LCD menu control
All actions can be viewed in LCD menu. Menu can be controlled with 5 buttons that are next to LCD module.
Up and down arrow buttons are used for browsing menu while right and left arrow buttons are used for changing frequency value. When middle button is pressed - signal generating starts. Press middle button again to stop signal generator.
Important to notice, that there is a separate menu for changing frequency step. This is convenient if you need to change generator frequencies in wide range. This allows to set any frequency with relatively few button clicks.
Noise generation don’t have frequency setting. It uses simple rand function where results are continuously output to DDS output.
High speed signal has four frequencies available: 1, 2, 4 and 8MHz.
Circuit diagram of DDS generator is very simple with easy accessible components. It uses following parts:
• AVR Atmega16 microcontroller clocked with 16MHz external crystal;
• Standard HD44780-based 2x16 LCD module;
• R2R DAC made of simple resistors(1% tol);
• LM358N low power dual op amplifier;
• Two potentiometers;
• 5 buttons;
• several connectors and sockets.