Fmilburn 446 Posted March 1, 2016 Share Posted March 1, 2016 This project uses an inexpensive AD9850 board obtained off eBay to create a frequency generator boosterpack that is especially useful with the MSP-EXP430FR6989 LaunchPad. It features an encoder with a pushbutton to adjust frequency. In the photo below it is generating a 7000 Hz signal which agrees nicely with the oscilloscope. The schematic is simple: The encoder is a Bourns 652-PEC12R-4225F-S24. I tried various arrangements and value of resistors and capacitors for debouncing the encoder and switch. In the end I just added some capacitance as shown in the schematic. On the oscilloscope it looked pretty clean so I called it good enough. All the parts are through hole as seen in the photograph below: The fit is tight but fortunately all the materials were on hand when the PCB was being designed so I printed out a paper PCB outline and checked it before ordering. If I were making it again I would increase the size of the board a bit to allow larger/additional labels. Otherwise, everything works and it turned out fine. This is a picture of the unpopulated boards I received from Osh Park. While it should work with most LaunchPads I had the FR6989 in mind as I developed it - in particular I wanted to use the integrated LCD display. Accordingly, I was careful not to obscure the display or the reset button. The software was developed with Energia V17. Here is a photo of what it looks like in operation: The output from the AD9850 comes out the jumpers attached to the 90 degree male header pins marked with arrow A. The dark jumper wire is GND and the sine wave is coming out of the lighter wire on the right. Adjustments are made with the encoder knob marked by arrow B. Turning it adjusts the frequency up and down and the current value is output on the LCD as shown by the arrow C. The range is from zero to 32 MHz. Since fine adjustment is desired, as well as rapid adjustment, the push button on the encoder is used to change the coarseness of the adjustment. The magnitude is indicated by the battery indicator on the LCD as shown by arrow D. For example, in the photo three battery bars are showing which indicates that each adjustment/click of the encoder will change the output by 1000 Hz. When the encoder is pushed down it will cycle through in this case to 100 Hz adjustment (with two bars showing), 10 Hz (one bar), 1 Hz (no bars), and then up to 1 MHz (six bars), and so on. In practice, it adjusts pretty quickly with good resolution. One enhancement might be to have the software scroll the output value since as is it won't display full resolution due to the 6 digit screen. The Energia sketch can be found here. I have an extra PCB so if you are active in the 43oh forums and would like it then send me a personal message and I will mail it gratis. yosh, dubnet, chicken and 4 others 7 Quote Link to post Share on other sites
yosh 121 Posted March 1, 2016 Share Posted March 1, 2016 @@Fmilburn very nice project and well written summary. Do you share your pcb design at oshpark ? Searched for it but couldn't find it ... Quote Link to post Share on other sites
Fmilburn 446 Posted March 1, 2016 Author Share Posted March 1, 2016 Hi @@yosh - I went ahead and shared it on OSH Park under the title AD9850. There is one unusual thing about the rendering of the top layer of the PCB on the OSH Park site. The footprint of the AD9850 as I drew it in KiCad extends beyond the actual PCB and OSH Park's display software picks up the whole thing even though the size (and cost) of the PCB is smaller. The actual size is as shown in my photographs above. The bottom layer as shown at OSH Park is correct. One other thing I thought I would mention. When designing the board I thought the tabs on the encoder that can be used to snap it in place might cause an interference problem so I didn't make slots for them in the board. Accordingly, you must pinch them off before soldering the encoder. yosh 1 Quote Link to post Share on other sites
terjeio 134 Posted March 1, 2016 Share Posted March 1, 2016 @@Fmilburn, nice project. Something to consider for my MSP430FR4133 LaunchPad currently collecting dust in a drawer. I am using a soundcheck CD as a signal generator for now, a real one would be nice. Quote Link to post Share on other sites
yosh 121 Posted March 2, 2016 Share Posted March 2, 2016 Hi @@yosh - I went ahead and shared it on OSH Park under the title AD9850. Thanks @@Fmilburn ... ordered Quote Link to post Share on other sites
Fmilburn 446 Posted March 2, 2016 Author Share Posted March 2, 2016 @@yosh, @@terjeio, If you or others who contribute regularly to 43oh want one of my extras (I have 2) just let me know and I am happy to mail no charge. Otherwise they will sit in my desk and never get used. veryalive and yosh 2 Quote Link to post Share on other sites
dubnet 238 Posted March 2, 2016 Share Posted March 2, 2016 @@Fmilburn Great project! Appreciate your offer of the PCB and would like to request one. Also if you had good luck with the vendor you sourced the AD board, would you mind passing that info along? Please PM me and I can give you my address. Thanks! Quote Link to post Share on other sites
Fmilburn 446 Posted March 2, 2016 Author Share Posted March 2, 2016 @@dubnet - Will PM you. The vendor was ZJchao, titled "ZJchao Active AD9850 DDS Signal Generator Module 0-40MHz Test Equipment" and looking back it seems I got it off of Amazon but they are also on Ebay. Quote Link to post Share on other sites
veryalive 49 Posted March 2, 2016 Share Posted March 2, 2016 @@Fmilburn It is very kind of you to offer your board to the community. Bravo. If there is a spare one, may I request it? I have both an AD9850 and a 6989 LP in my lab. If you are OK with this, I can give you some more details via PM.... Cheers. Quote Link to post Share on other sites
Fmilburn 446 Posted March 2, 2016 Author Share Posted March 2, 2016 @@veryalive Sure, send me a PM. I never expected this much interest to be honest. That will be the last of the ones that I had made. Let me know how it works for you. Quote Link to post Share on other sites
veryalive 49 Posted March 3, 2016 Share Posted March 3, 2016 Many thanks. I'll PM you my details. At the moment, I have some connectivity issues with the forum PM service; so I'm replying to you via this forum. Cheers, Quote Link to post Share on other sites
yosh 121 Posted March 15, 2016 Share Posted March 15, 2016 Got my AD9850 BP PCBs from Oshpark these days ... thanks again for sharing your project there @@Fmilburn So I have two PCBs I could give away to active members (let's say 20 posts+ ? ... hope this is ok !?) ... I would send them for free inside Europe, no problem. bluehash, reaper7 and Fmilburn 3 Quote Link to post Share on other sites
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