RS485 Expansion Board for XIAO | Seeed Studio Wiki

[giscus[bot]]

RS485 Expansion Board for XIAO | Seeed Studio Wiki

XIAO Communcate with RS485 Expansion Board

https://wiki.seeedstudio.com/XIAO-RS485-Expansion-Board/

[NguyenVanDong94]

i can convert to rs422?

[nfs0619]

Thanks for reaching out! For assistance with converting to RS422, we recommend contacting our technical support team at [email protected]. They can provide detailed guidance and clarify any questions regarding your setup.

[hlima]

schematics? when we add a c6 or c3, which pins are connected o RS485?

[nfs0619]

For detailed schematics and pin connections when adding C6 or C3 to RS485, please contact our technical support team at [email protected]. They can provide accurate documentation and further assistance.

[hlima]

Does this board only works when connected to another xiao board? I tried with a device that uses rs485 and it did not work. I set it to input and connected AB pins to the AB pins on the device. I did not use the GROUND pin only AB pins. I am using a XIAO C6 and programmed the serial to use pins D4, D5

[Harrison-Xu]

Here is Harrison from Seeed Studio technical support team.

Sorry we cannot provide the schematic file of this product currently.

This product cannot work independently without a XIAO connected to it. It's right to use D4 and D5 pins, so please share with us your hardware connection photo and code then we can continue to help you with it.

[hlima]

I do have a xiao c6 connected. My problem was that I initially confgured D4 as RX. Once I corrected that and configured D5 as RX everything worked. Thank you.

[Elu43]

@Harrison-Xu @hlima why do you use D4 or D5 as RX ? Pinout shows D7 (GPIO 17) as RX for the C6 ?

[hlima]

can we power the xiao C6 connected to the board using the 12V input (do not use the C6 USBC) ? My RS485 device has a GND/12V output pins and I wanted to use those to power the whole board including XIAO C6 without having to use an additional USBC power.

[rickyrockets]

Where can I find the HardwareSerial library for this?

[HM-sur]

The HardwareSerial library is in the official esp32 onboard package

[Elu43]

Why is there :

  mySerial.begin(115200, SERIAL_8N1, 7, 6); // RX=D4(GPIO6), TX=D5(GPIO7)

When we can see on the pin diagram that TX=D6=GPIO21 and RX=D7=GPIO20 ?

[ReKST-117]

Hi, you are correct. From the pin out diagram of XIAO esp32c3. D6=TX=GPIO21; D7=RX=GPIO20. So the correct comment should be: mySerial.begin(115200, SERIAL_8N1, 7, 6); // RX=D7(GPIO20), TX=D6(GPIO21)

[Elu43]

Actually after spending 2 days on it I discovered that on this expansion board, it's using a TP8485E chip to convert the signal. The inputs of this chip are actually physically connected to D4 and D5 on the expansion board. But it's easy to make a mistake looking at the pinout diagram. So for the C3 it needs to be :

mySerial.begin(115200, SERIAL_8N1, 7, 6); // RX=D5(GPIO7), TX=D4(GPIO6)

And for C6 :

mySerial.begin(115200, SERIAL_8N1, 23, 22); // RX=D5(GPIO23), TX=D4(GPIO22)

[TPPS999]

Working example for esp32s3

// RS485 on UART1 - TESTED & WORKING!
HardwareSerial RS485(1);
#define RS485_RX 6 // GPIO6 - Working configuration!
#define RS485_TX 5 // GPIO5 - Working configuration!
#define RS485_DE_RE 3 // GPIO3 - DE/RE control

void setup() {
// Keep USB Serial for debugging
Serial.begin(115200);
delay(1000);

Serial.println("=== XIAO ESP32S3 RS485 Test ===");
Serial.println("USB Serial: Debug messages");
Serial.println("UART1: RS485 communication");

// Initialize RS485 on UART1
RS485.begin(9600, SERIAL_8N1, RS485_RX, RS485_TX);
pinMode(RS485_DE_RE, OUTPUT);
digitalWrite(RS485_DE_RE, LOW);  // Start in RX mode

Serial.println("RS485 initialized successfully!");

}

void loop() {
// Send RS485 message
digitalWrite(RS485_DE_RE, HIGH); // TX mode
RS485.println("Hello RS485!");
RS485.flush();
digitalWrite(RS485_DE_RE, LOW); // RX mode

// Check for response
if (RS485.available()) {
    String response = RS485.readString();
    Serial.println("RS485 Response: " + response);
}

delay(1000);

}