gerryk.com

34,The DDS and related clock generation circuitry has made possible high accuracy, broad-banded programmable VFO functionality for very little money.;Analogue Devices’ AD9850;series offer HF frequencies for about;€5. Higher frequencies can be had for not much more money, with the Silicon Labs SI570 with its near GHz maximum frequency offering the highest. I recently came across;an interesting little device from Adafruit. Again, from Silicon Labs, the SI5351;offers 3 independent clock outputs from a single 25MHz reference, programmable via i2c, a maximum frequency of 160MHz and all for less than;€10 shipped. I had to have one. \nThe order, along with some of the other wonderful goodies from Adafruit arrived soon enough, and I got to work, first off getting the encoder knob working. The plan was to have a rotary encoder with push button for setting the freqeuncy, an i2c LCD for display, and the clockgen, all hanging off an Arduino… in this case, a Leonardo clone. \n \n \n \nThe sample code I first tried for the encoder worked ok, but then I found the builtin ‘encoder’ library, and tried that… far better, and no messing with interrupts. \n \nNext, I tried to get the display working… no joy using the standard LiquidCrystal_I2C library. I then ran an i2c scanner to find out if the device perhaps had a different address from standard. This gave me a ‘no devices’ error… something was wrong. After a bit more research, I discovered that the pins used for i2c on the Leo’ are not the same as on the Uno.;The Uno uses Analog pins 5 and 6 , whereas the Leo’ uses Digital pins 2 and 3. I reran the scanner, and it immediately detected the display on 0x27 ;and the clock-gen on 0x60. I plugged the address into some display testing code and had my display! \n \n \nI then added in a few lines to include the Adafruit si5351 library and program one of the clocks to output 14Hz. I had my AOR8200 MkIII to hand, tuned to 14MHz AM so I hoped to be able to hear the clock on the AOR receiver. Nothing, however. A bit more reading, and I came across;another library for the SI5351… this one managing to avoid all the divider/multiplier calculations necessary with the Adafruit library. I modified the code once again to include this, and instead of doing any calculations, just wrote the required frequency directly to the clock. This time, I could hear a tone on the receiver. As I turned the encoder, the frequency on the display changed, and I could hear the tone get slightly higher in pitch… success by any measure. \n \nIt only remains to case this and use it to align a few projects. \n \n; \n \n