admin
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AVR DDS signal generator V2.0 (http://www.scienceprog.com/avr-dds-signal-generator-v20/) have got lots of attention. Some people claim that analog part is rubbish – signal seems to be distorted at higher frequencies. Some would like to see more features. So I came to thought of starting third version of DDS generator. But before start some feedback from you would be great. Considering comments and suggestions here are some thoughts:
Platform
Should I stick with AVR? Have several spare Atmega328P why not run at 20MHz. SMD or DIP?
ARM – older LPC2106 or Cortex-M3? These would allow squeeze higher frequencies with software DDS algorithm, but idea of simplicity would be lost – ARM is more complex.
Features:
Dedicated high speed (HS) output (already in DDS V2.0);
Variable amplitude and offset (already in DDS V2.0);Use better OP-Amp (maybe OPA2134)
DDS signals: sine, square, saw, rev saw, triangle, ECG and noise (already in DDS V2.0);
LCD (already in DDS V2.0); Maybe graphical?
5 button keypad (already in DDS V2.0); Other ideas (rotary encoder?, navigation button);
Sweep function (planned on DDS V3.0);
PWM (planned on DDS V3.0);
Frequency change while signal is generating (probably on DDS V3.0);
Arbitrary waveform generation (probably on DDS V3.0);
DDS part:
Use R-2R ladder;
Use specialized DAC chip;
Use specialized DDS chip (faster, easier to add new features).
Please share your suggestions. What OP-AMP would result in clearer waveform and still would be widely accessible. Widely accessible DAC and DDS chips?
P.S.
How many of you built DDS V2.0 and would like to see software updated for it?
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Tihomir Benko
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Hi,
I built DDS2 and I wont to see some software updates, like sweep function (only on sine vawe will be enough).
DDS3 is a good idea. I use LF353 (pin2pin compatible with LM358) and I can save and send screenshots from DSO osciloscope.
Tihomir.
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admin
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Considering to use TL074 quad amp for analog part. Its a low noise cheap amplifier. Any thoughts?
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admin
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Just finished to model analog part of AVR DDS3
http://www.scienceprog.com/modeling-of-analog-part-for-dds3-signal-generator/
Comments on critical parts would be welcome.
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hrs1990
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Make a custom signal generation system like the DAC values will be written in an EEPROM or memory card from a program in PC and the signal generator will generate the signal that u designed in ur pc
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admin
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I am planning on using two AVR chips. One will be smaller (probably Atmega88PA) for generating DDS signal. Another with more Flash memory (Atmega328P) for user interface and storing waveform tables. Split MCU design will allow more flexibility on user control without interrupting waveform. I think to load wave form bigger MCU to smaller one SRAM memory using SPI (I2C?) interface and send commands to it using external interrupt source. Working on initial schematic drawing currently. Any great ideas are welcome
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Bingo
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need the frequency step smaller than 1HZ
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