getting E1 or E2 error

[zionnoizy]

whenever I screen the card, it only prints E1 or E2, but I have no idea where E1 or E2 comes from? I follow the instruction in here:

http://www.penguintutor.com/news/raspberrypi/rfid-rc522

how to avoid the errors to print "Detected" successfully?

#!/usr/bin/python3

import sys
sys.path.insert(0, "/home/pi/pi-rc522/ChipReader")
from pirc522 import RFID
import signal
import time
import RPi.GPIO as GPIO
from mfrc522 import SimpleMFRC522

reader = RFID()
util = reader.util()
util.debug = False

print("reader= ", reader)
print("util= ", util)

while True:
    (error, data) = reader.request()
    print("reader.request()= ", reader.request()) 
    if not error:
        print("\nDetected")
        (error, uid) = reader.anticoll()
        if not error:
            print ("str(uid[0]) " +str(uid[0])+ ", "+str(uid[1])+", "+str(uid[2])+", "+str(uid[3]))
            time.sleep(1)

print E1/E2 cannot print Detected, all connection and installation should work.

[nanbuwks]

In pirc522/rfid.py, lines 191 and 221, we have the corresponding code.

print("E1")

so we have
print("E1", file=sys.stderr)
should be

[Riccardo Tosi]

I have a similar problem, sometimes I read a tag and I get "E2" error, I tried to read the code but I have no Idea what the reason is.

Can someone help me please?

Thank you

[nanbuwks]

There are several ways to solve this, but if you do not want to rewrite lines 191 and 221 of the library, you can use
You can use redirect_stdout.
In Python 3.5 or later, this can be achieved as follows:

import io
import os
from contextlib import redirect_stdout

from pirc522 import RFID
rdr = RFID()

f = io.StringIO()

while True:
  rdr.wait_for_tag()
  with redirect_stdout(f):
      (error, tag_type) = rdr.request()
  # print(f.getvalue())  # if need print "E1" or "E2"
  if not error:
    print("Tag detected")
    with redirect_stdout(f):
      (error, uid) = rdr.anticoll()
    # print(f.getvalue())  # if need print "E1" or "E2"
    if not error:
       print("UID: " + str(uid))

# Calls GPIO cleanup
rdr.cleanup()

If you do not need to capture E1 and E2, you can use

f = open(os.devnull,'w')

instead of

f = io.StringIO()

.

[Riccardo Tosi]

Hi nanbuwks,
thank you for the answer, but I'm more interested in knowing why the error occours (and maybe solve or manage it) than suppress the message.

[nanbuwks]

Since we are using radio waves, there will always be errors at the boundary of the reaction.

However, aren't you plagued by a large number of errors?

When I used such a module as it is, it was quite unstable as shown below.

Detected
Card read UID: 242,195,43,51
Selecting UID [242, 195, 43, 51, 41].
Changing used auth key to [255, 255, 255, 255, 255, 255] using method B
Calling card_auth on UID [242, 195, 43, 51, 41].
E2
Error on S1.0B0
Not calling card_auth - already authed
S1.0B0: [2] B
Calling card_auth on UID [242, 195, 43, 51, 41].
Error on S1.0B2
Changing used auth key to [255, 255, 255, 255, 255, 255] using method A
Calling card_auth on UID [242, 195, 43, 51, 41].
Not calling card_auth - already authed
Not calling card_auth - already authed
S2.0B1: []
Calling card_auth on UID [242, 195, 43, 51, 41].
Error on S0.0B0
Calling card_auth on UID [242, 195, 43, 51, 41] Error on S0.0B0
Error on S0.0B1
Calling card_auth on UID [242, 195, 43, 51, 41] Error on S0.0B1
Error on S0.0B2
.
.
.
Calling card_auth on UID [242, 195, 43, 51, 41]
Error on S15.0B2
Calling card_auth on UID [242, 195, 43, 51, 41] Error on S15.0B2
Error on S15.0B3
Changing auth key and method to None

To solve this problem, adding a capacitor was effective.

In the picture, a 47μF capacitor has been installed to improve the 3.3V power supply.