10 years, 7 months ago.

Problem to read from 2 RFID devices simultaneously

Hello,

I need to read RFID tags from 2 separate ID-12 reader. But this does not work when both rfid readers are connected !! No chars go out both ID-12 The code read well when only one rfid reader is connected (+5v disconnected on the other, not only Rx). One or the other work well, but not both simultaneously.

To do so, I connect 2 ID-12 respectively on rx pins 10 and 14. The code is : Print RFID tag numbers

include "mbed.h"
include "ID12RFID.h"
ID12RFID rfid1(p10); serial1 rx
ID12RFID rfid2(p14); serial2 rx

int main() {
printf("test twin simultaneous RFID ID-12 devices \n");

while(1) {
  if(rfid1.readable()) {
  printf("RFID Tag number : %d\n", rfid1.read());
  }
  if(rfid2.readable()) {
   printf("RFID Tag number : %d\n", rfid2.read());
  }
 }
}

I have suspected various hypothesis :

- not enough 5V supply (ID-12 require 30 mA, VU fall to 4,2V when both ID-12 are connected), but nothing better with and external power supply :-(

- devices may be too near from each other (RF could perturbate ?). Adding a long cable to have a 2 meter distance don't solve the problem :-((

- to see if there is RF influence, I tried 2 ID-12 but with 2 separate MBED : both work fine but separately :-(((

Anyone could suggest me what is wrong ?

Thanks in advance. Dominique