Of course the other challenge of the SSB Exciter project is writing the Arduino sketch to control the three outputs of the Si5351 synthesiser. The sketch will run on an Arduino Nano with limited program memory, so can't be too fanciful and must be optimised throughout.
It needs to generate three outputs. CLK0 will be a 7.0-7.2MHz frequency for the VFO of the DCRX Direct Conversion Receiver. CLK1 will be the 11MHz input to the first SSB mixer (11054.8kHz for USB generation. CLK2 must be the mixing frequency to get the USB & LSB 11MHz signals to a final 7.0-7.2MHz for the 40m band. This is done by outputting SSB - freq for USB and a SSB + freq for LSB.
The code runs on the SIGGEN hardware designed during the BARSicle project (see many previous postings), an Arduino Nano drives an OLED display and a three output Si5351 synthesiser module, controlled by a rotary encoder with push switch.
The rotary encoder will tune in 10kHz to 10Hz steps, chosen by a short push on the encoder switch. A long 'hold' on the switch will change from USB to LSB and back. The OLED display will be simple, showing the tuned frequency (in kHz 7000.00 to 7200.00)), the sideband (USB or LSB) and the tuning step (10H to 10kHz). The previously written "Oled.h" header file using the u8g2 library will format these displays.
Here's the initial code, not yet available for download but can be cut and pasted from here, The libraries are part of previous downloads available (look below)
// SSB_EXCITER
// CLK0 = RX, CLK1 = SSB (11MHz), CLK2 = VFO (4 | 18MHz)
#include "Oled.h" // include header
#include "si5351.h" // include library
#include "Rotary.h" // include library
#define CLK 3 // encoder connnections
#define DT 2 // reverse 2&3 if wrong direction
#define SW 4
#define HOLD 500 // held button time > 0.5sec
#define CALIBRATION -150000 // frequency CALIBRATION
#define SSB 1105480000 // SSB USB freq
Si5351 dds; // create dds object
Rotary enc = Rotary(CLK, DT); // create enc object
uint64_t freq = 700000000; // first init freq (cHz), 7MHz
uint64_t freqStep = 100000; // init step (cHz), 1kHz
bool sideband = true; // start on USB
void setup() {
pinMode(CLK, INPUT_PULLUP); // encoder inputs, with pull-ups
pinMode(DT, INPUT_PULLUP);
pinMode(SW, INPUT_PULLUP);
oled.begin(); // begin OLED
dds.init(SI5351_CRYSTAL_LOAD_8PF, 0, CALIBRATION); // set xtal capacitance, 25MHz, & CALIBRATION
dds.drive_strength(SI5351_CLK0, SI5351_DRIVE_8MA); // output drive (~+10dBm)
dds.drive_strength(SI5351_CLK1, SI5351_DRIVE_8MA); // output drive (~+10dBm)
dds.drive_strength(SI5351_CLK2, SI5351_DRIVE_8MA); // output drive (~+10dBm)
dds.output_enable(SI5351_CLK0, 1); // enable
dds.output_enable(SI5351_CLK1, 1); // enable
dds.output_enable(SI5351_CLK2, 1); // enable
freqOut(freq); // output initial frequencies
dispUpdate(); // display
}
void loop() {
long hold; // button hold time
unsigned char result; // encoder result
if (digitalRead(SW) == LOW) { // enc button push
hold = millis(); // start hold count
while (!digitalRead(SW)); // wait release
if (millis() - hold > HOLD) { // button hold > HOLD time, change sideband
sideband = !sideband;
freqOut(freq); // update frequencies
dispUpdate();
}
else if (freqStep == 1000) freqStep = 1000000; // update step if 10Hz -> 10kHz
else freqStep = freqStep / 10; // step down
dispUpdate(); // display
}
result = enc.process(); // read encoder
if (result == DIR_CW) { // freq up
freq += freqStep;
freqOut(freq);
dispUpdate();
}
if (result == DIR_CCW) { // freq down
freq -= freqStep;
freqOut(freq);
dispUpdate();
}
}
// CLK0 = RX, CLK1 = SSB (11MHz), CLK2 = VFO (4 | 18MHz)
void freqOut(uint64_t freq) {
dds.set_freq(freq, SI5351_CLK0); // RX freq 7MHz
dds.set_freq(SSB, SI5351_CLK1); // SSB freq
if (sideband) {
dds.set_freq(SSB - freq, SI5351_CLK2); // VFO USB freq
}
else {
dds.set_freq(SSB + freq, SI5351_CLK2); // VFO LSB freq
}
}
void dispUpdate() { // picture loop
oled.firstPage();
do {
dispMsg(35, 0, "SSB TCVR"); // display title
dispFreq(15, 20, freq / 100, 0, 2); // display frequency, in kHz
if (sideband)
dispMsg(10, 50, "USB");
else
dispMsg(10, 50, "LSB");
dispStep(80, 50, freqStep / 100); // display step freq
} while ( oled.nextPage() );
}
