that I would like to add (32k EEPROM support, line numbers to 65,535, more stack space, strings, arrays, 16 bit variables and arithmatic, possibly named variables and REM statements for starters), I have not been able to dedicate much time to this project. You are invited to make enhancements, and I sure would like a copy if you make any enhancements. This is the current stat of a work in progress, though progress may be slow, I've modified the program memory to use 32k bytes of external RAM. I used a Cypress CY7C199-150, though other 32K static RAMs can be uses as well. Just make sure to check the Write and Read pulse polarity on the alternate chip. ..

RF Field Strength Probe

This broadband probe has a small antenna (about a 15 cm length of insulated wire). Radio Frequency energy coupled to the antenna is detected and made available to drive millivolt level signals to the input of a DVM (Digital Volt Meter). Its battery powered for convenience with very low current drain and automatic shutdown for long battery life. I've used the circuit shown below to check the output of transmitters at 4 MHz, 35 MHz, 55 MHz, 100 MHz, 900 MHz, a cell phone, and a microwave oven. It really is broad band, though I don't make any claims for the flatness of response. Since the collectors and emitters of the detector transistor are both at RF ground, choice of transistors isn't all that critical. ..

89Sxx Development Board

The hardware block is shown in Figure 1. The MCU is 89Sxx microcontroller. And the complete hardware schematic is shown in Figure 2. Port1 is used as data-bus for LCD (4-bit interface, PCB lay-out for 16x2 character with backlight), on-board tact switch and connection for In System Programming (ISP) Port0 and Port2 as general purpose IO, are available for interfacing external devices. Port0 is connected with DIP switch, and also P0.0 and P0.1 are connected with opto-isolated input Port3, P3.0 and P3.1 are being used for serial communication UART, P3.2 for RS-485 control direction. P3.3 and P3.4 are serving as general purpose IO port pins. Another pins for communicating with serial chip, EEPROM, RTC and serial shift register (LED array indicator)..