Open Source 3 Channel Frequency Generator

[Yucca]

Hi ist,

For just PWM it would probably work out cheaper to use some dedicated chip for PWM generation. But if you want the screen for displaying freq and duty then a microcontroller like this can't be beaten.

If you get yourself an Arduino or Freeduino board from www.nuelectronics.com then I would be able to post you source code to generate PWM with it. Trouble is that nuelectronics are currently out of stock on the LCD modules, but they have just released a 4k colour 128x128 pixel screen addon for £20. The screen is a nokia unit and you could display realtime scope image of the generated PWM waves, it could be pretty cool!:

http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=10

nuelectronics are also really good, fast and cheap on international shipping, and they take paypal, I think they have great stuff at great prices!

Best, Yucca.

[z.monkey]

Howdy Yucca,

So your Arduino/Freeduino boards are prototyping boards?  What kind of processor are you using?  The DS1085 chips are serially programmable and you have an SPI port going from the processor to each DS1085.  I love those tricky little Dallas Semiconductor parts.  I live close to their plant.  So then the signals from the DS1085 go out to some power amplifiers?  What are you using for a power supply, and power amplifiers?  I noticed that you are using C++, ever get into assembly language?

I have a number of products based on Microchip Microcontrollers.  Some of these products are USB slave devices, and when in high speed mode I can get 48 MHz processor clock speeds and 96 MHz USB clock speeds.  I frequently use Hitachi LCD display products when I need to have a visual display.  Mainly I only use text displays, for cost effectiveness.  However Microchip has some new microcontroller products that have enough computational horsepower to run a QVGA GUI.  So I have been thinking about making a new visual platform which is a touchscreen GUI which is microcontroller based.  My product sales haven't been very good this year for the microcontroller based products so any new project will probably be at the hobby level and not a production level device.  I program in assembly language and compiler BASIC.  My BASIC compiler is designed around Microchip's ampasm, so I can use assembly statements in line with BASIC statements, and also write my own macros.

Had you planned on making a system overview drawing?

If you are looking for LCD deals check this place out.  http://store.earthlcd.com/

OK, Mo Later...

[Yucca]

Hi Z.Monkey,

So your Arduino/Freeduino boards are prototyping boards?  What kind of processor are you using? 

The boards come with 16MHz ATMEGA168 8 bit RISC 32K Mem.

The DS1085 chips are serially programmable and you have an SPI port going from the processor to each DS1085.  I love those tricky little Dallas Semiconductor parts.  I live close to their plant. 

Yes, I've still got to write the code to program them up. Great parts, only 8 pins but can do so much via the SPI.

So then the signals from the DS1085 go out to some power amplifiers?  What are you using for a power supply, and power amplifiers?

The unit has a small 5V supply for the MCU. I  will have my variable voltage and current benchtop supply go into the unit, this will then be chopped by the FETs in the unit. My FETs will limit my output freq. to ~25MHz but I might get faster ones in future.

I noticed that you are using C++, ever get into assembly language?

I've worked with assembly quite a bit, the good thing about C/C++ is that you can embed an assembly routine right into the code if you need fast bits just like what you're doing with ampasm. I used to work with 68000, 68HC11 and Z80 quite a bit and have done pure assembly on those, takes longer as you know but you can get nice optimised fast routines. I've noticed though that modern compilers tend to be alot cleverer with regard to optimising nowadays and I seldom need to use assembly but I still do now and then even when windows programming.

Had you planned on making a system overview drawing?

Yes, I should do that, when I've finished and settled on how I want it I will make a block diagram using a paint package.

Cheers for the link, some very fancy LCDs on that site

Best, Yucca.

[Yucca]

OK, finally got my Arduino to talk to the DS1085. That was the most difficult peripheral chip I´ve ever worked with! But it´s very sweet with less jitter than I expected, looks nice and stable on scope.

Have tested my FET drivers and they are  good for up to only 21MHz.

The unit will now only be 2 channel:
channel 1 for LF (DC ... 1MHz)
channel 2 for HF (8.2kHz...21MHz)

I´ve also put a thermometer device in that will enable the arduino to monitor the heatsink temperature and then disable output and sound a small audio alarm signal if the sink exceeds a set temp. It should help save FETs.

Now I just need to complete all the other hardware.  When finished I´ll take a few more photos of it.

[europeanhillbilly]

Now that's cool!
I ordered an Arduino Duemilanove some days ago, today I got an email it got shipped. And just NOW I find this thread - I guess my weekend is planned now!
Great job Yucca, just what we all need!
When I get my Arduino board, I'll try my best to replicate your PWM circuit. Hope you don't mind a question now and then.

Talk to you soon