RC522Hacking - Revision history

Bertrik Sikken at 13:17, 11 May 2020

2020-05-11T13:17:42Z

← Older revision		Revision as of 13:17, 11 May 2020
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	{{Project		{{Project
	\|Name=RC522Hacking		\|Name=RC522Hacking
	\|Status=~~In progress~~		\|Status=Completed
	\|Picture=rc522.jpg		\|Picture=rc522.jpg
	\|Contact=bertrik		\|Contact=bertrik

Bertrik Sikken at 16:41, 9 September 2018

2018-09-09T16:41:38Z

← Older revision		Revision as of 16:41, 9 September 2018
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	\|Name=RC522Hacking		\|Name=RC522Hacking
	\|Status=In progress		\|Status=In progress
			\|Picture=rc522.jpg
	\|Contact=bertrik		\|Contact=bertrik
	}}		}}

Bertrik Sikken: Clarification

2015-08-13T21:23:42Z

Clarification

← Older revision		Revision as of 21:23, 13 August 2015
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	This schematic only vaguely resembles the example circuit in the datasheet.		This schematic only vaguely resembles the example circuit in the datasheet.
	For example, I don't see any resistance in the resonance circuit to bring down the ~~Q (one of the datasheet recommends a Q of about 35)~~.		For example, I don't see any resistance in the resonance circuit to bring down the quality factor.

	=== Results ===		=== Results ===
	==== ~~Quick~~ fix ====		==== Resonance capacitance fix ====
	TDLR, my most up-to-date fix is:		TDLR, my most up-to-date fix is:
	* replace C8 and C9 with a 100 pF capacitor		* replace C8 and C9 with a 100 pF capacitor

	This enables reading of all cards I currently own, but seems to reduce the reading distance a bit for the card that came shipped with it.		This enables reading of all cards I currently own, but seems to reduce the reading distance a bit for the card that came shipped with it.
	I can't really justify the 100 pF value~~, it~~'s been empirically ~~determined~~ (~~try and see if~~ it ~~works~~)		I can't really justify the 100 pF value. It's been determined empirically. With this value, the resonant circuit sees about the same capacitance (200 pF) as it saw in the not-properly-soldered-but-working situation (220 pF), only now more symmetrical.

	==== ~~Not yet tried~~ fix ====		==== Damping resistor fix ====
	~~Another idea (to be~~ tested):		This has not been tested yet, only theoretically determined.
	~~Instead of replacing C8/C9 with a lower value,~~ replace C10/C11 with resistors, resulting in a _parallel_ damped resonant circuit. a The ~~resistors should be~~ chosen such the resonant circuit gets a Q of about 35.
	Given an L of 0.5 uH, a C of 220 pF and a desired Q of 35, the parallel resistance to be substituted in place of C10/C11 should be about 1700 ohm.		The fix is to replace C10/C11 with resistors, resulting in a _parallel_ damped resonant circuit.
			The theory is that we need some damping in the resonant circuit to widen its bandwidth. Probably C10/C11 don't actually do much (couldn't measure capacitance, so it's likely to be a rather small value compared to C8/C9, probably very much smaller than 100 pF), so we can safely replace these capacitors by resistors.
			The resistor value is chosen such the resonant circuit gets a Q of about 35, as recommended in the antenna design application note.

			Given an L of 0.5 uH (for one half of the reader/writer coil), a C of 220 pF (C8/C9) and a desired Q of 35, the parallel resistance to be substituted in place of C10/C11 should be about 1700 ohm.

	=== References ===		=== References ===

Bertrik Sikken: Update resistor fix

2015-08-12T16:01:30Z

Update resistor fix

← Older revision		Revision as of 16:01, 12 August 2015
Line 34:		Line 34:

	=== Results ===		=== Results ===
			==== Quick fix ====
	TDLR, my most up-to-date fix is:		TDLR, my most up-to-date fix is:
	* replace C8 and C9 with a 100 pF capacitor		* replace C8 and C9 with a 100 pF capacitor

	This enables reading of all cards I currently own, but seems to reduce the reading distance a bit for the card that came shipped with it.		This enables reading of all cards I currently own, but seems to reduce the reading distance a bit for the card that came shipped with it.
			I can't really justify the 100 pF value, it's been empirically determined (try and see if it works)

	~~Further ideas~~ (to be tested):		==== Not yet tried fix ====
	* Instead of replacing C8/C9 with a lower value, replace C10/C11 with resistors, resulting in a _parallel_ damped resonant circuit. a The resistors should be chosen such the resonant circuit gets a Q of about 35.		Another idea (to be tested):
			Instead of replacing C8/C9 with a lower value, replace C10/C11 with resistors, resulting in a _parallel_ damped resonant circuit. a The resistors should be chosen such the resonant circuit gets a Q of about 35.
			Given an L of 0.5 uH, a C of 220 pF and a desired Q of 35, the parallel resistance to be substituted in place of C10/C11 should be about 1700 ohm.

	=== References ===		=== References ===

Bertrik Sikken: Add future ideas

2015-08-12T14:35:35Z

Add future ideas

← Older revision		Revision as of 14:35, 12 August 2015
Line 38:		Line 38:

	This enables reading of all cards I currently own, but seems to reduce the reading distance a bit for the card that came shipped with it.		This enables reading of all cards I currently own, but seems to reduce the reading distance a bit for the card that came shipped with it.

			Further ideas (to be tested):
			* Instead of replacing C8/C9 with a lower value, replace C10/C11 with resistors, resulting in a _parallel_ damped resonant circuit. a The resistors should be chosen such the resonant circuit gets a Q of about 35.

	=== References ===		=== References ===

Bertrik Sikken at 12:13, 12 August 2015

2015-08-12T12:13:21Z

← Older revision		Revision as of 12:13, 12 August 2015
Line 26:		Line 26:

	The image on the right shows the reverse engineered part of the circuit that sits between the RC522 chip and the reader/writer coil.		The image on the right shows the reverse engineered part of the circuit that sits between the RC522 chip and the reader/writer coil.
	The reader/writer coil itself is about ~~40x30mm~~, with an estimated inductance of about 1 uH, it is center-tapped to the TVSS signal.		The reader/writer coil itself consists of 4 turns, each about 40x35 mm, with an estimated total inductance of about 1 uH, it is center-tapped to the TVSS signal.
			Assuming the total coil length is 54 cm, copper thickness is 35 um, trace width is 0.8 mm, the resistance can be calculated to be about 0.33 ohm.
	I was able to measure C8/C9 (220 pF), somehow I couldn't get a capacitance reading of circuit parts C6/C7/C10/C11.		I was able to measure C8/C9 (220 pF), somehow I couldn't get a capacitance reading of circuit parts C6/C7/C10/C11.

Bertrik Sikken: Add adafruit link

2015-08-12T11:58:17Z

Add adafruit link

← Older revision		Revision as of 11:58, 12 August 2015
Line 41:		Line 41:
	* NXP [http://www.nxp.com/documents/data_sheet/MFRC522.pdf MFRC522 datasheet]		* NXP [http://www.nxp.com/documents/data_sheet/MFRC522.pdf MFRC522 datasheet]
	* NXP application note [http://eng.utah.edu/~mlewis/ref/NFC/AN1445.pdf AN1445], Antenna design guide		* NXP application note [http://eng.utah.edu/~mlewis/ref/NFC/AN1445.pdf AN1445], Antenna design guide
			* A document describing changes made to improve the RFID circuit of an Adafruit PN532 board: [https://www.adafruit.com/datasheets/PN532_AntennaDesign_v1.0.pdf Changes PN532 Breakout board]

Bertrik Sikken at 11:42, 12 August 2015

2015-08-12T11:42:42Z

← Older revision		Revision as of 11:42, 12 August 2015
Line 24:		Line 24:

	With respect to hardware, I ordered two of these boards, and one of them came with a poorly soldered capacitor (C8). This one actually worked with a mifare light card! Properly soldering the capacitor made it no longer work. It also gave me a chance to measure the capacitor value, it has a value about 220 pF.		With respect to hardware, I ordered two of these boards, and one of them came with a poorly soldered capacitor (C8). This one actually worked with a mifare light card! Properly soldering the capacitor made it no longer work. It also gave me a chance to measure the capacitor value, it has a value about 220 pF.

			The image on the right shows the reverse engineered part of the circuit that sits between the RC522 chip and the reader/writer coil.
			The reader/writer coil itself is about 40x30mm, with an estimated inductance of about 1 uH, it is center-tapped to the TVSS signal.
			I was able to measure C8/C9 (220 pF), somehow I couldn't get a capacitance reading of circuit parts C6/C7/C10/C11.

			This schematic only vaguely resembles the example circuit in the datasheet.
			For example, I don't see any resistance in the resonance circuit to bring down the Q (one of the datasheet recommends a Q of about 35).

	=== Results ===		=== Results ===
Line 29:		Line 36:
	* replace C8 and C9 with a 100 pF capacitor		* replace C8 and C9 with a 100 pF capacitor

	This enables reading of all cards I currently own.		This enables reading of all cards I currently own, but seems to reduce the reading distance a bit for the card that came shipped with it.

	=== References ===		=== References ===
	* NXP [http://www.nxp.com/documents/data_sheet/MFRC522.pdf MFRC522 datasheet]		* NXP [http://www.nxp.com/documents/data_sheet/MFRC522.pdf MFRC522 datasheet]
	* NXP application note [http://eng.utah.edu/~mlewis/ref/NFC/AN1445.pdf AN1445], Antenna design guide		* NXP application note [http://eng.utah.edu/~mlewis/ref/NFC/AN1445.pdf AN1445], Antenna design guide

Bertrik Sikken: Add link to image

2015-08-12T11:34:23Z

Add link to image

← Older revision		Revision as of 11:34, 12 August 2015
Line 15:		Line 15:

	=== Investigation ===		=== Investigation ===
			[[File:RFID-RC522.png\|right\|schematic]]

	My two main suspicions why this board doesn't quite work, are:		My two main suspicions why this board doesn't quite work, are:
	* some software problem, quite a few things can be modified in software (conductance of the driving transistors, sensitivity settings)		* some software problem, quite a few things can be modified in software (conductance of the driving transistors, sensitivity settings)

Bertrik Sikken at 16:32, 11 August 2015

2015-08-11T16:32:10Z

← Older revision		Revision as of 16:32, 11 August 2015
Line 23:		Line 23:
	With respect to hardware, I ordered two of these boards, and one of them came with a poorly soldered capacitor (C8). This one actually worked with a mifare light card! Properly soldering the capacitor made it no longer work. It also gave me a chance to measure the capacitor value, it has a value about 220 pF.		With respect to hardware, I ordered two of these boards, and one of them came with a poorly soldered capacitor (C8). This one actually worked with a mifare light card! Properly soldering the capacitor made it no longer work. It also gave me a chance to measure the capacitor value, it has a value about 220 pF.

			=== Results ===
			TDLR, my most up-to-date fix is:
			* replace C8 and C9 with a 100 pF capacitor

			This enables reading of all cards I currently own.

	=== References ===		=== References ===
	* NXP [http://www.nxp.com/documents/data_sheet/MFRC522.pdf MFRC522 datasheet]		* NXP [http://www.nxp.com/documents/data_sheet/MFRC522.pdf MFRC522 datasheet]
	* NXP application note [http://eng.utah.edu/~mlewis/ref/NFC/AN1445.pdf AN1445], Antenna design guide		* NXP application note [http://eng.utah.edu/~mlewis/ref/NFC/AN1445.pdf AN1445], Antenna design guide