Hi there,
And Welcome here…
SO you need to use the code tags when posting code “</>” paste it in there.
I gave it an edit. and It does compile. but it is missing some key parts?
You create two SOFTserials but never call them? and SoftwareSerial defaults to the last one that was started (or last one that called listen()), and the other will silently miss data.
Even worse: with two readers, you must explicitly switch which one is listening, e.g. poll like:
SoftSerial1.listen();
if (SoftSerial1.available()) ...
SoftSerial2.listen();
if (SoftSerial2.available()) ...
if you expect both to trigger independently, they won’t.
SoftwareSerial(rx, tx) means first pin is RX (Arduino receives on that pin).
RFID reader modules usually output serial data on their TX pin. That must go to Arduino RX.
So wiring must be:
- Reader TX → Arduino pin 2 (SoftSerial1 RX)
- Arduino pin 3 (SoftSerial1 TX) → Reader RX (often not even needed)
// RX/TX = D2 on base shield
this 
is nonsense. It’s not “RX/TX = D2”. It’s RX=D2, TX=D3.
On the Grove Base Shield for UNO-style boards, the UART socket is typically wired to D0/D1 (hardware serial), or there’s a switch/alternate port mapping depending on shield revision. If you are plugging the RFID reader into the shield’s UART port, but then using SoftwareSerial on D2/D3, your reading the wrong pins.
Verify the pins 
This is the classic failure mode: everything “runs” but available() never fires because the signal isn’t on those pins,
Some 125 kHz readers output:
Wiegand D0/D1 pulses, or TTL UART at 9600, or RS232-level output (needs level shifting)
If Your specific Grove readers are not the UART-output type, SoftwareSerial will never see bytes. The Seeed “Grove 125kHz RFID Reader” module does output UART, but clones/variants exist.
a minor bug i see in the logic ,
You clear the buffer by looping only to count, but resets count=0 after clearing anyway
– fine but pointless.
buffer is unsigned char “[.. ]” and You use NULL instead of 0.
No delay() in loop: not required, but it will spam and burn CPU.
– Add a delay (small one)
You never print the raw bytes nicely; many RFID readers send CR/LF and/or binary framing
– still, you should at least see something.
Use code Tags
// User posts 12/23/25 on SoftSerial.
// Xiaa Seeeduino..
#include <SoftwareSerial.h>
SoftwareSerial SoftSerial1(2,3); // RX/TX = D2 on base shield
SoftwareSerial SoftSerial2(5,6); // RX/TX = D5 on base shield
unsigned char buffer[64]; // buffer array for data receive over serial port
int count = 0; // counter for buffer array
int n = 0;
void setup()
{
SoftSerial1.begin(9600); // the SoftSerial baud rate
SoftSerial2.begin(9600); // the SoftSerial baud rate
Serial.begin(9600); // the Serial port of Arduino baud rate.
Serial.println("hello from seeeduino");
}
void loop()
{
// if data is coming from a software serial port ==> data is coming from SoftSerial shield
if (SoftSerial1.available())
{
Serial.println("data on SoftSerial1");
while(SoftSerial1.available()) // reading data into char array
{
buffer[count++] = SoftSerial1.read(); // writing data into array
if(count == 64)break;
}
Serial.write(buffer, count); // if no data transmission ends, write buffer to hardware serial port
clearBufferArray(); // call clearBufferArray function to clear the stored data from the array
count = 0; // set counter of while loop to zero
}
if (SoftSerial2.available())
{
Serial.println("data on SoftSerial2");
while(SoftSerial2.available()) // reading data into char array
{
buffer[count++] = SoftSerial2.read(); // writing data into array
if(count == 64)break;
}
Serial.write(buffer, count); // if no data transmission ends, write buffer to hardware serial port
clearBufferArray(); // call clearBufferArray function to clear the stored data from the array
count = 0; // set counter of while loop to zero
}
if (Serial.available()) // if data is available on hardware serial port ==> data is coming from PC or notebook
{
Serial.println("data received on serial port: ");
while(Serial.available()) // reading data into char array
{
buffer[count++] = Serial.read(); // writing data into array
if(count == 64)break;
}
//Serial.write(buffer, count); // if no data transmission ends, write buffer to hardware serial port
Serial.write(buffer, count);
Serial.print("\\nchars rcvd: ");
Serial.println(count);
clearBufferArray(); // call clearBufferArray function to clear the stored data from the array
count = 0; // set counter of while loop to zero
//SoftSerial.write(Serial.read()); // write it to the SoftSerial shield
}
n++;
}
void clearBufferArray() // function to clear buffer array
{
// clear all index of array with command NULL
for (int i=0; i<count; i++)
{
buffer[i]=NULL;
}
Serial.println("\\ncleared buffer");
}
I would have a Look at this posts, should see what you have missed..
The theory is the same, make sure the pins you use are capable and you initialize them properly first. Also , be sure you DON’T have 3.3v and 5V mixed together.
Try this;
Use only one SoftwareSerial and wire directly:
- Reader TX → Arduino D2
- Reader RX → Arduino D3 (optional; many readers don’t need it)
- GND ↔ GND, VCC ↔ 5V (or 3.3V if required)
Minimal sketch;
#include <SoftwareSerial.h>
SoftwareSerial rfid(2, 3); // RX, TX
void setup() {
Serial.begin(115200);
rfid.begin(9600);
rfid.listen();
Serial.println("Ready");
}
void loop() {
while (rfid.available()) {
int c = rfid.read();
Serial.write(c);
}
}
if you get that going , then add the Second one;
SoftSerial1.listen();
read_if_any(SoftSerial1);
SoftSerial2.listen();
read_if_any(SoftSerial2);
And accept you can’t truly read both simultaneously, the Kitchen sink approach almost 
Never works. You are using the Grove UART ports, so you must confirm: what pins do those sockets map to on that shield revision. If it’s D0/D1, you should use Serial (hardware UART) not SoftwareSerial.
HTH
GL 
PJ 
