Huzzah Feather ESP8266 with MAX3232 as RS232 to wifi device

1/*
2 * Use an ESP8266 Huzzah Feather and MAX3232 board from MikroE to  communicate with an RS232 device 
3 * (a Dylos DC1700 particulates monitor here,  but could be anything) 
4 * 
5 * This board has only one UART; Pins labelled  Rx and Tx are shared with the USB port, so we have to use SoftwareSerial.
6 *  We choose pins 4 and 5 because they are the only two available that have no standard  use for other things.
7 * (ESP32 has 3 separate UARTs and would have been easier).
8  * The MAX3232 should be soldered to +3 V, GND and pins 4 and 5 (opposite corner  to the power pins). 
9 * I checked extensively: what the MAX3232 calls Rx is the  channel that *transmits* to the remote device; 
10 * what it labels as Tx is the  channel that receives from the other device. In other words, they are named
11  * as labelled on the other device. A null modem cable is needed from MAX3232 to  Dylos (with Rx and Tx crossed).
12 * You connect Huzzah Feather Tx = pin 4 to Tx  on the MAX3232; Huzzah Feather Rx = pin 5 to Rx on the MAX3232.
13 */
14#include  <SoftwareSerial.h>
15const byte txPin = 4;
16const byte rxPin = 5;
17SoftwareSerial  max3232(rxPin, txPin);
18  
19void setup() {
20
21  Serial.begin(9600L);
22
23  pinMode(txPin, OUTPUT);
24  pinMode(rxPin, INPUT);
25
26  max3232.begin(9600);
27  
28  while (!max3232.isListening()) {
29    Serial.println("Waiting for MAX3232  to start listening...");
30    delay(1000);
31  }
32  Serial.println("Good,  MAX3232 is listening");
33
34}
35
36
37void loop() {
38
39  Serial.println("Waiting  for data on Dylos");
40
41  for (int loops = 0; loops < 120; ++loops) {
42    if  (max3232.available()) break;
43    delay(1000);
44  }
45
46  char result[100]  = "-1, -1";
47  if (max3232.available()) {
48    Serial.println("reading Max3232...");
49    int i = 0;
50    while (max3232.available()) {
51      result[i++] = max3232.read();
52    }
53    result[i] = '\n'; // Just to check it is terminated
54  }
55  else  {
56    Serial.println("Timed out");
57  }
58  
59  Serial.println(result);
60  
61}
62

1/*
2 * Use an ESP8266 Huzzah Feather and MAX3232 board from MikroE to   communicate with an RS232 device 
3 * (a Dylos DC1700 particulates monitor here,   but could be anything) 
4 * 
5 * This board has only one UART; Pins labelled   Rx and Tx are shared with the USB port, so we have to use SoftwareSerial.
6 *   We choose pins 4 and 5 because they are the only two available that have no standard   use for other things.
7 * (ESP32 has 3 separate UARTs and would have been easier).
8   * The MAX3232 should be soldered to +3 V, GND and pins 4 and 5 (opposite corner   to the power pins). 
9 * I checked extensively: what the MAX3232 calls Rx is the   channel that *transmits* to the remote device; 
10 * what it labels as Tx is the   channel that receives from the other device. In other words, they are named
11   * as labelled on the other device. A null modem cable is needed from MAX3232 to   Dylos (with Rx and Tx crossed).
12 * You connect Huzzah Feather Tx = pin 4 to Tx   on the MAX3232; Huzzah Feather Rx = pin 5 to Rx on the MAX3232.
13 */
14#include   <SoftwareSerial.h>
15const byte txPin = 4;
16const byte rxPin = 5;
17SoftwareSerial   max3232(rxPin, txPin);
18  
19void setup() {
20
21  Serial.begin(9600L);
22
23   pinMode(txPin, OUTPUT);
24  pinMode(rxPin, INPUT);
25
26  max3232.begin(9600);
27   
28  while (!max3232.isListening()) {
29    Serial.println("Waiting for MAX3232   to start listening...");
30    delay(1000);
31  }
32  Serial.println("Good,   MAX3232 is listening");
33
34}
35
36
37void loop() {
38
39  Serial.println("Waiting   for data on Dylos");
40
41  for (int loops = 0; loops < 120; ++loops) {
42    if   (max3232.available()) break;
43    delay(1000);
44  }
45
46  char result[100]   = "-1, -1";
47  if (max3232.available()) {
48    Serial.println("reading Max3232...");
49     int i = 0;
50    while (max3232.available()) {
51      result[i++] = max3232.read();
52     }
53    result[i] = '\
54'; // Just to check it is terminated
55  }
56  else   {
57    Serial.println("Timed out");
58  }
59  
60  Serial.println(result);
61   
62}
63