# I2c Wiring Harness?

**URL:** <https://discourse.securinghardware.com/t/i2c-wiring-harness/60>\
**Category:** APA#2: Hardware Pentesting\
**Created:** [December 13, 2021, 8:05am UTC](https://discourse.securinghardware.com/t/i2c-wiring-harness/60 "2021-12-13T08:05:08Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![AndrewMohawk](https://discourse.securinghardware.com/letter_avatar_proxy/v4/letter/a/3ab097/32.png) [@AndrewMohawk](https://discourse.securinghardware.com/u/AndrewMohawk)\
**Post date:** [December 13, 2021, 8:05am UTC](https://discourse.securinghardware.com/t/i2c-wiring-harness/60/1 "2021-12-13T08:05:09Z")

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I’d like to know where one can purchase the i2c harness, I dont have one included with my tigard and i’d like to look at an EEPROM that is embedded on a device but connecting by hand to those pins is gonna make me sad, can anyone suggest where I can get one?

Cheers!  
Andrew

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**Author:** ![joefitz](https://discourse.securinghardware.com/letter_avatar_proxy/v4/letter/j/838e76/32.png) [@joefitz](https://discourse.securinghardware.com/u/joefitz)\
**Post date:** [December 16, 2021, 6:41pm UTC](https://discourse.securinghardware.com/t/i2c-wiring-harness/60/2 "2021-12-16T18:41:02Z")

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There’s a few choices for I2c. Photos in this twitter thread: [https://twitter.com/securelyfitz/status/1461388618346291203](https://twitter.com/securelyfitz/status/1461388618346291203)

First, make sure the JTAG-SPI/I2C-SWD switch is in the I2C-SWD mode. That connects an input and output together to make a bidirectional SDA

1. You can use the JTAG harness on the jtag header to directly connect to devices that have .1" headers
2. You can use the SPI connector with a SOIC-8 clip, and the wires should be pinned correctly to clip right on to most SOIC-8 I2C EEPROMS as well as many other I2C devices that follow the same convention and put the i2c lines on pins 5&6
3. You can use the I2C header with STEMMA-QT or QWIIC devices and harnesses from adafruit, sparkfun, and others: [What is STEMMA QT? | Adafruit STEMMA & STEMMA QT | Adafruit Learning System](https://learn.adafruit.com/introducing-adafruit-stemma-qt/what-is-stemma-qt)

For making your own devices, you can find cheaper sources for “JST SH 1.0-4 Pin Connectors”. The SH 1.0 indicates it’s 1mm pitch compact connectors, not the more common JST 1.27, 2, and 2.54 mm pitch connectors. I have a bunch of premade pigtails from aliexpress, they’re also available cheap on ebay and amazon. Even the ones from sparkfun/adafruit are cheaper than the parts to make them yourself.

> **[Amazon.com: 20 Sets Mini Micro Sh 1.0 Jst 4-Pin Connector Plug Male with 150mm...](https://www.amazon.com/daier-Micro-4-Pin-Connector-Female/dp/B01DUC1M2O)**
>
> Condition: Brand NEW! JST SH 1.0-4 Pin Male Connector Plug with 15cm Wire x 20 pcs JST SH 1.0-4 Pin Female Connector x 20 pcs Cable Length : 150mm AWG:26AW

-joe

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**Author:** ![AndrewMohawk](https://discourse.securinghardware.com/letter_avatar_proxy/v4/letter/a/3ab097/32.png) [@AndrewMohawk](https://discourse.securinghardware.com/u/AndrewMohawk)\
**Post date:** [December 16, 2021, 8:31pm UTC](https://discourse.securinghardware.com/t/i2c-wiring-harness/60/3 "2021-12-16T20:31:54Z")

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Thanks Joe, thats exactly what I am looking for!