This is an IC that can digitally synthesize frequencies up to 25MHz using DDS. It requires very few external components, but it is only available in SSOP-16. I successfully prototyped with this using a SSOP to DIP adapter and solderless breadboard (probably not the best idea given the 50MHz clock, but it worked).
A breakout board for this IC should be fairly cheap to produce. The IC is around $10 qty 1 from DigiKey, and just a few resistors/capacitors and an xtal oscillator are needed for a fully functioning DDS synthesizer. If the selling price could be kept under say $50, I’m sure many hobbyists (especially hams) would be interested.
Have you seen the DDS-60 kit offered by AmQRP? They offer a 0-60Mhz DDS kit using the AD9850 chip including the low pass filter for $28 (you supply the AD9850). They even have someone lined up to solder the 3 SMD chips for you, if you require it.
Thanks riden, I was not aware of the kit service. I did run across the 2nd site you had listed - in fact, used it to help me with coding the software. I ended up using a Basic Stamp 2 for my software - made for quick testing but it did take me a while to find some 32-bit math routines I could use to compute register values for the desired frequency.
You’re welcome. It is truly amazing what these little things can do. Sure beats the daylights out of an synthesizer I built out of TTL components many years ago! I will be replacing a defective VFO in my HF rig with a AD9850 based DDS when I get a little quality time to tinker. So many projects, but so little time!
Will this thing work down in the audio frequencies? I need a signal generator in the 10 Hz - 15 kHz range. Briefly looking at the spec sheet I don’t see any reason it shouldn’t even with a 50 MHz clock. If my math is right, it looks like you’d have 0.01 Hz steps.
You might look at miniDDS which uses an AVR chip and goes from “DC” to around 300KHz with sine, square, sawtooth, and triangle waveforms. I added a digital potentiometer and it works very well (not perfect, but great for my audio purposes).
I built my first one using a PIC but the upper frequency range was limited to around 60KHz because I couldn’t get my loop running as fast as on the AVR.
JonChandler:
Will this thing work down in the audio frequencies? I need a signal generator in the 10 Hz - 15 kHz range. Briefly looking at the spec sheet I don’t see any reason it shouldn’t even with a 50 MHz clock. If my math is right, it looks like you’d have 0.01 Hz steps.
You are correct. The clock frequency can be multiplied by any value you select between 1/2^32 and 2^32/2^32. With a 50MHz clock this works out to around 0.01Hz. And also you need not use a 50MHz clock - a lower frequency will also work if for some reason 0.01Hz resolution is not enough.
A very old thread I know (5yrs since anyone last posted!!!), but I’ve just ordered two of these & have resurrected it rather than starting a new thread!
It’s my first dabble with a DDS chip & to be honest I’m finding find the datasheet a bit over whelming (I know how to drive SPI etc, but like erhm eh?) …it’s touted everywhere as being able to do up to 10Mhz in 1Hz steps, but like a previous poster on this thread, I want to use it in the audio range - it’s not clear to me how you get (or if you can get) the thing to resolve to two decimal places (eg between 0Hz & 20,000Hz …ie at like to be able to generate frequencies like 1000.15Hz etc…do-able?
I’d like to have used this IC on a pcb and sharing the oscillator with a PIC (upto 20Mhz) - so will I be able to get the two decimal point granularity in the audio frequency range (what’s the lowest I could have for an oscillator)