About the article

The Secrets of I2C

An I2C bus analyser to let you satisfy your curiosity

The Secrets of I2C
This analysed can be used to troubleshoot a reluctant proprietary application or to ‘reverse engineer’ existing applications. The device communicates with a PC via a USB link configured as a virtual port (COMx) and so is powered directlyfrom the USB, avoiding the need for an external mains adaptor (or even batteries).
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list


R1,R2 = 8kΩ2

R3,R4 = 1MΩ5

R5,R6 = 330

R7,R13 = 470

R8 = 4kΩ7

R9,R10 = 10k

R11,R12 = 1k

R14,R15 = 27

R16 = 1kΩ5


C1,C2 = 1nF

C3,C4,C10 = 100nF

C5-C8 = 22pF

C9 = 10nF

C11,C12 = 33nF


D1 = LED, 3mm, red

D2 = LED, 3 mm, green

T1,T2 = 2N7000

IC1,IC2 = 4538

IC3 = PIC18F4520, programmed, Elektor shop item # 070600-41

IC4 = FT232BM (FTDI)


K1 = 6-way RJ-11 socket (vertical)

K3,K4,K5 = 6-way RJ-11 socket (horizontal)

K2 = USB socket, male, type B

L1 = ferrite bead

X1 = 20MHz quartz crystal, HC 49/4H case

X2 = 6 MHz quartz crystal, HC 49/4H case

S1 = miniature pushbutton

S2,S3 = ‘D6’ pushbutton (red and black)

JP1 = 3-way SIL pinheader with jumper

PCB, item # 070600-1

PCB artwork, free download from www.elektor.com

Project software (PC executable and .hex file), item # 070600-11
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