ESP8266 and RS485: Delay in transmission

Projects Programming
1

I'm using ESP8266 12E and the SN75176 chip RS485 for serial communication (see schematic) on the Arduino. In RS485 communication I use the digital output D8 from ESP8266 (GPIO15) as the data transmission control bit (high logic level in the transmission). Apparently works fine, but when I send data from ESP8266 to SN75176, I can only transmit all data if a delay of 1 millisecond is added after transmission and before I disable the "D8" control bit, as shown in example code. If I do the direct communication via RS232, that is, if I eliminate the chip SN75176 from the circuit, then the communication will no longer need delay. The amount of data I used in the test is only 10 bytes.

Is there a way to eliminate this delay using RS485 communication?

#define PIN_RS485    15
#define BUILTIN_LED  2

void setup() {
  pinMode(PIN_RS485, OUTPUT);
  pinMode(BUILTIN_LED, OUTPUT);
  
  Serial.begin(115200);
  
  digitalWrite(PIN_RS485, LOW);
}

void loop() {
   digitalWrite(PIN_RS485, HIGH);
   Serial.printf("0123456789");
   delay(1);
   digitalWrite(PIN_RS485, LOW);
   
   delay(50);
   digitalWrite(BUILTIN_LED, !digitalRead(BUILTIN_LED));
}

sch_inj2.jpg
sch_inj2.jpg3506×2478 427 KB

2

you mean direct TTL serial, not RS232? RS232 has logic 1 represented as negative voltage

3

tbh use 2 SN75176 chips, if you want both transmit and receive. the SN75176 is a transceiver, but switching between the modes takes a little time. wire one up as a receiver and the other as a transmitter. if you just want to transmit, don't switch it to receive mode all the time. or at least don't switch it to receive mode before it is done transmitting.

sch_inj2.jpg
sch_inj2.jpg3506×2478 427 KB

4

I am not convinced you understand the RS-485 protocol, understand that this is meant to counteract the effects of cable-capacitance on digital data transferthis
so 2 wires are used instead of one to transmit. and at the end not the actual voltgae but the difference in voltage between the 2 is measured using usually the same type of chip (there are multi-port variants available, and also just transmitters & receivers) check this and please do not cross-post.

5

I have already used the SN15176 chip with Atmega and PIC. I've never had this delay problem. I'm not understanding why it's needed as ESP8266.

Is there a way to eliminate this delay using RS485 communication + ESP8266?