Si4844 Library for Arduino

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This Arduino library was developed to work with the SI4822, SI4826, SI4827, SI4840, 4844A, and 4844B “BROADCAST ANALOG TUNING DIGITAL DISPLAY AM/FM/SW RADIO RECEIVER” devices. It is available on Arduino IDE. This library is intended to provide an easier interface to control the SI48XX family.

The SI4844, along with other devices in its family, provides the ideal combination of analog tuning and digital interface, enabling the development of receivers reminiscent of the iconic models from the 1970s and 1980s. These classic receivers featured visual interfaces using liquid crystal displays or LEDs, offering a unique and nostalgic user experience. Therefore, a notable application for the SI4844 is the construction of a vintage-style receiver that blends retro aesthetics with modern technology.

Use the ‘Content Index’ of this documentation and the example sketches, especially SI4844_00_POC.ino, to make the most of this library.

This library can be freely distributed using the MIT Free Software model. Copyright (c) 2019 Ricardo Lima Caratti

Contact: pu2clr@gmail.com

By Ricardo Lima Caratti, Oct 2019.

Donate

If you find this project useful, consider making a donation so that the author of this library can purchase components and modules for improvements and testing of this library. Click here to donate.

About Me

I hold a Master’s degree in Educational Technology from the Federal University of Ceará, where I delved into the ways technology can enhance learning experiences. My passion for computer science led me to specialize in it, focusing on Distributed Systems Development with an Object-Oriented approach, at the University of Brasília. My academic journey began with a Bachelor’s degree in Information Systems from the União Pioneira de Integração Social (UPIS-Brasília). Outside the classroom, my main hobbies are electronics and Amateur Radio.

Contents

1. License Copyright
2. Your support is important
3. About the SI4844 Architecture
4. Terminology
5. Labrary Features
6. Library Installation
7. Hardware Requirements and Setup
   • Schematic
   • Component Parts
   • Photos
8. API Documentation
9. References
10. Source code - Arduino Examples
11. Videos

PU2CLR SI4844 Arduino Library

Example using LCD16x02

See also

• PU2CLR Si4735 Library for Arduino. This library was built based on “Si47XX PROGRAMMING GUIDE; AN332” and it has support to FM, AM and SSB modes (LW, MW and SW). It also can be used on all members of the SI47XX family respecting, of course, the features available for each IC version;
• PU2CLR SI4844 Arduino Library. This is an Arduino library for the SI4844, BROADCAST ANALOG TUNING DIGITAL * DISPLAY AM/FM/SW RADIO RECEIVER, IC from Silicon Labs. It is available on Arduino IDE. This library is intended to provide an easier interface for controlling the SI4844.
• PU2CLR AKC695X Arduino Library. The AKC695X is a family of IC DSP receiver from AKC technology. The AKC6955 and AKC6959sx support AM and FM modes. On AM mode the AKC6955 and AKC6959sx work on LW, MW and SW. On FM mode they work from 64MHz to 222MHz.
• PU2CLR KT0915 Arduino Library. The KT0915 is a full band AM (LW, MW and SW) and FM DSP receiver that can provide you a easy way to build a high quality radio with low cost.
• PU2CLR BK108X. The BK1086 and BK1088 are DSP receivers from BAKEN. The BK1088 is a BROADCAST FM and AM (LW, MW and ) RECEIVER and BK1086 is a subset of the BK1088 (it does not have LW and SW acording to the Datasheet).
• PU2CLR RDA5807 Arduino Library. The RDA5807 is a FM DSP integrated circuit receiver (50 to 115MHz) with low noise amplifier support. This device requires very few external components if compared with other similar devices. It also supports RDS/RBDS functionalities, direct auto gain control (AGC) and real time adaptive noise cancellation function.
• PU2CLR SI470X Arduino Library. It is a Silicon Labs device family that integrates the complete functionalities for FM receivers, including RDS (Si4703).
• PU2CLR MCP23008. It is an Arduino Library to control the MCP23008/MCP23S08 8-Bit I/O Expander. The MCP23008 device provides 8-bit, general purpose, parallel I/O expansion. It can be controlled via I2C bus applications. It is a great and inexpensive device that allow you to add more devices to be controlled by your Arduino board via I2C protocol.
• PU2CLR - PCF8574 Arduino Library. It is an Arduino Library to control the PCF8574 8-Bit I/O Expander. The PCF8574 device provides 8-bit, general purpose, parallel I/O expansion. It can be controlled via I²C bus applications. It is a great and inexpensive device that allow you to add more peripherals to be controlled by your Arduino board via I²C protocol.
• QN8066 FM DSP RX/TX Arduino Library. An easy-to-use interface for controlling the QN8066 FM transceiver and receiver.

More Arduino Projects developed by author

• Multipurpose signal generator with SI5351. It is a multipurpose signal generator controlled by Arduino. This project uses the SI5351 from Silicon Labs. The Arduino sketch is configured to control the SI5351 with three channels from 32.768KHz to 160MHz and steps from 1Hz to 1MHz.
• Shortwave Arduino Transmitter. This project is about a shortwave transmitter from 3 MHz to 30 MHz. It uses the SI5351 oscillator from Silicon Labs controlled by Arduino. Also, you can use it with a crystal oscillator. In this case, you will not need the SI5351 device and Arduino.
• Android and iOS Bluetooth Remote Control for PU2CLR Arduino Library DSP receivers. This project is an extension of the Arduino library projects for: SI4735; AKC6959 and KT0915. It is a simple example that shows a way to use your smartphone as a remote control via Bluetooth. In order to follow the steps presented here, I am assuming that you have some knowledge in development for mobile devices. Also, you will need to be familiar with the Javascript programming language. The development environment used by this project is the Apache Cordova. Cordova is a open-source mobile development framework that allows you to develop cross-platform applications. That means you can code once and deploy the application in many system, including iOS and Android. Cordova provides an easy way to develop for iOS and Android.
• Band Pass Filter controlled by Arduino. It is a HF band pass filter controlled by Arduino. It is designed for HF receivers. With this project, you can use a set of up to four HF bandpass filters that can be selected by Arduino. To do that you will need just two digital Arduino pins.

Important

The SI4844 is a 3.3V part. If you are not using a 3.3V version of Arduino, you have to use a kind of 5V to 3.3V converter. See Hardware Requirements and Setup.

A good alternative to the Arduino Uno or Arduino Nano for a project using the SI48XX device is a board based on the LGT8F328 microcontroller. This device offers excellent compatibility with the Arduino Nano and Uno, including pin configuration, with the added advantage of operating at 3.3V, eliminating the need for a bidirectional converter, and being more affordable. Other viable alternatives include the ESP32, ESP8266, and STM32.

MIT License

Copyright (c) 2019 Ricardo Lima Caratti

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE ARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Your support is important.

If you would like to support this library development, consider joining this project via Github. Alternatively, make suggestions on features you would like available in this library. Thank you!

About the SI4844 Architecture

The Si4844 is an analog-tuned digital-display AM/FM/SW radio receiver. It has an analog-tune while frequency, band, and setero/mono information can be displayed on LCD. It works with a I2C protocol that allows a microcontroller send command and receive data. Also, with a 100K variable resistor, you can simulate a dial mechanical tuning wheel found in old or traditional receiver. In this way, you will be able to offer a look similar to the old radios.

See more about SI4844 on BROADCAST ANALOG TUNING DIGITAL DISPLAY AM/FM/SW RADIO RECEIVER

Terminology

Term	Description
Arduino Libraries	Libraries are files written in C or C++ (.c, .cpp) which provide your sketches with extra functionality. The SI4844 Library provides extra functionalities to make easier the Arduino deal with Si4844 device
CTS	Clear to send
IDE	Integrated Development Environment
I²C	I²C - Inter-Integrated Circuit
Sketch	Name that Arduino environment uses for a program
ATDD	Analog Tune Digital Display. Sometimes used to refer the Si4844 device
interrupt	In this context, it is a Arduino Resource. Allows important tasks to be performed regardless of the flow of your program
C++	A object-oriented programming (OOP) language. It is a superset of the C language with an additional concept of “classes.”
programming guide	In this context it refers to Si48XX ATDD PROGRAMMING GUIDE
POC	Proof of Concept
SDIO / SDA	Serial data in/data out pin
SCLK / SCL	Serial clock pin

Library Features

1. Open Source. It is free. You can use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software. See MIT License to know more.
2. Built Based on Si48XX ATDD PROGRAMMING GUIDE
3. More than 30 Si48XX functions (methods)
4. Extended SW band frequency ranges: 2.3–5.6 MHz and 22–28.5 MHz
5. C++ Lenguage and Object-oriented programming
6. Available on Arduino IDE (Manage Libraries)
7. Simplifies SI4844 based projects

Library Installation

You can install the library via the Arduino Library Manager. Go to the menu Sketch > Include Library > Manage Libraries…, and in the search box, type “PU2CLR SI4844”.

The images below show that actions

You can also download this library or old version of it via this repository or via Arduino Library List.

Hardware Requirements and Setup

This library has been written for the Arduino platform and has been successfully tested on Pro Mini 3.3V (8MHz). I beleave it will work on any other Arduino with I2C support.

Arduino 5V and Si4844

The Si4844 is a 3.3V part. If you are not using a 3.3V version of Arduino, you have to use a kind of 5V to 3.3V bidirectional converter. It is important to say that just power the Si4844 device with 3.3V from Arduino board is not enough. You have to be aware that the Arduino that operates with 5V, the digital pins and the I2C bus will send 5V signals to the Si4844 device. That configuration can make the system unstable or damage the device.

I have tested it with success the SI4844 with a 5V Arduino using the I2C Multiplexer TCA9548A, that also can work as a bidirectional converter.

See that approach here.

Schematic

Schematic with Arduino Pro Mini 3.3V and OLED

To use this labrary you need to build a radio based on SI4844 connected to Arduino. The schematic and photos below show the hardware and setup requirments for start using this library.

Arduino and OLED circuit

SI4844 minimal circuit

As you can see above, that is a very simple circuit with minumum component parts. The push button are used with the internal Arduino pull up resistors. The OLED display and the SI4844 are connected on the A4 (SDA) and A5 (SCL) Arduino Pro Mini pins. Pay attention to the I2C bus pull up resistors. This experiment used 10K pull up resistors. However, you can use lower values.

No front-end was added to this receiver. However, you will be surprised with the its performance. You can connect to the audio output a mono or stereo amplifier or an earphone to listen to the radio. On article How to Build an Arduino-Controlled AM/FM/SW Radio [May 26, 2016], Mr. Raymond Genovese, suggests a better SI4844 setup, including a RF amplifier.

Another good source is the Silicon Labs Document AN602 “Si4822/26/27/40/44 ANTENNA, SCHEMATIC, LAYOUT, AND DESIGN GUIDELINES” Rev 0.3. This document also suggests better circuits. Check the AN602 pages: 8, 9 and 10 .

Arduino Pro Mini 3.3V and SI4844 connections

The table below shows the pin connections between the Si4844 and Arduino Pro Mini.

SI4844 pin	Arduino pin	Description
2	2	Arduino interrupt pin
15	12	Regurlar arduino digital pin used to RESET control
16	A4 (SDA)	I2C bus (Data)
17	A5 (SCL)	I2C bus (Clock)

OLED	Arduino pin
SDA	A4
CLK	D5

Buttons	Arduino pin
BAND_UP	8
BAND_DOWN	9
VOL_UP	10
VOL_DOWN	11

Schematic with Arduino Nano 5V and LCD16x02

This circuit uses the Arduino Nano or UNO, LCD16-02 with SI4844 device. Arduino Nano and the LCD16x02 operate with 5V. So, these two devices can be connected direct. However, you need a bi-directonal logic converter to connect the Arduino Nano or UNO to the SI4844 device. The schematic below shows the circuit with Arduino Nano 5V and LCD16x02. You can use the SI4844 minimal circuit as SI4844 setup reference. It is important to say if you have an LCD that operates with 3.3V, you can use Arduino Pro Mini or other similar that also operates with 3.3V. In this case, you do not need any bidirectional converter strategy.

The schematic below shows a suggestion to the bi-directional converter strategy.

It is important to say that a voltage divider will work for the Si4844 RST pin. However, for the I2C bus as well as the SI4844 IRQ pin, this approach may not work.

See also: Bi-Directional Logic Level Converter Hookup Guide for more details.

Once again, it is important to emphasize that there is currently an abundance of low-cost boards that will work safely with SI48XX devices without the need for a bidirectional level converter. Consider using other boards instead of an Arduino Nano or Uno, such as those based on the LGT8F328, ESP32, ESP8266, RPi PICO, and STM32.

Arduino Nano, LCD16x02, Push Buttons and SI4844 pin connections

You will find two versions of LCD16x2 on the market. The most common 5V version and the 3.3V version. The most direct way to use the SI4844 is to select the components that operate with the same working voltage. Otherwise, you must use some type of voltage conversion strategy.

SI4844 pin	Arduino pin	Description
2	2	Arduino interrupt pin
15	12	Arduino A0 (Digital pin 14) for SI4844 RESET
16	A4 (SDA)	I2C bus (Data)
17	A5 (SCL)	I2C bus (Clock)

LCD 16x02	Arduino pin
D4	D7	Arduino Digital Pin 7
D5	D6	Arduino Digital Pin 6
D6	D5	Arduino Digital pin 5
D7	D4	Arduino Digital Pin 4
RS	D3	Arduino Digital Pin 3 for LCD RESET controle
E/ENA	D13	Arduino Digital Pin 13
RW & VSS & K	GND
A & VDD	+Vcc
VO		(see 10K tripot connection)

Buttons	Arduino pin
BAND_UP	8
BAND_DOWN	9
VOL_UP	10
VOL_DOWN	11

Attention: If you are not using an Arduino Pro Mini, pay attention to the appropriated Arduino pinout to select the correct interrupt (IRQ), RST, SDIO and SCLK pins. The table below shows some Arduino board pinout.

Board	InterrupT (IRQ) Pins	I2C / TWI pins
328-based (Nano, Mini or Uno)	D2 and D3	A4 (SDA/SDIO), A5 (SCL/SCLK)
Mega	2, 3, 18, 19, 20 and 21	20 (SDA/SDIO), 21 (SCL/SCLK)
32u4-based (Micro, Leonardo or Yum)	0, 1, 2, 3 and 7	2 (SDA/SDIO), 3 (SCL/SCLK)
Zero	all digital pins except pin 4	D8 (SDA/SDIO) and D9 (SCL/SCLK)
Due	all digital pins	20 (SDA/SDIO), 21 (SCL/SCLK)
101	all digital pins. Only pins 2, 5, 7, 8, 10, 11, 12, 13 work with CHANGE

Again, pay attention to the operating voltage of the Arduino that you will use. The SI4844 device works with +3.3V. See Making the Si4844 works with 5V Arduino UNO or similar if you itend to use a 5V Arduino board.

Parts (for OLED and LCD16x02 versions)

Parts list used by the minimal schematic

Part	Description
IC1	Si4844-A10 radio receiver
Arduino	Arduino Pro Mini, 3.3V, 8MHz for OLED version or Nano for LCD16x02 version
Bi-Directional module	Only if you are using the Arduino Nano or Uno
C1	22pF ceramic capacitor
C2	22pF ceramic capacitor
C3	100nF ceramic capacitor
C4	4.7uF Electrolytic or ceramic capacitor
C5	4.7uF Electrolytic or ceramic capacitor
C6	100nF ceramic capacitor
C7	470nF ceramic capacitor
R1	3.3K ~ 10K resistor
R2	3.3K ~ 10K resistor
R3	100K linear potentiometer
L1	ferrite AM antenna
L2	100mH
Y1	32.768 kHz crystal
S1…S4	4 push buttons

Photos

SI4844 soldered on adapter

It was a bit hard to solder the Si4844 on adapter. However, by using a electronic magnifier it was possible.

prototyping

OLED/I2C and Arduino Pro Mini

LCD16x02 5V and Arduino Nano

Playing with Arduino UNO or Pro Mini 5v and SI4844

During my tests, I have used the TCA9548A as an alternative to regular bi-directional converter on I2C bus. Actually the TCA9548A is an I2C Multiplexer Breakout Board 8 Channel Expansion Board, but you can use it as a bi-directional converter for I2C bus. Some features:

1. 1-to-8 Bidirectional Translating Switches
2. I2C Bus and SMBus Compatible
3. Active-Low Reset Input
4. Three Address Pins, Allowing up to Eight TCA9548A Devices on the I2C Bus
5. Channel Selection Through an I2C Bus, In Any Combination
6. Power Up With All Switch Channels Deselected
7. Low RON Switches
8. Allows Voltage-Level Translation Between 1.8-V, 2.5-V, 3.3-V, and 5-V Buses
9. Supports Hot Insertion
10. Low Standby Current
11. Operating Power-Supply Voltage Range of 1.65 V to 5.5 V
12. 5-V Tolerant Inputs
13. 0- to 400-kHz Clock Frequency

You can use a voltage divider for reset (RST) and connect the IRQ direct to the Arduino pin 2 (configures as input).

API Documentation

See:

1. API Documentation
2. Example POC
3. Example ESP32
4. Example ESP8266

References

1. Si48XX ATDD PROGRAMMING GUIDE
2. BROADCAST ANALOG TUNING DIGITAL DISPLAY AM/FM/SW RADIO RECEIVER
3. Si4822/26/27/40/44 ANTENNA, SCHEMATIC, LAYOUT, AND DESIGN GUIDELINES
4. How to Build an Arduino-Controlled AM/FM/SW Radio
5. I2C bi-directional level shifter
6. Making the Si4844 works with 5V Arduino UNO or similar

Examples

On examples folder you will find some sketches that might help you in your project.

Firmware Information

The SI4844_FIRMWARE.ino start the radio on FM Band and shows the SI4844 firmware information.

Minimal Radio with SI4844 (SI4844_MINIMAL)

The SI4844_MINIMAL.ino is a sketch with just 35 lines. It is enough to make a simple radio based on SI4844.

Proof of Concept

The SI4844_POC.ino is a proof of concept for SI4844 controlled by Arduino and the SI4844 Library. This Arduino Sketch only works on your IDE (Arduino IDE). However, you can replace the Serial Monitor functions that deal the SI4844 and arduino with functions that will manipulate the LCD, encoder and push buttons appropriated for your project.

Extended SW band frequency ranges from 2.3–5.6 MHz and 22–28.5 MHz

The sketch SI4844_CUSTOM_BAND.ino shows how to extend a SW band frequency ranges. You can define band from from 2.3–5.6 MHz and 22–28.5 MHz.

SI4844 with OLED and buttons

The sketch SI4844_01_OLED.ino shows an example of using an I2C OLED display.

The schematic below shows how to insert the OLED and button on the original schematic.

SI4844 with Nano and LCD16x02

The sketch SI4844_02_LCD16x02.ino shows an example of using the traditional LCD16x02.

The schematic below shows the circuit used with this sketch.

Sound Control

The sketch SI4844_BASS_TREBLE.ino shows how to use sound control (treble, bass, mute etc).

Videos

1. Biblioteca Arduino para o Rádio SI4844 FM AM SW da Silicon Labs
2. Prova de Conceito com SI4844 e Arduino (vídeo sobre este projeto)

Projects in which this library is used

• si4844 机械调谐 数字显示全波段收音机