In fact Budd’s software sketch will work just fine with my circuit although it will operate a little differently to mine.įor my project I’ve integrated WB7FHC’s audio filtering circuit with a standard Arduino Nano and modified his software for my own feature preferences. You are of course welcome to try and use Budd’s sketch in this project, you may prefer the operation of his decoder software to mine.Īs with several of my projects, I am using the Arduino Nano for this project due to its conveniently small size. If you prefer or have one on hand, you can use an Arduino Uno if you wish, its just bigger and will require a larger case.Īs indicated earlier, I have integrated WB7FHC’s audio filtering circuit with an Arduino Nano. The circuit consists of an LM567 tone decoder, an MPC41010 digital potentiometer, an Arduino Nano and an LCD. The LM567 is a tone decoder with its centre frequency controlled by a voltage controlled oscillator (VCO). The VCO frequency is set by capacitor (C4) and a variable resistor placed across pins 5 & 6. Capacitors C1 & C2 form a filter with the bandwidth set by the value of C1. Using the component values provided, the bandwidth and frequency range is selective enough that you can select one of several stations that are transmitting close together just by tuning that station to the correct tone. Audio tones from the receiver are fed into pin 3. The output pin 8 normally floats to a logic high due to its output load R1/D1, however if the audio tone at the input matches the frequency of the VCO, the output pin 8 switches low. Hence the LM567 is able to turn a correctly tuned Morse code tone at the input into a series of logic 0s and 1s at the output. D1 switches on whenever pin 8 switches low giving a visual representation of the incoming Morse code. It provides a variable resistance across pins 5, 6 and 7 simulating a normal 3 terminal variable resistor or potentiometer. The value of the resistance is controlled by serial input data from the Arduino applied to pin 3. Pin 2 receives serial clock timing pulses from the Arduino to control the timing of the incoming data. Pin 1 is the Chip Select pin used to enable the MPC41010 for data control. Since the outputs on pins 5, 6 & 7 perfectly simulate a variable resistor, they can be connected directly to the pins 5 & 6 on the LM567 to precisely tune the LM567’s VCO frequency using serial data from the Arduino. The LCD is a 4 line x 20 character backlit display. *This information is for general informational purposes only, we will not be liable for any loss or damage caused by the above information.It can be purchased locally for under $10 shipped or even less from China. The company was acquired by Texas Instruments in 2011 and its products and technologies continue to be developed and sold under the Texas Instruments brand. National Semiconductor's products were used in a variety of applications including consumer electronics, industrial, automotive, and telecommunications. The company was known for its innovations in the field of analog and mixed-signal integrated circuits and was a leading supplier of power management and data conversion products. National Semiconductor was an American semiconductor company that was founded in 1959.
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