TEST DDS Si5351 VFO JAN CIGER DENGAN BITX BIXEN : janoc.rd-h.com... #dds #yg3fzi
Beli modul si5351 shope.ee/50Cts...
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Here is an older project of mine - another variant of a VFO. This time with the popular Si5351 clock generator, allowing to create a complete solution for a superhet, including both the VFO and BFO oscillators.
Features
The VFO has the following features:
Independent VFO and BFO oscillators
RIT/XIT offsets
Tx signal input - used to let the microcontroller know when to apply the XIT offset
Same display layout as the AD9850 VFO
Revised controls - gone are the complicated button combinations, there is now a menu for configuring things such as the IF and BFO frequencies, operating mode, IF mode, etc.
Output limited to 1MHz-30MHz (but easily changeable in the code)
Supports both 3.3V and 5V LCD modules
Easy to adapt to different IF filter frequencies and setups
Arduino compatible
2019/11/9 - EEPROM persistence for the settings and frequencies
Schematic
The VFO uses a standard ATMega328P-AU (in TQFP-32 package), running from the internal RC oscillator at 8MHz. The frequency generation is provided by Si5351a, running from a 25MHz crystal, with all 3 outputs routed to the edge of the board (should fit an SMA connector). In my case the loading capacitors C6, C7 weren’t necessary because my crystal needs only few pF of capacitance - the parasitic capacitance of the PCB is sufficient there.
The user interface is provided by 4 tactile switches (SW1, SW2 & SW3 + RESET) and a clickable rotary encoder (SW4). The output uses a standard 1602 LCD module1. Both 3.3V and 5V (most common) LCDs are supported - select the desired voltage by shorting the corresponding pads of the J4 jumper.
Basic controls
Encoder left/right Tuning, menu navigation, changing values
Encoder button Change tuning step, confirm selection
Button A Hold down to enter “cursor” mode where you can rapidly dial in the desired frequency decade by decade
Button B Set RIT offset (XIT when /RIG_TX is active as well)
Button C Enter/exit the settings menu
The numeric settings (such as the IF and BFO frequencies in the settings) are changed by clicking the encoder, scrolling the cursor to the decade you want to adjust, clicking again to confirm and then rotating the encoder to change the value. Click to confirm again. The mode is exited by moving the cursor completely to the left of the display and clicking the encoder button again.
Settings
Operating mode - for the offsets see below
AM BFO off
LSB BFO freq = BFO center + BFO SSB offset
USB BFO freq = BFO center - BFO SSB offset
CW BFO freq = BFO center - BFO CW offset
IF mode
Off Frequency on display is the frequency output
F+IF VFO outputs the displayed frequency + the configured IF (additive IF)
F-IF VFO outputs the displayed frequency - the configured IF (subtractive IF)
IF & BFO frequency
IF and BFO center frequency, useful for peaking filters, etc. The default in the code is 8987.5kHz because that is the center frequency of a surplus Yaesu filter my receiver is using.
Invert sidebands
A small hack that reverses the meaning the LSB/USB modes when active. Rarely useful, mostly for debugging and testing.
Configuration
Everything that is configurable is collected in the file definitions.h. The following values are likely the ones that will need to be customized depending on your radio (filters, etc.):
Variable Initial value Meaning
VFOFreq 7100000 Initial frequency of the VFO in Hz
IFFreq 8987500 Initial IF frequency in Hz
BFOFreq 8987500 Initial BFO frequency in Hz. BFO center frequency in Hz. Frequency from which the offsets are subtracted/added.
BFOSSBOffset 1250 How far to offset the BFO from the center when receiving SSB. Normally it should be 1/2 of the bandwidth of your IF filter.
BFOCWOffset 600 How far to offset the BFO from the center when receiving CW.
TuningIncrements 100000, 10, 50, 100, 500, 1000, 2500, 5000, 10000 Available tuning steps in Hz
RitIncrements 10, 100, 1000, 1 Available RIT/XIT tuning steps in Hz
TuningIncrementIdx 4 Initial tuning step (500 Hz in this case)
RitIncrementIdx 0 Initial RIT tuning step (10 Hz in this case)
Rit 0 Initial RIT in Hz
SidebandsSwap false Initial value of whether to swap the meaning of LSB/USB mode setting
FreqLimitUp 30e6 Upper frequency limit for the VFO (30 MHz)
FreqLimitDown 1e6 Lower frequency limit for the VFO (1 MHz)
SI5351Addr 0x62 I2C address of the Si5351a - according to the datasheet it should be 0x60 but chips with 0x62, 0x6f are common too. Try to change if the VFO is not tuning.
SI5351Correction 2004 Frequency correction for the Si5351 crystal - if you have accurate counter you could try to tweak this to calibrate the frequency of the VFO
18 сен 2024
