Legal Removal Request

Post: Please ignore my previous post. I tried building the same setup as you are testing with an ESP32 module and two RS485 Pis and I had the same problem as you with the ESP32 receiving data from the Raspberry Pi but not transmitting data back to the Pi. [img]/docs/forumpost/clsya8h.jpg[/img] After testing all of the connections with a logic analyser I found the transmit line on the ESP32 module was not fully pulling the MOSFET Q1 low on the RS485 Pi when it transmitted so the RS485 Pi was staying in receive mode. The output on the logic analyser showed that Q1 did switch off at the end for a fraction of the transmission time so the Raspberry Pi saw some short random spikes which would explain the garbage on the Raspberry Pi end. One possible cause for this could be the TX pin on the ESP32 can not supply enough current to switch the MOSFET. To fix the problem I modified the RS485 Pi on the ESP32 end by moving the 0R resistor on R6 to the empty R7 pads which isolate the Q1 MOSFET from the transmit pin and connects it instead to GPIO17 (pin 11) on the GPIO header. I then connected pin 11 on the RS485 Pi to GPIO15 on the ESP32 module. This allows the ESP32 to control when the RS485 Pi is in transmit mode by pulling GPIO17 low and high. I modified the ESP32 code to control the GPIO pin manually before and after a serial write command. [pre][code]#include #include HardwareSerial ser(1); void setup(){ pinMode(15, OUTPUT); // Set GPIO15 as digital output pin. Connect to GPIO17 (pin 11) on RS485 Pi header. digitalWrite(15, HIGH); // Set GPIO15 high Serial.begin(115200); ser.begin(115200, SERIAL_8N1, 16, 17); } void loop(){ if(ser.available()){ String data = ser.readStringUntil('\n'); Serial.println(data); digitalWrite(15, LOW); // Set GPIO15 low ser.write("Hello from esp32\n"); ser.flush(); // wait for the write to complete digitalWrite(15, HIGH); // Set GPIO15 high delay(1000); } }[/code][/pre] After the ser.write command I added a ser.flush which makes the ESP32 wait for the transmit buffer to empty before setting GPIO15 high. I tested the modified setup at baud rates up to 115200 and it appears to be working correctly. Hopefully, you can use the same solution on your project.