https://github.com/aaronc81/bfg

Basic Function Generator - a simple function generator for embedded electronics
https://github.com/aaronc81/bfg

Last synced: 10 months ago
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Basic Function Generator - a simple function generator for embedded electronics

• Host: GitHub
• URL: https://github.com/aaronc81/bfg
• Owner: AaronC81
• Created: 2020-07-10T12:57:44.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2020-08-26T23:35:11.000Z (over 5 years ago)
• Last Synced: 2025-03-06T15:17:08.172Z (10 months ago)
• Language: C++
• Homepage:
• Size: 478 KB
• Stars: 0
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

          
# The BFG - Basic Function Generator

The BFG is a small, minimalistic function generator based around the

[AD9833](https://www.analog.com/media/en/technical-documentation/data-sheets/AD9833.pdf),

controlled by an ATmega328P with a lovely little OLED display and rotary

encoder.

![An assembled BFG, with an OLED display, rotary encoder, three generation ICs, and an ATmega328P microcontroller.](img/device.jpg)

![The BFG's display, showing frequency, wave type, power switch, and amplitude.](img/display.jpg)

![The oscilloscope output from the BFG, with the BFG and scope showing the same frequency to 3dp.](img/scope.jpg)

- Sine, square and triangle waves

- Powered over Micro USB

- Output range of 0 to 5 volts

- Theoretical maximum output frequency of 12.5MHz

At high frequencies (>2MHz) the range of voltages begins to narrow; for example,

a sine wave at 5MHz set to an amplitude of 5V only actually oscillates between

about 1.5V and 4V. These frequencies are a tad much for my poor USB oscilloscope

to handle, so I can't accurately measure the practical limits.

I built this for two main reasons:

- To have a basic function generator for embedded projects

- To learn simple surface-mount soldering

# How it Works

As the rather lovely silkscreen on the board suggests, functions are generated

by three steps:

1. **Generate**: The AD9833 generates a low-voltage signal, about 0.65V

2. **Amplify**: The AD8052 op-amp amplifies the signal to 5V

3. **Scale**: The MCP4131 digital potentiometer divides the signal down to the desired amplitude

# Repo

`cad` contains KiCad files for the PCB.

`firmware` contains a platform.io project for the ATmega328P's firmware.