Bit-bang I2C Masters

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Beginning from the FW version 0.2.6 and library version 0.1.12.16, SUB-20 provides additional four independent I2C master channels on GPIO24..31 compatible with I2C specification 3.0.

Header Pin	GPIO	Alternative I2C Master Function
9	GPIO24	SCLx0
10	GPIO25	SDAx0
11	GPIO26	SCLx1
12	GPIO27	SDAx1
13	GPIO28	SCLx2
14	GPIO29	SDAx2
15	GPIO30	SCLx3
16	GPIO31	SDAx3

Each channel can operate in Fast Plus (1000KHz), Fast (400KHz) and Standard (100KHz) modes. In Fast and Standard modes I2C masters support clock stretching.

SDAx, SCLx Pull-ups

Considering the fact that bit-bang I2C channels share the GPIO pins with other SUB-20 modules, there are no internal (mounted on SUB-20 board) pull-ups on these channels. Pull-ups must be provided on target board.

Clock Stretching

In Fast and Standard modes bit-bang I2C masters support clock stretching. Clock stretching pauses a transaction by holding the SCL line LOW. The transaction cannot continue until the line is released HIGH again. Slaves can hold the SCL line LOW to force the

master into a wait state until the slave is ready.

Functions