GATEWAY RS232, CAN, RS485 TO ETHERNET MQTT AT ATMEGA328
The brain is the Atmega328P microcontroller with a wired Arduino bootloader. For Ethernet communication, I chose a new W5500 chip from the manufacturer WIZnet Co., Ltd.
The W5500 chip — an addition to the line of popular WIZNet Ethernet chips — is a functionally complete embedded Ethernet controller chip for providing a wired TCP / IP connection, which simplifies the Internet connection of devices and systems using SPI (high-speed serial peripheral interface). The W5500 can meet the needs of users in a stable connection to the Internet, using a single chip to implement the TCP / IP stack, 10/100, Ethernet MAC and PHY. The TCP / IP hardware stack supports TCP, UDP, IPv4, ICMP, ARP, IGMP, PPPoE …
The role of the converter RS232-UART uses the chip MAX3232. Additionally, I made the board more versatile in terms of protocols. It is possible to install the TJA1040 chip and get a bus instead of the RS232, CAN bus. You can install the MAX485 chip and thus get RS485. However, simultaneous use is not provided and the choice of the protocol depends on the installed microcircuit of the converter.
The board is powered by a DC-DC converter built on the MC34063 chip, which has a wide input voltage range of 5.5 to 40 volts.
For management, I usually use the MQTT protocol. You can also fill in this sketch and we will get a fully-fledged configurable gateway. Connected by telnet to the gateway on port 24: telnet <ip-address> 24
we can change the following settings:
? — get <label>, <baudrate>, <parity>, <wordlength>, <stopbits>
Label [string] — get or set a custom label (up to 32 characters)
Baudrate [value] — get or set the transmission speed (300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200)
Parity [value] — get or set parity (N, E, O)
Wordlength [value] — get or set wordlength (5, 6, 7, 8)
Stopbits [value] — get or set stop bits (1, 2)
Save — saves the current settings in the EEPROM memory
Load — loads settings from EEPROM memory
Gerber files https://drive.google.com/file/d/1iPZrDc-d-xpWLXeyzlUTMXdm_ZsrgnGP/view?usp=sharing
Here is code:
// to store settings in memory
#include <EEPROM.h>
#include <SPI.h>
/*
* Uncomment one of the following lines depending on
* what ethernet library works with your board.
* If it is based on W5500 chip you will need
* Ethernet2.h and EthernetUdp2.h
*/
//#include <Ethernet.h>
//#include <EthernetUdp.h>
#include <Ethernet2.h>
#include <EthernetUdp2.h>
/*
* Enables debug mode and duplicates everything to USB Serial port
* Also prints ip address to the USB Serial port
* when recieves any characted to the USB Serial port
*/
#define DEBUG
// Port to send commands
#define CMD_PORT 23
// Port for configuration
#define CONTROL_PORT 24
// UDP port
#define UDP_PORT 8788
// label buffer size
#define LBLSIZE 64
// replace this with your mac address
byte mac[] = {
0x90, 0xA2, 0xDA, 0x10, 0x5C, 0xEE
};
/*
For manual configuration of the network uncomment the following lines
and change the Ethernet.begin arguments in the setup() function
*/
//IPAddress ip(192, 168, 1, 177);
//IPAddress gateway(192, 168, 1, 1);
//IPAddress subnet(255, 255, 0, 0);
/*
* ==================================
* Everything below should just work
* ==================================
*/
// structure to store settings of the serial port
struct ComSettings{
char label[LBLSIZE];
long baudrate;
char parity;
long wordlength;
long stopbits;
};
ComSettings settings;
// default serial port configuration
ComSettings defaults = {«Undefined», 9600, ‘N’, 8, 1};
long serialSettings(struct ComSettings s){
// this function returns serial configuration for Serial1 library
long conf = 0;
long wl = 3;
if(s.wordlength >= 5 && s.wordlength <= 8){
wl = s.wordlength-5;
}
long stp = 0;
if(s.stopbits==1 || s.stopbits==2){
stp = s.stopbits-1;
}
long p = 0;
if(s.parity==’E’){
p=2;
}
if(s.parity==’O’){
p=3;
}
conf = (p << 4) | (stp << 3) | (wl << 1);
return conf;
}
bool alreadyConnected = false;
bool controlAlreadyConnected = false;
EthernetServer cmdServer(CMD_PORT);
EthernetServer controlServer(CONTROL_PORT);
EthernetUDP Udp;
String cmd = «»;
//
void parseCmd(String s, EthernetClient client){
#ifdef DEBUG
Serial.println(«Recieved control command: «);
Serial.println(s);
#endif
if(s==»help»){
client.println(«Available commands:»);
client.println(«? — get <label>,<baudrate>,<parity>,<wordlength>,<stopbits>»);
client.println(«label [string] — get or set custom label for this box (up to 32 characters)»);
client.print(«baudrate [value] — get or set baudrate «);
client.println(«(300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200)»);
client.println(«parity [value] — get or set parity (N, E, O)»);
client.println(«wordlength [value] — get or set wordlength (5, 6, 7, 8)»);
client.println(«stopbits [value] — get or set stopbits (1, 2)»);
client.println(«save — saves current settings to EEPROM memory»);
client.println(«load — loads settings from EEPROM memory»);
}
bool changed = false;
if(s==»save»){
EEPROM.put(0, settings);
client.println(«Saved!»);
}
if(s==»load»){
EEPROM.get(0, settings);
client.println(«Loaded!»);
changed = true;
}
if(s==»?»){
client.print(settings.label);
client.print(«,»);
client.print(settings.baudrate);
client.print(«,»);
client.print(settings.parity);
client.print(«,»);
client.print(settings.wordlength);
client.print(«,»);
client.println(settings.stopbits);
}
int l = s.length();
if(s.startsWith(«label»)){
if(l>6){
s.substring(6).toCharArray(settings.label, LBLSIZE);
changed = true;
}
client.println(settings.label);
}
if(s.startsWith(«baudrate»)){
if(l>9){
settings.baudrate=s.substring(9).toInt();
changed = true;
}
client.println(settings.baudrate);
}
if(s.startsWith(«parity»)){
if(l>7){
settings.parity=s.charAt(7);
changed = true;
}
client.println(settings.parity);
}
if(s.startsWith(«wordlength»)){
if(l>11){
settings.wordlength=s.substring(11).toInt();
changed = true;
}
client.println(settings.wordlength);
}
if(s.startsWith(«stopbits»)){
if(l>9){
settings.stopbits=s.substring(9).toInt();
changed = true;
}
client.println(settings.stopbits);
}
if(changed){
reopenSerial();
}
}
void reopenSerial(){
Serial1.begin(settings.baudrate, serialSettings(settings));
#ifdef DEBUG
printConfig();
#endif
controlServer.println(«Settings changed:»);
controlServer.print(settings.label);
controlServer.print(«,»);
controlServer.print(settings.baudrate);
controlServer.print(«,»);
controlServer.print(settings.parity);
controlServer.print(«,»);
controlServer.print(settings.wordlength);
controlServer.print(«,»);
controlServer.println(settings.stopbits);
}
void checkControl(){
EthernetClient client = controlServer.available();
if (client) {
if (!controlAlreadyConnected) {
// clean out the input buffer:
client.flush();
controlAlreadyConnected = true;
}
if (client.available() > 0){
char c = client.read();
if(c==’\n’){
parseCmd(cmd, client);
cmd = «»;
}else{
if(c!=’\r’){ // ignoring \r
cmd += c;
}
}
}
}
}
void printConfig(){
Serial.print(«IP-address: «);
Serial.println(Ethernet.localIP());
if(!Serial1){
Serial.println(«Serial port is closed»);
}else{
Serial.println(«Serial port is opened»);
}
Serial.println(«Serial configuration:»);
Serial.print(«Label: «);
Serial.println(settings.label);
Serial.print(«Baudrate: «);
Serial.println(settings.baudrate);
Serial.print(«Parity: «);
Serial.println(settings.parity);
Serial.print(«Wordlength: «);
Serial.println(settings.wordlength);
Serial.print(«Stopbits: «);
Serial.println(settings.stopbits);
}
// buffers for receiving and sending data
char packetBuffer[UDP_TX_PACKET_MAX_SIZE]; //buffer to hold incoming packet,
char ReplyBuffer[] = «Serial gate v1.1»; // a string to send back
void checkUDP(){
// if there’s data available, read a packet
int packetSize = Udp.parsePacket();
if (packetSize)
{
#ifdef DEBUG
Serial.print(«Received packet of size «);
Serial.println(packetSize);
Serial.print(«From «);
IPAddress remote = Udp.remoteIP();
for (int i = 0; i < 4; i++)
{
Serial.print(remote[i], DEC);
if (i < 3)
{
Serial.print(«.»);
}
}
Serial.print(«, port «);
Serial.println(Udp.remotePort());
#endif
// read the packet into packetBufffer
Udp.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
packetBuffer[packetSize] = ‘\0’;
#ifdef DEBUG
Serial.println(«Contents:»);
Serial.println(packetBuffer);
#endif
if(strcmp(packetBuffer,»?») == 0){
// send a reply, to the IP address and port that sent us the packet we received
Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());
Udp.write(ReplyBuffer);
Udp.endPacket();
}
}
}
void setup() {
// For DHCP use only mac. For manual configuration use all parameters.
Ethernet.begin(mac);
// Ethernet.begin(mac, ip, gateway, subnet);
EEPROM.get(0, settings);
// very stupid check
if(settings.baudrate<300){
EEPROM.put(0, defaults);
EEPROM.get(0, settings);
}
cmdServer.begin();
controlServer.begin();
Udp.begin(UDP_PORT);
Serial1.begin(settings.baudrate, serialSettings(settings));
#ifdef DEBUG
Serial.begin(9600);
printConfig();
#endif
}
void loop() {
// wait for a new client:
EthernetClient client = cmdServer.available();
// to disable telnet control just comment the line below
checkControl();
checkUDP();
char c;
// transfer all bytes from client to Serial1
if (client) {
if (!alreadyConnected) {
// clean out the input buffer:
client.flush();
alreadyConnected = true;
}
if (client.available() > 0){
c = client.read();
Serial1.write(c);
#ifdef DEBUG
Serial.write(c);
#endif
}
}
// transfer all bytes to the cmdServer
// (all connected clients will recieve it)
if(Serial1.available() > 0){
c = Serial1.read();
cmdServer.write(c);
#ifdef DEBUG
Serial.write(c);
#endif
}
#ifdef DEBUG
if(Serial.available() > 0){
Serial.read();
printConfig();
}
#endif
}
Embedded world 