5.1.2 I2C_Write Command and its Response

The I2C_Write command (0x44) initiates an I²C write transaction. The command writes wWrDtLen bytes of the data, vDatPac to the I²C client device addressed by bAddress.

This command is sent through Endpoint 0x03 (OUT). The response is read through Endpoint 0x83 (IN).

If the write data length exceeds the payload capacity of a single USB packet, multiple packets are used. The first packet contains up to 60 data bytes, and each additional continuation packets contains up to 62 data bytes.

A response is provided after the initial command packet, after each continuation packet, and after the write transaction completes or is aborted.

Table 5-4. `I2C_Write` - Command
Serial No.	Byte Index	Command		Description
1	0	`0x44`	Command code	Initiates the I²C write transaction
2	1	`bAddress`	I²C client address	7-bit I²C client address
3	2	`L(wWrDtLen)`	Write data length (lower byte)	Number of data bytes; maximum length: 65,535 bytes
4	3	`H(wWrDtLen)`	Write data length (upper byte)	Number of data bytes; maximum length: 65,535 bytes
5	4	`b0(vDatPac)`	First data byte	The first 60 data bytes
6	5	`b1(vDatPac)`	Second data byte
7-63	…	`…`	Additional data bytes
64	63	`b59(vDatPac)`	60^th data byte
65	Wait for the first response from the MCP2222 to determine whether the command is accepted. If the data length is more than 60 bytes, continue writing.
66	0	`0x44`	Repeat the command code	Write is continued
67	1	`0xA0`	Write is continued	Write is continued
68	2	`b60(vDatPac)`	The 61^st data byte	The next 62 data bytes
69-126	…	…	Additional data bytes
127	63	`b121(vDatPac)`	The 122^nd data byte
128	Wait for the next response
129	If all data bytes have not been written, continue writing by repeating the above steps from serial number 66 to 128 until all data bytes are written. The final packet may contain fewer than 62 data bytes.
130	Continue polling for the write-completion response

Table 5-5. `I2C_Write` - First Response
Byte Index	First Response		Description
0	`0x44`	Return command code	Returns whether the `I²C Write` command was accepted or rejected
1	`0x22`	Accepted - initiated	The command is accepted, and an I²C write transaction is initiated
	`0x60`	Rejected - wrong parameters	The command is rejected because the parameters are invalid
	`0x64`	Rejected - I²C is busy	The command is rejected because the I²C module is busy

Table 5-6. `I2C_Write` - Subsequent Response
Byte Index	Subsequent Responses		Description
0	`0x44`	Return command code	The I²C write is continued.
1	`0x22`	Accepted - write continued	The I²C write is continued.
	`0x68`	Rejected - buffer full	The Write buffer is full. Retry sending the same packet until it is accepted.
	`0x80`	Failure - address NACK	An address NACK was received. Verify the I²C client address.
	`0x84`	Failure - data NACK	A data NACK was received. Verify the client device requirements and the data length.
	`0x88`	Failure - clock-stretch timeout	A clock-stretch timeout occurred. Recover the bus and retry, if required.
	`0x8C`	Failure - arbitration lost	Bus arbitration was lost; another I²C host may be using the bus.
	`0x20`	Success – write completed	The `I2C_Write` transaction is completed.
	`0x90`	Failure - bus error	An I²C bus error occurred.