HydraFW Binary CAN mode guide

#HydraFW binary CAN mode guide

This guide is updated towards development firmware

##Commands Once the SPI mode has been selected, the following commands are available :

• 0b00000000 Return to main mode. Returns BBIO1
• 0b00000010 Read a packet.
• 0b00000011 Set CAN ID.
• 0b00000100 Disable filter (accept all packets).
• 0b00000101 Enable filter.
• 0b0000011x Set filter value.
• 0b00001xxx Write CAN packet.

##Command details ###Read Packet (0b00000010) Once the command has been issued, Hydrabus will send a status byte (0x01 if success, 0x00 otherwise). If request is successful, The following data will be sent :

Byte 1           2          3          4          5         6        ...
|----------|----------|----------|----------|----------|----------|------...
   [                 CAN ID               ]   [length]   [data ...

[CAN ID] is always 4 bytes little-endian (to support either standard or extended IDs). [length] is the number of data bytes [data] is between 0 and 8 bytes long

###Set CAN ID (0b00000011) This command must be followed by 4 bytes, representing the identifier further written packets must have. This command always takes 4 bytes and accepts standard and extended IDs.

###Filter commands By default, Hydrabus does not accept any packets until a filter is set. The filter is based on the packet identifier. The following commands will take care of the filter setup.

####Set filter value (0b0000011x) Two slots are available (with x either 0 or 1). This command takes 4 bytes representing the identifier to accept.

This commands returns 0x01 if successful, 0x00 in case of error.

####Disable filter (0b00000100) Disables the filter. All packets will be captured by Hydrabus once this command is sent.

This commands returns 0x01 if successful, 0x00 in case of error.

####Enable filter (0b00000101) Enables the filter. All packets matching the filter will be captured. All other will be discarded

This commands returns 0x01 if successful, 0x00 in case of error.

###Write packet (0b00001xxx) In this mode, the last 3 bits of the command define the number of bytes to write (from 1 to 8) (Command 0b00001000 will send 1 byte). Once this command has been sent, Hydrabus expects the according number of data bytes to be sent.

This commands returns 0x01 if successful, 0x00 in case of error.

##Example script The following Python script can be used to query the vehicle speed and current RPM

import serial
import time

# See https://en.wikipedia.org/wiki/OBD-II_PIDs for information about the OBD2 queries / responses

def rdpkt():
    #Send read command
    ser.write('\x02')
    #Get read status (0x01)
    ser.read(1)
    can_id = int(ser.read(4).encode('hex'), 16)
    length = ord(ser.read(1))
    data = ser.read(length)
    return (can_id, data)

ser = serial.Serial('/dev/hydrabus', 115200)

# Open binary mode
for i in xrange(20):
    ser.write("\x00")
if "BBIO1" not in ser.read(5):
    print "Could not get into bbIO mode"
    quit()

# Switching to CAN mode
ser.write('\x08')
if "CAN1" not in  ser.read(4):
    print "Cannot set CAN mode"
    quit()

# Set CAN ID to 0x7DF
ser.write('\x03\x00\x00\x07\xdf')
if ser.read(1) != '\x01':
    print "Error setting ID"
    quit()

# Set filter to 0x7E8
ser.write('\x06\x00\x00\x07\xe8')
if ser.read(1) != '\x01':
    print "Error setting filter"
    quit()

while 1:
    # Send Query RPM request
    ser.write('\x0f\x02\x01\x0c\x55\x55\x55\x55\x55')
    # Read the transmission status (0x01)
    ser.read(1)
    # Retrieve response
    can_id, data = rdpkt()
    print data.encode('hex')
    #decode retrieved data
    rpmdata = int(data[3:5].encode('hex'), 16)/4

    # Sent Query speed request
    ser.write('\x0f\x02\x01\x0d\x55\x55\x55\x55\x55')
    # Read the transmission status (0x01)
    ser.read(1)
    # Retrieve response
    can_id, data = rdpkt()
    speeddata = int(data[3:4].encode('hex'), 16)

    print str(rpmdata)
    print str(speeddata)

    time.sleep(0.5)