ReadUidMultiReader is not working

[giddel]

I've tried the Ino with minimal changes (other pins).
As long as 2 readers are physically plugged, nothing works.
But if one reader is removed physically from the breadboard, the other works fine.
It does not matter, which reader is plugged. Both are working fine with this Ino if they are the only reader. All tags get regognized.
Nothing goes if both readers are wired. I've checked the wiring more than once. I have no more idea. Any hints?

[lmmeng]

@giddel: it is working for me quite well on more Arduino boards (Uno, Leonardo, Nano). Please post your changes (actually the full setup will be better). Please post the readers' versions also (read them after
mfrc522[reader].PCD_Init(ssPins[reader], RST_PIN); // Init each MFRC522 card
with a command like
byte readReg = mfrc522[reader].PCD_ReadRegister(mfrc522[reader].VersionReg);
and print them)

LE The library version will be also interesting.

[Rotzbua]

@giddel I suggest wrong pins for both SS

[giddel]

The pins are:
...
#define RST_PIN 10
#define SS_1_PIN 9
#define SS_2_PIN 8
...
on my Arduino Nano.

@lmmeng: which "library" do you mean? I use the lib here from this project.

I will rebuild the complete layout on the board and come back then.

[lmmeng]

I was meaning the library's version, but as long the sketch is compiling, I suppose is OK.
From the software point of view, it looks OK for me, but as @Rotzbua says, it looks like a SS problem. Please check the connections to don't have a short-circuit between the two SS.

[giddel]

So.
I'v rebuild the complete layout on my breadboard - without any changes of the pin layout against the example sketch here.
And I gave the two readers a separate power supply of 3,3V.

But: nothing changed. The one reader works, the other reader works, both together don't work.

I'm using the latest library version from the repo here: 1.1.8
The output of "VersionReg" is "0" for each reader.

[lmmeng]

Hello @giddel,
You say you have the layout on the breadboard. How long are the connecting wires?
Have you connected the grounds of the Arduino and MFRC522s together?
The version you are reading is also strange. Till now I've seen 0x11, 0x91, 0x92. Are you reading the version with only one reader connected, or with both of them?
Do you have any pull-ups/pull-downs on the wires? Something on MISO signal?
As a side note, I'm using without issues one Arduino (different types of) with two readers, all supplied from the USB port of my laptop.

[Rotzbua]

0 means there is a connection problem.
Try not connect the reset pins or connect them with the hardware reset pin of the arduino.

[dgriggs]

I'm having a similar issue as giddel. When I call the versions of 2 connected RFID readers, I get 146 (in hex: 0x92) for the zeroth reader, and 0 for other. When I hook up 6 readers, I get 146 again for the zeroth and 0s for all the rest. When I hook up 10 readers I get 0s on all of them. Occasionally one of them will read chip UIDs, but sporadically. Hooking one up alone works every time.

@lmmeng please describe the setup you used to comm with 2 boards. Does SPI not travel well across 1-2 ft of typical 18 gauge single-core wire? I'll have my oscilloscope tomorrow to check for signal issues. I'm daisy chaining everything except Slave Selects (which are all in separate Arduino Uno I/O pins 3-9 and 17-19). Yet somehow I'm not connecting to most of my boards.

@Rotzbua I tried leaving reset pins unconnected and also connecting to hardware reset, both resulted in all 0s for VersionReg's

[dgriggs]

Hmm just tried 6 readers again and got 146 for the first 4, 0s for the last 2. Not sure what's changing between these trials? I'll check for loose breadboard connections again... continuity test showed all wires successfully daisy chained, but maybe the readers are sensitive?

I tested all 10 readers one at a time with the example code DumpInfo. All cards read out 0x92 version 2.0 and successfully read the same chip with correct data output.

[Rotzbua]

May try:
julienrat@2e35032

[lmmeng]

Hello @dgriggs,
I've used the combination "one controller - two readers" in more combination (with arduino & ESP8266); all worked as expected.
I've done the first tests using a hand wired (holes) PCB; a picture before adding the second reader is at http://forum.rocrail.net/viewtopic.php?f=45&t=9965&start=105#p99580 . I've placed the second reader (a new male connector) on free side (right side in the picture) of the board. No special precaution by "routing" - some signals are carried from one connector to the other, some are in parallel.
One reader is connected directly (female connector on the MFRC522 board) and one with ~20 cm cable (no idea how thick).
Maybe you can test with some slower SPI clock. Because all SPI transactions are "resetting" the communication to the SPI_CLOCK_DIV4, I'll try to change the define for this (in the spi.h file) to a slower one.

I hope I could help a little.

[dgriggs]

@lmmeng no permission to view files at that forum. I tried making a login but for some reason the site will not accept my email address :/

This is all helping, thank you for the timely response!

@Rotzbua I believe a longer startup time is helping, but with all 10 it still fails (all 0's). I'll keep toying with it and see what I come up with.

[Rotzbua]

I agree with @lmmeng, the example works with arduino or esp8266 and two readers. Here a pic of esp:

10 readers is a lot.
Maybe you need a additional power source for the readers.
Or the amount of readers have a significant capacity, so it cause some timing delays of SPI. So as lmmeng wrote, lower SPI speed will be a solution.

[dgriggs]

Thanks! I figured the code wasn't meant for 10+ readers, no surprise there. I'm at a point where I'm at least getting non-zero VersionReg values from all 10 readers, but only the last one read 0x92, the others were one 0x82 and eight 0xEE's... not sure what to make of that. I'll try slowing down the SPI, although I'm not experienced in manipulating libraries (as you can see from my problems with yours hehe).

[dgriggs]

For now i'd like to at least get my Uno working with 2 of em... I have 0x92 from both readers, but one of them won't read my chips, only one.