Modernize RS232 connections with MAX3232 and PIC32MX795F512L
Upgrading data transfer: The only UART-to-RS232 bridge you need
Published Oct 19, 2023
Click board™
RS232 Click
Dev Board
Explorer 16/32 development board
Compiler
NECTO Studio
MCU
PIC32MX795F512L
Efficient solution for incorporating RS-232 communication capabilities into various electronic projects and applications, including serial data exchange and modem communication
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Hardware Overview
How does it work?
RS232 Click is based on the MAX3232, a low-power, true RS-232 transceiver from Analog Devices. Several protection features improve the reliability of this device. It has up to ±15kV ESD protection, ensuring no electrical discharge damages the circuit on the input side. The MAX3232 has two receivers and two transmitter channels, and it is used to bridge the physical differences between the CMOS/TTL signal levels and RS-232 bus levels. While CMOS/TTL signal levels vary from 0V to 5V typically, RS-232 uses signal levels that range from ±5V up to ±15 V. Furthermore, the RS-232 equipment is required to withstand short circuits for any voltage, up to ±25V, during an indefinite time interval. MAX3232 IC uses two internal charge pumps to obtain required driving levels of ±5V on its transceiver sections.
This Click board™ offers two inputs and two outputs, which feature the CMOS/TTL logic levels. These lines can be used to either drive the RS-232 bus or receive the incoming data from the bus. Receivers convert the RS-232 signals to MCU-acceptable UART-type signals, while transmitters convert the MCU UART signal to RS-232 levels. Therefore, one input/output pair is routed to the UART pins of the mikroBUS™, allowing simplified operation by the host MCU, while another pair of input/output signals is routed via the J2 and J3 SMD jumpers and is used as the UART RTS and CTS. These pins are typically used for the UART communication with the hardware flow control. The jumpers are unpopulated by default. The MAX3232 device can maintain a 120kbps data rate with the worst-case scenario - load of 3kΩ in parallel with
1000pF, while the typical communication speed goes up to 232 kbps. The RS232 Click comes equipped with the SUB D connector, typically found on many devices that use the RS-232 interface, and can be used for connection directly to the RS-232 bus. RS232 uses a standard 2-Wire UART interface to communicate with the host MCU. If using it with soldered J2 and J3 jumpers, then you can use the UART RTS and CTS hardware flow control pins. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the PWR SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.
Features overview
Development board
Explorer 16/32 development board is a flexible and convenient development, demonstration, and testing platform for 16-bit PIC24 MCUs, dsPIC® DSCs, and 32-bit PIC32 MCUs from Microchip Technology. It features all the necessary hardware to develop and debug a complete embedded application. The board accepts Processor Plug-In Modules (PIMs) designed for the Explorer 16 or Explorer 16/32 development board for easy device swapping. In addition to the hardware features provided by the board, hardware expansion is possible through the use of PICtail™ Plus
daughter cards and mikroBUS™ accessory boards. Coupled with the integrated PICkit™-On-Board (PKOB), MPLAB ICD In-Circuit Debugger real-time debug facilities enable faster evaluation and prototyping of applications. This development board supports all the Explorer PIMs. However, not all PIMs are supported by the PKOB. To check the list of supported and unsupported PIMs, refer to the PICkit™ On-Board 3 (PKOB3) Support List. For PIMs not on the PKOB3 support list, use the JP1 or J14 connectors to program the device with a newer generation programming tool. Explorer 16/32
development board offers only the main board, allowing customization of the other necessary components. Choose your PIM based on MCUs and DSCs under consideration from a wide range of Processor Plug-In Modules. This board is optimal for customers migrating from Classic Explorer 16 to the new Explorer 16/32 platform, while all the necessary additional components like Processor Plug-In Modules and PICtail™ Plus Daughter Boards are already available.
Microcontroller Overview
MCU Card / MCU
Architecture
PIC32
MCU Memory (KB)
512
Silicon Vendor
Microchip
Pin count
100
RAM (Bytes)
131072
You complete me!
Accessories
DB9 Cable Female-to-Female (2m) cable is essential for establishing dependable serial data connections between devices. With its DB9 female connectors on both ends, this cable enables a seamless link between various equipment, such as computers, routers, switches, and other serial devices. Measuring 2 meters in length, it offers flexibility in arranging your setup without compromising data transmission quality. Crafted with precision, this cable ensures consistent and reliable data exchange, making it suitable for industrial applications, office environments, and home setups. Whether configuring networking equipment, accessing console ports, or utilizing serial peripherals, this cable's durable construction and robust connectors guarantee a stable connection. Simplify your data communication needs with the 2m DB9 female-to-female cable, an efficient solution designed to meet your serial connectivity requirements easily and efficiently.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Explorer 16/32 development board as your development board.
Track your results in real time
Application Output via Debug Mode
1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.
2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.
Software Support
Library Description
This library contains API for RS232 Click driver.
Key functions:
rs232_generic_write- Generic write function.rs232_generic_read- Generic read function.
Open Source
Code example
This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.
/*!
* \file
* \brief Rs232 Click example
*
* # Description
* This example reads and processes data from RS232 clicks.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes driver.
*
* ## Application Task
* Depending on the selected mode (receiver/transmitter) this function reads/sends an appropriate message.
* All data is displayed on USB UART.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "rs232.h"
#include "string.h"
#define PROCESS_RX_BUFFER_SIZE 500
#define RS232_TRANSMITTER
// #define RS232_RECEIVER
// ------------------------------------------------------------------ VARIABLES
static rs232_t rs232;
static log_t logger;
static int32_t rsp_size;
static char uart_rx_buffer[ PROCESS_RX_BUFFER_SIZE ] = { 0 };
static char message[ ] = "MikroE";
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
rs232_cfg_t cfg;
/**
* 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.
rs232_cfg_setup( &cfg );
RS232_MAP_MIKROBUS( cfg, MIKROBUS_1 );
rs232_init( &rs232, &cfg );
Delay_ms( 100 );
#ifdef RS232_RECEIVER
log_printf( &logger, " ** RS232 Receiver **\r\n" );
#endif
#ifdef RS232_TRANSMITTER
log_printf( &logger, " ** RS232 Transmitter **\r\n" );
#endif
}
void application_task ( void )
{
#ifdef RS232_RECEIVER
rsp_size = rs232_generic_read( &rs232, uart_rx_buffer, PROCESS_RX_BUFFER_SIZE );
if ( rsp_size == strlen( message ) )
{
log_printf( &logger, "Message received: %s", uart_rx_buffer );
log_printf( &logger, "\r\n-------------------------\r\n" );
memset( uart_rx_buffer, 0, rsp_size );
}
Delay_ms( 100 );
#endif
#ifdef RS232_TRANSMITTER
rs232_generic_write( &rs232, message, strlen( message ) );
log_printf( &logger, "Message sent: %s", message );
log_printf( &logger, "\r\n-------------------------\r\n" );
Delay_ms( 1000 );
#endif
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
