Atmel Mega88 based DDS for JUMA-line
OH2NLT 22.01.2006 / 05.08.2006
This project is dedicated for AVR nerds who can not touch anything else but AVR chips. You know people who think that AVR is the only working microcontroller architecture in the world. This is of course not true but there are some benefits using AVR like free GCC tool chain for program development.
This board is functional copy of JUMA-TX1 DDS board done with Atmel Atmega88 microcontroller. Because of higher pincountserial(RS232) interface have been added to the board for PC communication. Surface mount version (MLF package) of Atmega88 chip is used. 6-pin Atmel ISP programming connector is added for in circuit programming. This connector can also be used for general I/O in future projects. Most of the passive components are 0603 size. DDS filter components are 0805 size. PCB is industrially made double side board. Layout may be too dense for home etching. Also high count of very small vias is difficult for DIY process.
Component lay out
Double side circuit board
Atmega88 Software v1.01 Some bugs corrected, version changed to 1.01 05.08.2006
Atmel ISP tool
Software functionality is about the same with JUMA-RX1 v3.03 DDS control software. Some PC control functions have been added. Details can be found from software comments. UART input is not buffered and care must be taken not to overflow it when sending commands.
Spectrum measurements. Display: 2MHz/div, 10dB/div and BW=30kHz.
3.5MHz output | 7MHz output