Intermediate
20 min

Achieve communication with external devices over telephone lines or data networks with CMX869B and ATmega1284

Low-power modem solution for EPOS (Electronic Point of Sale) terminals and telephone-based systems

EPOS Module Click with EasyAVR v7

Published Sep 23, 2024

Click board™

EPOS Module Click

Dev. board

EasyAVR v7

Compiler

NECTO Studio

MCU

ATmega1284

Enable secure, low-power modem communication for EPOS terminals and remote systems ideal for reliable data transfer in industrial control and security applications

A

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Hardware Overview

How does it work?

EPOS Module Click is based on the CMX869B, a multi-standard v.32 bis modem from CML Micro, which supports multiple protocols while offering low power consumption. This low-power modem solution is designed for applications involving EPOS (Electronic Point of Sale) terminals and telephone-based systems. The CMX869B supports standards such as ITU V.32 bis, V.22 bis, V.22, V.21, and Bell 202 and 103, making it adaptable for numerous communication scenarios. It operates at data rates of up to 14.400bps and features automatic fallback to 4.800bps, with capabilities like retrain rate re-negotiation and automatic detection of V.22 and V.22 bis modems. This Click board™ is ideal for use in EPOS terminals, telephone telemetry systems, remote utility meter reading, security systems, industrial control, and other applications. In addition to its robust modem

functions, the CMX869B includes a high-quality DTMF (Dual-Tone Multi-Frequency) encoder and decoder, making it suitable for managing call signaling and detection in telephone systems. The modem can also transmit and detect user-programmed single and dual-tone signals, as well as handle modem calling and answering tones, ensuring compatibility with various proprietary communication protocols beyond standard modem operations. The Click board™ also offers a fully isolated EPOS/telephone-based connection, thanks to its built-in P1200 transformer, which ensures smooth communication while providing complete electrical isolation. Data and control exchanges between the CMX869B and the host MCU are made through a C-BUS interface, compatible with a standard 4-wire SPI interface of the mikroBUS™ socket. The board also uses the mikroBUS™

socket's IRQ pin for interrupt requests related to call states like busy, dialing, and connected statuses, a red RING LED to indicate ringing signals, and a blue HOOK LED that serves as a hookswitch indicator to manage the line interface's connectivity status (0-OFF, 1-ON). An additional feature of the CMX869B is the Powersave mode, which conserves energy by deactivating all circuits except the essential C-BUS (SPI) interface. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it comes equipped with a library containing functions and an example code that can be used as a reference for further development.

EPOS Module Click hardware overview image

Features overview

Development board

EasyAVR v7 is the seventh generation of AVR development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 16-bit AVR microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyAVR v7 allows you to connect accessory boards, sensors, and custom electronics more

efficiently than ever. Each part of the EasyAVR v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B)

connector. Communication options such as USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets which cover a wide range of 16-bit AVR MCUs. EasyAVR v7 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

EasyAVR v7 horizontal image

Microcontroller Overview

MCU Card / MCU

ATmega1284

Architecture

AVR

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

40

RAM (Bytes)

16384

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
SPI Chip Select
PA5
CS
SPI Clock
PB7
SCK
SPI Data OUT
PB6
MISO
SPI Data IN
PB5
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Interrupt Request
PD2
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
NC
NC
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

EPOS Module Click Schematic schematic

Step by step

Project assembly

EasyAVR v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyAVR v7 as your development board.

EasyAVR v7 front image hardware assembly
GNSS2 Click front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
EasyAVR v7 Access DIP MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
NECTO Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto DIP image step 7 hardware assembly
EasyPIC PRO v7a Display Selection Necto Step hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image hardware assembly

Track your results in real time

Application Output

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for EPOS Module Click driver.

Key functions:

  • eposmodule_handshake_init - This function performs a handshake init which resets the device settings to default.

  • eposmodule_dial - This function dials the selected number by alternating between DTMF and No-tone.

  • eposmodule_send_message - This function sends an array of bytes via V.23 FSK 1200bps modem in start-stop 8.1 mode.

Open Source

Code example

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * @file main.c
 * @brief EPOS Module Click example
 *
 * # Description
 * This example demonstrates the use of EPOS Module Click board by showing
 * the communication between the two Click boards connected to PBX system.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and logger, and displays the selected application mode.
 *
 * ## Application Task
 * Dialing application mode:
 * - Resets the device settings and dials the selected number. If a call is answered
 * it starts sending desired messages every couple of seconds with constantly checking
 * if a call is still in progress or it's terminated from the other side.
 * Answering application mode:
 * - Resets the device settings and waits for an incoming call indication, answers the call,
 * and waits for a desired number of messages. The call is terminated after all messages
 * are received successfully.
 *
 * @note
 * We have used a Yeastar S20 VoIP PBX system for the test, where the Click boards are
 * connected to ports 1 and 2 configured as FXS extension with numbers 1000 and 1001 (dialer).
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "eposmodule.h"

// Demo aplication selection macros
#define APP_DIALING                 0
#define APP_ANSWERING               1
#define DEMO_APP                    APP_DIALING

// Dialing application settings - a dial number and text to send (must end with CRLF - \r\n)
#define DIAL_NUMBER                 "1000"
#define TEXT_TO_SEND                "MIKROE - EPOS Module Click\r\n"

// Answering application settings - a number of successfully received messages before call termination
#define NUM_MESSAGES                5u

static eposmodule_t eposmodule;
static log_t logger;

void application_init ( void )
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    eposmodule_cfg_t eposmodule_cfg;  /**< Click config object. */

    /** 
     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
     */
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, " Application Init " );

    // Click initialization.
    eposmodule_cfg_setup( &eposmodule_cfg );
    EPOSMODULE_MAP_MIKROBUS( eposmodule_cfg, MIKROBUS_1 );
    if ( SPI_MASTER_ERROR == eposmodule_init( &eposmodule, &eposmodule_cfg ) )
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }

#if ( DEMO_APP == APP_DIALING )
    log_printf( &logger, " Application Mode: Dialing\r\n" );
#elif ( DEMO_APP == APP_ANSWERING )
    log_printf( &logger, " Application Mode: Answering\r\n" );
#else
    #error "Selected application mode is not supported!"
#endif
    
    log_info( &logger, " Application Task " );
}

void application_task ( void )
{
    uint8_t state = EPOSMODULE_STATE_IDLE;
    uint32_t time_cnt = 0;
    uint8_t msg_cnt = 0;

    eposmodule_handshake_init ( &eposmodule );

#if ( DEMO_APP == APP_DIALING )
    log_printf( &logger, "\r\n Hook OFF\r\n" );
    eposmodule_hook_off ( &eposmodule );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " Dial: %s\r\n", ( char * ) DIAL_NUMBER );
    eposmodule_dial ( &eposmodule, DIAL_NUMBER );
    eposmodule.rx_mode &= EPOSMODULE_RX_LEVEL_MASK; // No change in rx level setting
    eposmodule.rx_mode |= ( EPOSMODULE_RX_MODE_DTMF_TONES | EPOSMODULE_RX_TONE_DETECT_CALL_PROG );
    eposmodule_set_receive_mode ( &eposmodule, eposmodule.rx_mode );
    for ( ; ; )
    {
        Delay_ms ( 1 );
        if ( !eposmodule_get_irq_pin ( &eposmodule ) )
        {
            time_cnt = 0;
            state = EPOSMODULE_STATE_IRQ_SET;
        }
        if ( ( EPOSMODULE_STATE_IRQ_SET == state ) && !eposmodule_call_progress ( &eposmodule ) )
        {
            if ( time_cnt < EPOSMODULE_TIMING_BUSY )
            {
                log_printf( &logger, " Busy\r\n" );
                break;
            }
            else if ( time_cnt < EPOSMODULE_TIMING_DISCONNECTED )
            {
                log_printf( &logger, " Disconnected\r\n" );
                break;
            }
            else if ( time_cnt < EPOSMODULE_TIMING_RINGING )
            {
                log_printf( &logger, " Ringing\r\n" );
                state = EPOSMODULE_STATE_RINGING;
            }
        }
        if ( ( EPOSMODULE_STATE_RINGING == state ) && ( time_cnt > EPOSMODULE_TIMING_CALL_PROGRESS ) )
        {
            log_printf( &logger, " Call in progress\r\n" );
            state = EPOSMODULE_STATE_CALL_IN_PROGRESS;
            time_cnt = 0;
        }
        if ( ( EPOSMODULE_STATE_CALL_IN_PROGRESS == state ) && !( time_cnt % EPOSMODULE_TIMING_SEND_MESSAGE ) )
        {
            log_printf( &logger, " Send message %u\r\n", ( uint16_t ) msg_cnt++ );
            eposmodule_send_message ( &eposmodule, TEXT_TO_SEND, strlen ( TEXT_TO_SEND ) );
        }
        if ( time_cnt++ > EPOSMODULE_TIMEOUT_CALL_PROGRESS )
        {
            log_printf( &logger, " Timeout\r\n" );
            break;
        }
    }
    log_printf( &logger, " Hook ON\r\n" );
    eposmodule_hook_on ( &eposmodule );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
#elif ( DEMO_APP == APP_ANSWERING )
    uint8_t rx_data = 0;
    uint8_t msg_end_buff[ 2 ] = { 0 };

    log_printf( &logger, "\r\n Waiting for a call...\r\n" );

    while ( !eposmodule_ring_detect ( &eposmodule ) );

    Delay_ms ( 1000 );
    log_printf( &logger, " Hook OFF\r\n" );
    eposmodule_hook_off ( &eposmodule );
    Delay_ms ( 1000 );
    log_printf( &logger, " Waiting for %u messages...\r\n", ( uint16_t ) NUM_MESSAGES );
    eposmodule.rx_mode &= EPOSMODULE_RX_LEVEL_MASK; // No change in rx level setting
    eposmodule.rx_mode |= ( EPOSMODULE_RX_MODE_V23_FSK_1200 | EPOSMODULE_RX_DATA_FORMAT_SS_NO_OVS | 
                            EPOSMODULE_RX_DATA_PARITY_8_NO_PAR );
    eposmodule_set_receive_mode ( &eposmodule, eposmodule.rx_mode );

    for ( ; ; )
    {
        Delay_ms ( 1 );
        if ( !eposmodule_get_irq_pin ( &eposmodule ) )
        {
            if ( EPOSMODULE_STATE_IDLE != state )
            {
                log_printf( &logger, "\r\n Disconnected\r\n" );
                break;
            }
            log_printf( &logger, " Message %u: ", ( uint16_t ) msg_cnt );
            state = EPOSMODULE_STATE_IRQ_SET;
            time_cnt = 0;
        }
        if ( ( EPOSMODULE_STATE_IRQ_SET == state ) && !( time_cnt % EPOSMODULE_TIMING_RX_READY ) )
        {
            if ( eposmodule_unscram_1s_det ( &eposmodule ) && eposmodule_rx_ready ( &eposmodule ) )
            {
                eposmodule_receive_data ( &eposmodule, &rx_data );
                if ( ( ( ' ' <= rx_data ) && ( '~' >= rx_data ) ) || 
                     ( '\r' == rx_data ) || ( '\n' == rx_data ) )
                {
                    log_printf( &logger, "%c", ( char ) rx_data );
                }
                if ( '\r' == rx_data )
                {
                    msg_end_buff[ 0 ] = rx_data;
                }
                else if ( '\n' == rx_data )
                {
                    msg_end_buff[ 1 ] = rx_data;
                }
                else
                {
                    msg_end_buff[ 0 ] = 0;
                    msg_end_buff[ 1 ] = 0;
                }
            }
            if ( ( '\r' == msg_end_buff[ 0 ] ) && ( '\n' == msg_end_buff[ 1 ] ) )
            {
                msg_end_buff[ 0 ] = 0;
                msg_end_buff[ 1 ] = 0;
                state = EPOSMODULE_STATE_IDLE;
                if ( NUM_MESSAGES == ++msg_cnt )
                {
                    Delay_ms ( 100 );
                    log_printf( &logger, " Terminate call\r\n" );
                    Delay_ms ( 100 );
                    break;
                }
            }
        }
        if ( time_cnt++ > EPOSMODULE_TIMING_WAIT_FOR_MESSAGE )
        {
            log_printf( &logger, "\r\n Timeout\r\n" );
            break;
        }
    }
    log_printf( &logger, " Hook ON\r\n" );
    eposmodule_hook_on ( &eposmodule );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
#endif
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}

// ------------------------------------------------------------------------ END

Additional Support

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