Ethernet to I2C Converter NCD5500 Ethernet Module extra data

Hi all,
I’m sending 3 bytes of data in a message from an ip client to the NCD5500 so that it can pass it on to a DAC over I2C. The NCD Config Tool shows that the I2C converter receives 9 bytes over Ethernet and sends 9 bytes over serial.
Why 9 bytes if I’m only sending 3? The NCD Config Tool does not show the actual contents of the message so I don’t know where the data is coming from.
The documentation I have found so far about the NCD5500 does not talk about any additional data.
Can you please help?

Thanks.

I apologize, I’m seeing 13 bytes in traffic, not 9.

Hi,

If you’re sending 3 bytes over TCP and the NCD5500 is outputting 9 bytes through it’s UART it could be an issue of baud rate which can look like garbled bytes.

If you’re using something like Base Station or AnyI2C to communicate to the device those software will automatically wrap the 3 byte command into an API for the converter to be able to transform the serial/tcp data into i2c.

The API looks like this in decimal representation of bytes:

170: NCD API Header Byte
7: NCD API Data Indicates 7 Bytes will be sent in the API frame.
188: I2C Command Header (Always use 188 when talking to I2C Devices)
50: Port Number.  50 Indicates Port 0, 51 = Port 1, etc.  This adapter has only one I2C port, so always use 50.
3: Number of Bytes to Send to the I2C Chip
130: I2C Data to Configure I/O Lines as Output (See Datasheet for the PCA9536, as this is a chip command)
3: I2C Data to Configure I/O Lines as Output (See Datasheet for the PCA9536, as this is a chip command)
0: I2C Data to Configure I/O Lines as Output (See Datasheet for the PCA9536, as this is a chip command)
0: Number of Bytes to Read from the I2C Chip (Use 0 for this chip since we don’t need to read any data from the I2C chip)
39: Checksum