Не совем Вас понял. Смотрите, условно говоря:
Syntax
CAN.sendMsgBuf(id, ext, len, buf)
Parameters
id:Device ID for the remote CAN device
ext:Data transmission format
CAN_STDID:Standard data frame, comply with CAN 2.0A standard. ID range: 0 ~ 0x7FF
CAN_EXTID:Extended data frame, based on CAN...