It is a receiver based on CI Si4735 controlled by Arduino with SSB support (amateur radio) conetroled by Arduino. This receiver uses the "Si4735 Arduino Library" written by PU2CLR (Ricardo Lima Caratti) and also can be used by others host MCU like (ESP32 and STM32).
1. Encoder to tune stations;
2. Band selection via push buttons
3. AM, FM and SSB;
4. LW, MW and SW;
5. Bandwidth filter;
6. BFO Control;
7. VFO/BFO switching via encoder push button;
8. 12 SW bands + one from (100KHz to 30MHz).
9. Frequency step switch (1, 5, 10, 100 and 500KHz KHz);
* Try to follow what the Silicon Labs recommends; * Start building the minimum circuit and test it; * Check if the Si47XX RESET pin (15 on SSOP version or 5 on QFN version) is connected on your MCU (Arduino) pin defined as RESET the (the most of schematics and examples of this project this pin is the digital pin 12); * Use the minimum sketch to test the minimum circuit. The first three examples of this project (see examples folder) can be used to test the minimum circuit; * Try not improvising the I²C bus connection. Start using a 3.3V MCU (Arduino Pro Mini 8MHz or DUE, ESP32 or other 3.3V device) to connect with SI4735; * Some devices provide internal pull-up resistors that in some cases can be enabled or disabled. Also, the capacitance of the I²C bus is another variable that have be considered to select the right resistor values. However, that capacitance is not easy to be measured. For these reasons, it can be a liitle dificult calculate the right resitor values at first. That said, start with a high pullup resistor to I²C bus and then reduce it until the best value. For example: start with 10K and try to reduce the value to 4,7K, 3,3K, 2.2L etc. Select the lowest resistor you can. * I²C bus devices are available in different speeds. If you are using an I²C display device, check if its speed is compatible with the Si47XX and also with the current speed used by the master MCU; * Using different voltage levels between I²C devices can be unsafe and can destroy parts connected on I²C bus, specially the Si47XX; * It is important to wire all your I²C devices on the same common ground. * If you are using Arduino Mini Pro, ONU or similar, pay attention to the pin 13 and the use of internal pull-up resistor. This pin has a LED and a resistor connected on the board. When this pin is set to HIGH the LED comes on. If you use the internal pull-up resistor of the pin 13, you might experiment problem due to the drop voltage caused by the LED circuit. If this occurs in your project, change the circuit to use external pull-up on pin 13. * Use only batteries to power your circuit. Receptions in LW, MW and SW can be seriously harmed by the use of power supplies connected to the grid. * See some Shortwave antenna configuration on [Si47XX ANTENNA, SCHEMATIC, LAYOUT, AND DESIGN GUIDELINES; AN383](https://www.silabs.com/documents/public/application-notes/AN383.pdf)