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.
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.
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.