5.1.7 I²C Communication Procedure

This section describes the typical command sequence for using the MCP2222 for I²C communication.

Writing to an I²C client device from a specified location:

Configure I²C:

Send the I2C_Config command through Endpoint 0x03 (OUT) with the following parameters:


Parameter	Value	Description
Command	`0x40`	Configure I²C
Clock speed	`0x70` `0x16` `0x04`	100 kHz clock speed. 400 kHz clock speed. 1 MHz clock speed.
Clock stretch timeout	`0x01` - `0xFA`	Clock-stretch timeout in milliseconds (8-bit hexadecimal)

Read the response through Endpoint 0x83 (IN). The responses can be one of the following:


Response code	Status	Action
`0x40`	Response to I²C Config	Continue reading
`0x20` `0x60` `0x64`	I²C is configured. Invalid parameters. I²C module busy.	Proceed with the write transaction. Retry with valid parameters. Wait and retry later.

Write transaction

Send the I2C_Write command through Endpoint 0x03 (OUT) with the following parameters:


Parameter	Value	Description
Command	`0x44`	Write to the I²C client device
I²C Client address	`bAddress`	7-bit I²C client address
Write data length	`wWrDtLen`	Number of bytes to be written including the location address, encoded as a 16-bit hexadecimal value
Location address	`vLocAdd`	Starting location from where the data should be written
Data bytes	`vDatPac`	Data to be written (up to 60 bytes, including the location address)

Read the initial response from Endpoint 0x83 (IN). Possible initial responses are:


Response code	Status	Action
`0x44`	Response to I²C Write	Continue reading
`0x22` `0x60` `0x64`	The I²C write transaction is initiated. Invalid parameters. The I²C module is busy.	Proceed to continue the write transaction. Retry with valid parameters. Wait and retry later.

If the number of data bytes to write exceeds 60 bytes, send continuation packets through Endpoint 0x03 (OUT). Each continuation packet includes:
Parameter Value Description
Command 0x44 Continue writing to the I²C client device
Continuation flag 0xA0
Data bytes vDatPac Data to be written (up to 62 bytes)

Parameter	Value	Description
Command	`0x44`	Continue writing to the I²C client device
Continuation flag	`0xA0`
Data bytes	`vDatPac`	Data to be written (up to 62 bytes)

After each continuation packet, and after the write transaction is completed, read the response from Endpoint 0x83 (IN). The response can be one of the following:


Response code	Status	Action
`0x44` `NACK`	Response to I²C Write. No response available yet.	Continue reading. Continue polling.
`0x22` `0x68` `0x80` `0x84` `0x88` `0x8C` `0x20`	The I²C write transaction is continued. The buffer is full. An address NACK occurred. A data NACK occurred. A clock-stretch timeout occurred. I²C bus arbitration was lost. The I²C write transaction is successfully completed.	Proceed to continue the write transaction. Retry until the packet is accepted. Retry with a valid address. Use a smaller data packet. Run bus recovery. Wait and retry (I²C bus in use).

Repeat sending continuation packet through Endpoint 0x03 (OUT) and polling Endpoint 0x83 (IN) until all required data bytes are written.

Reading data from an I²C client device from a specified location:

Configure I²C:
- Refer to the Configure I²C section of Writing to a I²C client device from a specified location.

Read data from specific locations of an I²C client device:

Send the I2C_WriteRead command through Endpoint 0x03 (OUT) with the following parameters.


Parameter	Value	Description
Command	`0x4A`	Write to and read from an I²C client device
I²C Client address	`bAddress`	7-bit I²C client address
Write data length	`wWrDtLen`	Number of bytes in the location address, encoded as a 16-bit hexadecimal value
Read data length	`wRdDtLen`	Number of bytes to be read, encoded as a 16-bit hexadecimal value
Location address	`vLocAdd`	Starting location from where the data should be read

Read the initial response from Endpoint 0x83 (IN). Possible initial responses are:


Response code	Status	Action
`0x4A`	Response to I²C WriteRead	Continue reading
`0x22` `0x60` `0x64`	I²C write-read transaction is initiated. Invalid parameters The I²C module is busy.	Proceed to continue polling for the next response. Retry with valid parameters. Wait and retry later.

Keep polling Endpoint 0x83 (IN) until read data is returned. Possible poll results:


Response code	Status	Action
`0x4A` `NACK`	Response to I²C WriteRead. No response available yet.	Continue reading. Continue polling.
`0x21` `0x84` `0x88` `0x8C`	The I²C write-read transaction continued. A data NACK occurred. A clock-stretch timeout occurred. I²C bus arbitration was lost.	Continue reading until the entire packet is read, then proceed to poll for the next response. Retry with the correct location address. Run bus recovery. Wait and retry (I²C bus in use).
`wRdDtLen`	The first 60 bytes of data are read	Continue reading
`vDatPac`		Read all the available data bytes from the endpoint. Continue reading until all packets have been read.

Repeat polling Endpoint 0x83 (IN), until all required data bytes are read:


Response code	Status	Action
`0x4A` `NACK`	Response to I²C WriteRead. No response available yet.	Continue reading. Continue polling.
`0x21` `0x88` `0x8C`	The I²C write-read transaction continued. A clock-stretch timeout occurred. I²C bus arbitration was lost.	Continue reading until the entire packet is read, then proceed to poll for the next response. Run bus recovery. Wait and retry (I²C bus in use).
`vDatPac`	The next 62 bytes of data are read.	Read all available data bytes from the endpoint. Continue reading until all packets have been read.

Recovering the I²C Bus on a Clock-Stretch Timeout

Send the I2C_BusRecovery command through Endpoint 0x03 (OUT) if a clock-stretch timeout occurs during a write, read, or writ-read transaction.


Parameter	Value	Description
Command	`0x4E`	Recover the I²C bus

Read the response from Endpoint 0x83 (IN).


Response code	Status	Action
`0x4E`	Response to I²C bus recovery	Continue reading
`0x20` `0x60` `0x80`	The I²C bus is recovered. No clock-stretch timeout was detected. Bus recovery failed.	The I²C bus is in the idle state. The bus is available for transaction. Retry by sending the command again.

Reading the logic states of the SCL and SDA lines:

To check the states of the SCL and SDA lines, follow these steps:

Send the I2C_GetSCLSDAStatus (0x4C) through Endpoint 0x03 (OUT).
Parameter Value Description
Command 0x4C Recover the I²C bus

Parameter	Value	Description
Command	`0x4C`	Recover the I²C bus

Read the response from Endpoint 0x83(IN).


Response code	Status	Action
`0x4C`	Response to I²C bus recovery	Continue reading
`0x21`	SCL and SDA states are read	Continue reading
`0x00` `0x00` `0x00` `0x00`	The SCL is in a low state, and the SDA is also in a low state The SCL is in a high state, and the SDA is in a low state The SCL is in a low state, and the SDA is in a high state The SCL is in a high state, and the SDA is also in a high state	Take the necessary action depending on the logical state read

5.1.7 I2C Communication Procedure

5.1.7 I²C Communication Procedure