AKC695X

Arduino Library for the AKC695X devices

View on GitHub

PU2CLR AKC695X Arduino Library

This is an Arduino Library to control the AKC695X / M695X DSP radio devices.

This library was built based on AKC6955 stereo FM / TV / MW / SW / LW digital tuning radio document from “AKC technology”. Others sources help the author to build this library. You can check these sources on References.

The PU2CLR AKC695X Arduino Library also intend to be used on all members of the AKC695X family with I²C bus interface respecting, of course, the features available for each IC version. Please, check the Datasheet of the divice before starting your project. Finally, it can be freely distributed using the MIT Free Software model.

Copyright (c) 2020 Ricardo Lima Caratti.

Contact: pu2clr@gmail.com.

Be a member of Facebook group DSP receivers for hobbyists

Contents

  1. Preface
  2. Your support is important
  3. Library Features
  4. MIT License
  5. Library Installation
  6. About AKC695X / M695X DSP radio
    1. Register setup
    2. Register operations
    3. AKC695X Pin definitions
  7. SCHEMATIC
  8. API Documentation
  9. Source code - Arduino sketch examples
  10. Videos
  11. References
  12. Commercial receivers based on AKC6955

Preface

AKC695X device family offer versatile FM/MW/SW/LW receiver solution by reducing the external components usually found in regular receivers. This device family will surprise hobbyists and experimenters with its simplicity to build FM and AM (LW, MW, SW) receivers.

There are currently some receivers based on DSP technology. The KT0915 and SI4735 devices are some examples widely disseminated in the market. This library was developed with the purpose of expanding the alternatives to hobbyists and radio listeners.

In this document you will see Arduino source codes, schematics, examples and tips to help you to build a receiver based on Arduino board and AKC695X devices. The project and examples shown here do not intend to be a real receiver for exigent listener. However, it is possible to start with it and after add some improvements. On the other hand, with the simple circuits shown here, the experimenter may be surprised with the AKC695X performance.


Presentation video

AKC6955 controlled by a standalone ATmega328 and LCD16x2

See also

More Arduino Projects developed by author

Your support is important

If you would like to support this library development, consider joining this project via Github. Alternatively, make suggestions on new features and report errors if you find them. Thank you!


Library Features

This library uses the I²C communication protocol and implements most of the functions offered by the AKC695X (BROADCAST AM / FM / SW / LW RADIO RECEIVER).

The main features of this library are listed below.

  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 AKC6955 stereo FM / TV / MW / SW / LW digital tuning radio;
  3. C++ Language and Object-oriented programming. You can easily extend the AKC695X class by adding more functionalities;
  4. Available on Arduino IDE (via Manage Libraries). Easy to install and use;
  5. Cross-platform. You can compile and run this library on most of board available on Arduino IDE (Examples: ATtiny85, boards based on ATmega328 and ATmega-32u4, ATmega2560, ARM Cortex, STM32, Arduino DUE, ESP32 and more);
  6. Simplifies projects based on AKC695X IC family with support to I²C;
  7. Seeking function support;
  8. Support to 32.768kHz and 12MHz crystal oscillators;
  9. Support to audio controlled by the MCU (Arduino) or potentiometer;
  10. Real tim FM stereo or mono indicator;
  11. FM stereo or mono selecting;
  12. Real time signal level reading;
  13. Real time AM and FM carrier to noise ratio information (dB).
  14. Bandwidth selection for FM;
  15. Custom band support;
  16. More than 40 functions implemented.

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.

Thanks

Library Installation

You can install this library on your Arduino environment using different methods.

Installing via Arduino IDE

The video below shows how to install the PU2CLR AKC695X Arduino Library from your Arduino IDE.

PU2CLR AKC695X Arduino Library Installation

Installing via the repository

With this approach, you will have the most current version of the library. However, it may not be the most stable version. This is because the current version is always in development. Prefer releases. Do you need some old version (release) of this library? If yes, check here.

First, you have to download this library in zip format. The figures below show that.

Downloading from AKC695X PU2CLR Arduino Library repository

First step

Installing from this repository


Last step

Installing from this repository


After download, unzip the AKC695X-master.zip file in your Arduino Library folder. Check this folder path below.

About AKC695X / M695X DSP radio

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 AKC6969 work on LW, MW and SW. On FM mode they work from 64MHz to 222MHz.

AKC695X features

The table below shows some AKC695X devices family features.

Feature AKC6951 AKC6955 AKC6959sx
stand by 30 ~ 230MHz Any frequency FM demodulation X X X
stand by 0.15 ~ 30MHz Any frequency AM demodulation X X X
Preset FM band ( 64 ~ 108 MHz ) X X X
stand by TV1 audio( 56.25 ~ 91.75 MHz ) X X X
stand by TV2 audio( 174.75 ~ 222.25 MHz ) X X X
Presets wave band ( 520 ~ 1730 kHz ) X X X
Preset shortwave band ( 3.2 ~ 21.9 MHz )   X X
Preset long-wave band ( 150 ~ 285 kHz ) X X X
Custom support band   X X
It supports a wide supply voltage range: 2.0V ~ 4.5V X X X
stand by 32.768kHz & 12MHz Passive mode crystal reference clock and Pin X X X
Integrated audio amplifier (maximum power differential 0.5W ) X X X
Two kinds of control volume: volume potentiometer and the volume register X X X
Two kinds of de-emphasis modes: 50us / 75us X X X
Support tuning lamp function X X X
The audio output may be in phase, may be inverted output X X X
Support for stereo line input X X X
Support low-power standby mode, 3V When power consumption 10uA X X X
Internal integrated PLL X X X
Intelligent frequency control X X X
AGC X X X
Precise digital demodulation X X X
Smart mute function X X X
SW Increased tracking filter, greatly improving SW Audibility   X X
MW Precise tuning adaptive front end X X X
FM Subwoofer X X X
integrated LDO X X X
According to the battery voltage, automatically adjust the volume X X X
Pb-free / RoHS complian X X X

Sources: AKC6951, AKC6955 and AKC6959sx Datasheets.

ATTENTION: The AKC6952 and AKC6959 do not have I²C interface. So, they will not work with this library. Try AKC6951, AKC6955 or AKC6959sx.

Registers setup

This library uses the I²C protocols to read and write AKC695X registers. In this context, registers are memory position into the device.

The first 13 registers, you can use to change the behavior of the device. They are read and write registers. The registers from 20 to 27, can be used to get the current device status. They are read only registers.

By writing and reading these register, you can control the AKC695X devices.

Register operations

By using the registers 0 to 13, you can change the band, set the frequency, set the channel space, set the audio behavior and volume, set a custom band and more. The file AKC695X.h has details about the all registers used in the library. Also, you can read the API Documentation to know more about AKC695X registers.

There is no information about the register 10 and the registers 14 to 19 in the documentation used to develop this library.

To represent the information stored in the AKC695X registers, this library used the resources of the C / C ++ language: union, struct and typedef. This way, the user of this library will be able to customize it easily.

This approach is shown below for the registers 0, 1, 2 and 3.

Table Reg0

Reg0: configure register 0 (default: 0x4c) Address - Type 0x00 (RW)

BIT Label Default Function Description
7 power_on 0 1 = On; 0 = Off
6 fm_en 1 1 = FM; 0 = AM
5 tune 0 1 = Trigger tune process. The STC bit is set high when the tune operation completes
4 seek 0 1 = Trigger tune process. The STC bit is set high when the tune operation completes
3 seekup 1 1 = Seek up; 0 = Seek down
2 mute 1 0 = Normal operation; 1 = Mute L / R
1:0 rsv 00 Debug use, do not change this value using

Source: AKC6955 stereo FM / TV / MW / SW / LW digital tuning radio

Be aware that the table above presents the data in order of the most significant bits to the least significant bits. In C/C++ representation of that data will be inverted. See the C/C++ code below.

Data representation in C/C++ for the register 0
typedef union {
    struct
    {
        uint8_t rsv : 2;      //!< Reserved - Debug use, do not change this value using
        uint8_t mute : 1;     //!< 1 - Mute L / R channel 0 - Normal operation
        uint8_t seekup : 1;   //!< Seek direction control bit. 0 = Seek down;  1 = Seek up
        uint8_t seek : 1;     //!< 0-> 1 Trigger tune process The STC bit is set high when the tune operation completes.
        uint8_t tune : 1;     //!< 0-> 1 Trigger tune process The STC bit is set high when the tune operation completes.
        uint8_t fm_en : 1;    //!< 1 = FM mode;  0 = AM mode
        uint8_t power_on : 1; //!< 1 = Chip on; 0 = Chip off
    } refined;
    uint8_t raw;
} akc595x_reg0;

It is important to say that the code above does not necessarily generate extra machine code. Much more than that, the code above guides the compiler on how to operate with the AKC695X bits stored into its registers. In this case register 0. If you have some experience in C/C++, you will know when you can use this approach instead direct bit manipulation and vice-versa.

The code below is an example of how this data structure can be used.

void AKC695X::powerOn(uint8_t fm_en, uint8_t tune, uint8_t mute, uint8_t seek, uint8_t seekup)
{
    akc595x_reg0 reg0;

    reg0.refined.power_on = 1;
    reg0.refined.rsv = 0;
    reg0.refined.fm_en = fm_en;
    reg0.refined.mute = mute;
    reg0.refined.seek = seek;
    reg0.refined.seekup = seekup;
    reg0.refined.tune = tune;

    setRegister(REG00, reg0.raw);

}

Table Reg1

Reg1: configure register 1 (default: 0x10) Address - Type 0x01 (RW)

BIT Label Default Function Description
7:3 amband 0x2 see table Table Reg1 amband
2:0 fmband 0x00 see table Table Reg1 fmband

Source: AKC6955 stereo FM / TV / MW / SW / LW digital tuning radio

Data representation in C/C++ for the register 1
typedef union {
    struct
    {
        uint8_t fmband : 3; //!<
        uint8_t amband : 4; //!<
    } refined;
    uint8_t raw;
} akc595x_reg1;

The code below is an example of how the akc595x_reg1 can be used.

      .
      .
    akc595x_reg1 reg1;
      .
      .
    reg1.raw = 0;
    reg1.refined.fmband =  fm_band; // Selects the band will be used for FM (see fm band table)
    setRegister(REG01, reg1.raw);
      . 
      .
Table Reg1 amband

The table below can help you to select the right band and its frequency limits. You might need to use it in your Arduino sketch.

amband value N# Description
00000 0 LW, 0.15 ~ 0.285, 3K station search
00001 1 MW1, 0.52 ~ 1.71, 5K station search
00010 2 MW2, 0.522 ~ 1.62, 9K station search
00011 3 MW3, 0.52 ~ 1.71, 10K station search
00100 4 SW1, 4.7 ~ 10, 5K station search
00101 5 SW2, 3.2 ~ 4.1, 5K station search
00110 6 SW3, 4.7 ~ 5.6, 5K station search
00111 7 SW4, 5.7 ~ 6.4, 5K station search
01000 8 SW5, 6.8 ~ 7.6, 5K station search
01001 9 SW6, 9.2 ~ 10, 5K station search
01010 10 SW7, 11.4 ~ 12.2, 5K station search
01011 11 SW8, 13.5 ~ 14.3
01100 12 SW9, 15 ~ 15.9
01101 13 SW10, 17.4 ~ 17.9
01110 14 SW11, 18.9 ~ 19.7, 5K station search
01111 15 SW12, 21.4 ~ 21.9, 5K station search
10000 16 SW13, 11.4 ~ 17.9, 5K station search
10010 17 MW4, 0.52 to 1.73, 5K station search
Other 18+ custom band, station search interval = 3K
Table Reg1 fmband
fmband value N# Description
000 0 FM1,87 ~ 108, station search space specified intervals
001 1 FM2,76 ~ 108, station search space specified intervals
010 2 FM3,70 ~ 93, with a space station search interval set
011 3 FM4,76 ~ 90, Tuning predetermined space intervals
100 4 FM5,64 ~ 88, with a space station search interval set
101 5 TV1,56.25 ~ 91.75, station search space specified intervals
110 6 TV2, 174.75 ~ 222.25, found
111 7 sets predetermined space intervals, custom FM, station search space specified intervals

Table Reg2 and Reg3

The registers 2 and 3 are used together. The tuning frequency is obtained by calculation. The formula is described below.

Reg2

BIT Label Default Function Description
7 rsv 0 Reserved for internal use.
6 ref_32k_mo 1 1 = 32.768 crystal; 0 = 12MHz crystal
5 Mode3k 0 1 = 3K custom channel number as the AM mode; 0 = custom channel number pattern 5K
4:0 Channel 0x0A The higher 5 bits of the channel number. See comments [ˆ1] and [ˆ2]
Data representation in C/C++ for the register 2
typedef union {
    struct
    {
        uint8_t channel : 5;      //!< (0:4) - 5 most significant bits that represents the channel (see reg3)
        uint8_t mode3k : 1;       //!< (5)   - 1 = 3K; 0 = 5K
        uint8_t ref_32k_mode : 1; //!< (6)   - 1 = 32K ref. crystal clock; 0 = 12MHz ref crystal clock
        uint8_t rsv : 1;          //!< (7)   - Reserved - Debug use, do not change this value using
    } refined;
    uint8_t raw;
} akc595x_reg2;
Reg3
BIT Label Default Function Description
7:0 rsv 0xC8 The lower 8 bits of the channel number. See comment [ˆ1]

[ˆ1]

  1. On FM mode: Channel Freq = 25kHz * CHAN + 30MHz;
  2. On AM mode:
    • when 5K channel number pattern, Channel Freq = 5kHz * CHAN
    • when 3K channel number pattern, Channel Freq = 3kHz * CHAN.

[ˆ2] If the MCU is working with MW2 (see table Table Reg1 amband), the channel number has to be a multiple of three. Otherwise, the radio will be a mess.

Data representation in C/C++ for the register 3
typedef uint8_t akc595x_reg3;


See AKC695x.cpp methods setFM, setAM and setFrequency to know how the akc595x_reg2 and akc595x_reg2 work.

Click here to read the complete API Documentation



Schematic

The main porpuse of this circuit is testing de AKC695X Arduino Library. It does not intend to be a real receiver for exigent listener. However, it is possible to start with it and after add some improvements. On the other hand, with this simple circuit, the experimenter may be surprised with its performance.

The figure below shows the basic schematic of the AKC695X and Arduino Pro Mini 3.3V, 8MHz.

Basic Schematic

The schematic below shows the AKC6955 controlled by a standalone ATmega328 with a LCD16X2

Basic Schematic 2

Arduino Pro mini 3.3V/8MHz or standalone Atmega328 and AKC6955, encoder and LCD16x2

Device name Device Pin / Description Arduino Pin
LCD 16x2 or 20x4 (3.3V)    
  D4 D7
  D5 D6
  D6 D5
  D7 D4
  RS D12
  E/ENA D13
  RW & VSS & K (16) GND
  A (15) & VDD +Vcc
  VO (see 20K tripot connection) ———
AKC6955    
  RESET (pin 5) 9
  SDIO (pin 6) A4
  SCLK (pin 7) A5
Encoder    
  A 2
  B 3
  PUSH BUTTON (encoder) A0/14

Component parts

Name / Label Description
AKC6955 SSOP24 DSP receiver from AKC. You also can use AKC5951 (just FM and AM/MW) or AKC6959sx
Arduino Board It can be an Atmega based board, SMT32, ESP32, Attiny or another compatible Arduino board
Y1 32.32.768kHz or 12MHz crystal oscillator. By default this library uses 32.768kHz. But, you can set it to deal with 12MHz crystal. See API Documentation.
C1 and C2 22pF Ceramic or Tantalum capacitor
C3 470uF Electrolytic capacitor
C4 1nF Ceramic or Tantalum capacitor
C4 1nF Ceramic or Tantalum capacitor
C5 and C8 100nF Ceramic or Tantalum capacitor
C6 100pF Ceramic or Tantalum capacitor
C7 3nF Ceramic or Tantalum capacitor
C9 22uF Electrolytic capacitor
R1 10K resistor
R2 22K resisto. This value is not critical. Use something closer to 25K
R3 4.7K resistor. This value is not critical. Use something closer to 5K
LED1 regular LED
L1 Ferrite Rod Coil for LW and MW. It is very common in old medium wave receivers

AKC695X Pin definitions

The figure and table below show the pin description of the AKC6951 and AKC6955.

AKC6951(55) pin out

Pin Name Description
1 oscin Bonding or passive 32.768K 12MHz crystal to ground, or receive an external clock reference signal
2 oscout Passive other end connected to the crystal, when connected to an external clock, this pin floating
3 gnd Close to ground
4 tund Radio lock indicator pin, connected directly to the light emitting diode; Tuning the MCU software when the pin may also be used as a stop sign
5 p_on On-chip power switch, high input power chip; the chip down in a low-power standby state, power consumption of approximately 10uA
6 sclk 2C clock signal input
7 sdio I²C bidirectional data signal input / output
8 inl External audio signal input L, proposes to add blocking capacitor 1uF
9 inr External audio input signal R, proposes to add blocking capacitor 1uF
10 vbat Then the power pins need to pay attention to the nearest ground 0.1uF decoupling capacitance to ground
11 lout Left channel audio output
12 gnd gnd
13 rout Right channel audio output
14 vref Precision 1.5V output pin, to provide a baseline volume potentiometer
15 vol Variable volume potentiometer connected end, the fixed end of a potentiometer directly connected to VREF, and the other end through a resistor to ground. The resistance ratio of the resistor and potentiometer as 1: 2
16 vbat Then the power pins need to pay attention to the nearest ground 0.1uF decoupling capacitance to ground
17 gnd Close to ground
18 mwinN MW and LW differential input signal
19 mwinP MW and LW differential input signal
20 swin Shortwave signal input terminal, note add blocking capacitor recommended 3nF
21 gnd Close to ground
22 fmin FM radio frequency signal input terminal, note add blocking capacitor, 100pF recommendations
23 ldocap Internal LDO output pin, nearest the need decoupling capacitors, recommendations 47uF
24 gnd Close to ground

Prototype Photos

Photo 01


Ponto 02


Photo 03


Photo 03


Videos

Receivers based on AKC695X / M695X

Troy reviews the Audiomax SRW-710S Full Review of the Tivdio V115 AM FM Shortwave portable receiver

Third-party projects using this library

References

Commercial receivers based on AKC6955