Assemble the device and upload the firmware. Connect active GPS antenna, antenna for WSPR message transmission and USB-B cable for device power supply.
Note
It is recommended to use full-size antennas for a specific transmission range, as their efficiency is significantly superior to that of wideband and compact antennas. Also, it is recommended to use bandpass filters that suppress unwanted signals outside the operating range (the SI5351 emits unwanted harmonics along with the main signal emission at the operating frequency).
The device operates in fully automatic mode. Turn on the device by switching the SW1 toggle switch position. After switching on the device the green LED (ON) should light up, which means that the device is working correctly and the initialization process has started.
Note
During the device operation you will have access to logging of all actions performed by the device through the use of "Tools" -> "Serial Monitor" in Arduino IDE.
Initialization of the hardware is performed in the void setup() function and is executed only once, when the device is started.
By default, the SI5351 is initialized at I2C address 0x60, if no device can be detected at this address - a reboot is performed. If you encounter any problems at this stage - make sure that your SI5351 instance really has I2C address 0x60! If necessary, you can change the value of the I2C address of the SI5351 in the firmware source code.
The GPS module used in the device operates using a software-implemented serial port. Initialization of the GPS module starts with checking if any information is available from the GPS receiver on the virtual serial port. If no data is received within "GPS_INIT_MAX_TIME" - the device will be rebooted. If the connection is successfully initialized, time synchronization and calculation of your QTH locator (WSPR protocol requirement) is performed based on the data received from the GPS module. The device performs "GPS_SYNC_ATTEMPTS" attempts to synchronize GPS data with a delay of "GPS_SYNC_DELAY". If all synchronization attempts fail, the device is rebooted.
Warning
The device will not transmit WSPR messages until the time and coordinates are synchronized!
Successful completion of GPS data synchronization is signaled by the green LED (GPS), after which the device enters the main cycle of WSPR message transmission.
Transmission of WSPR messages is performed in an infinite loop void loop() every even minute (00:00, 00:02, 00:04, ...). Each transmission cycle is executed at a randomly selected frequency within the range of +/- 100 Hz from the center operating frequency. During the WSPR message transmission, the red LED (TX) lights up and goes out immediately after the transmission is completed. After completion of the transmission cycle, the device re-synchronizes the time and coordinates based on the current GPS data values.