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Arduino sketch for CAT controlling FT-818 with Arduino Nano and small SSD1306 128x32 display

/* FT-818 / QO-100 controller PA3ANG - May 2020 Using Arduino Nano Every with Adafruit SSD1306 128x32 OLED display. The sketch uses knobs from the FT-818 to control the functions, so no external knobs are needed. The knobs used are the CLAR, LOCK and SPLIT.

My QO-100 RF hardware consist of SG-Lab componets for uplink (transvertor and amplifier). The FT-818 and SG-Lab transverter are 
both TXCO stabile. The outdoor LNB has an TCXO build inbut does drift a bit based on the environmental temperature. 
The LNB converts down from 10489 to 432 MHz. Calibration is only needed to accomodate for the outside temperature deviations 
which are about +- 1kHz on 70cm. 

The FT-818 can be wired directly from the ACC Jack to the Ardunio digital pin 3 (RX D) and 2 (TX D) and GND. No level schifter is 

The sketch reads VFO A frequency and calculates the associated QO-100 transponder downlink frequency based on
the LNB_offset (IF) frequency and the calibartion offset (+- 1KHz). 
Based on the calculated QO_frequency the sketch calculates the uplink TX_frequency for the FT-818 to be programmed in VFO B.
The TX_frequency is calculated including the TX_LO_frequency (Transvertor IF frequency) and the QO-100 transponder 
offset 10489.500 => 2400.000 (808950000). 

The mode from the VFO A (RX) is always copied to the VFO B (TX). Note: VFO A and VFO B can be reversed if so.

Four different FT-818 statusses (or knobs) are interrogated by the sketch:

1. PTT.  If the FT-818 is transmitting nothing happens and no display updates are made.
2. CLAR. If the Clar is switched on, the calibartion procedure will start and the FT-818 VFO A RX frequency is set to the 
         Middle Beacon frequency. Pressing again the Clar knob will stop the calibration process. The new calibration offset 
         will be calculated and the RX_frequency will be set back to the frequency before starting the calibration. 
3. LOCK  If de calculated uplink TX_frequency deviates from the current TX_frequency in VFO B, the display will show the 
         an up and down arrow symbol. When pressing the LOCK knob on the FT-818 the VFO B mode and frequency will be updated.
4. SPLIT If the Split mode is switched off on the FT-818, the sketch will automatically switch it on again and program in both VFO A
         and B the Home frequency with Mode USB. 

The calibration process works as follows:
RX is set to LSB and the Middle Beacon frequency. Adjust to zero beat (you will hear a low tone +- 200Hz) and when switching
to USB the tone should be the same +- 200Hz. You need to experiment a bit but when know know how it works this calibration can
be done very fast. The program will switch 
back to USB after pressing Clar again.



Arduino sketch for CAT controlling FT-818 with Arduino Nano and small SSD1306 128x32 display






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