General

This RS232 / CAN port DIN rail device can be used to monitor and control a CAN network 
for 11 bits and 29 bits CAN ID's via its RS232 interface.
The new device is ready to work on its factory defaults.

It receives CAN format messages on its RS232 input and sends these directly to the CAN bus.
With its identifier filter, it checks CAN messages on the CAN bus. Matching messages will be transmitted over the RS232 interface.

Specially formatted messages are used to control the RS232 baud rate, CAN baud rate and filter settings via the RS232 interface. These messages use 2 of the reserved (11 bit) CAN identifiers; 2034  and 2035.

From version  2.00 up, this RS232 / CAN port can handle standard and extended CAN frames (with 11 bit or 29 bit identifiers).

V2.01 automatically stops the application if the configuration is read or changed. In fact, the only commands that will not stop the application are 'Start' and 'Get status'

There is a command shortlist table for faster reference.

CAN message format

A CAN message (as seen by the user) exists of 4 fields:

1. Identifier (ID, 11 or 29 bits). Allowed range for 11 bits ID is 0 - 2031, reserve range 2032 - 2047
2. Remote Transmission Request (RTR, 1 bit). Used by some applications to request a message
3. Data Length (DL, 4 bits). Allowed range 0 - 15. Indicates the amount of following data bytes
4. Data. 0 - 8 bytes with application dependent data

When the RTR bit is high, the Data Length is (unmodified) ignored and no data bytes are sent with the message.

When the Data Length is greater then 8, it is treated as if it was 8.

This version of the RS232 / CAN port has 2 modes of operation.

1. STANDARD MODE:
   • Only standard CAN messages (with 11 bit identifiers) can be handled.
   • The filter can enable/disable each of the 2048 possible identifiers
   • RS232 format uses 2 characters to represent the ID, RTR and DL fields.
   • Standard mode is the almost the same as with version 1.02.
   • Maximum CAN bus speed is 1000 kBAUD
     
2. EXTENDED MODE:
   • Standard (11 bits ID) and extended (29 bits ID) CAN messages can be handled
   • The standard filter is the same as in standard mode (every ID can be enabled/disabled)
   • The extended filter has:
     • one bit mask / ID settings to enable a group of identifiers to pass through
     • one global bit mask to ignore some bits in the received ID (before looking up in the table)
     • one table with max. 64 ID's to pass through
   • RS232 format uses 3 or 5 characters to represent the ID, RTR and DL fields.
   • Maximum CAN bus speed is 500 kBAUD (a higher speed may cause internal CAN controller overrun)

Special commands given via the RS232 input of the device are used for configuration, status and control. These commands always use the standard mode RS232 message format, even when the device is put into extended mode.

Filter

The message ID filter works differently for standard (11 bits ID) or extended (29 bits ID) messages:

STANDARD MESSAGE:

• The (11 bits) ID of every incoming standard CAN message is checked against the 2048 bit filter table (using the ID as index). If the corresponding bit in the filter is set, the CAN message is put in the RS232 transmit buffer, using the standard mode or the extended mode (11 bits) RS232 message format.

EXTENDED MESSAGE

1. A bitwise AND of the ID with the 'extended ID mask' is performed
2. The result of this operation is compared with the 'extended ID compare'
3. If there is a match, the message is put into the RS232 buffer, using extended mode RS232 message format with 5 bytes for the ID,RTR,DL fields.
   
4. A bitwise AND of the ID with the 'extended global ID mask' is performed
5. The result of this operation is compared against the 64 ID's in the ID table
6. If there is a match, the message is put into the RS232 buffer, using extended mode RS232 message format with 5 bytes for the ID,RTR,DL fields.

Standard mode RS232 message format (also used for commands to RS232 / CAN port)

The first 3 fields of the CAN message are packed in the first 2 bytes of the RS232 message:

76543210
IIIIIIII

765
III

4
R

3210
LLLL

Extended mode RS232 message format

The first 3 fields of the CAN message are packed in the first 3 or 5 bytes of the RS232 message:

Standard message, with 11 bits ID:

76543210
0000LLLL

7
0

6
x

543210
000III

76543210
IIIIIIII

Extended message, with 29 bits ID:

76543210
0000LLLL

7
1

6
x

543210
0IIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
IIIIIIII

The SF field selects the standard 11 or extended 29 bits identifier.

Although DL field can have a value from 0-15. Any value > 8 will be treated as 8.

When the RTR bit is set to one, no data is expected; even if the DL field indicates that there is....

All RS232 messages are transmitted / received with  8 data and 1 stop bit.
The Baud rate can be configured..

A ten second time-out is used when receiving RS232 messages (message is canceled when not completed within 10 seconds), this is quite long because our beloved Windows may sometimes be doing other things for a while.

To be able to synchronize a crashed application, the device ignores the first byte when its value is 255 (all ones).
Sending 12 characters of all ones guaranties that the device sees the first non 255 byte as a valid first byte.

To synchronize the RS232 stream to the PC, the hardware RTS output of the PC (CTS input of the device) can be used.
When inactive (< -5V) the device does not start transmitting a new message over the RS232, although it finishes the message in progress.

When for some reason the CAN bus is so busy that the device cannot send CAN messages, it de-activates its RTS output (CTS input of the PC) to stop buffer overflow / lost messages (from PC to CAN). When this happens (RTS inactive) it is still possible to send the special RS232 / CAN port commands, by ignoring the handshake line.

When too many CAN messages are received (too many ID's enabled or messages are generated too fast), an internal messages lost counter is incremented. A special RS232 command is sent when this occurs for the first time. The counter can be read with a special RS232 command.

Example (standard mode)

We want to transmit a CAN message with CAN ID 1000, RTR = 0 and 3 data bytes (containing the ASCII characters 'CAN').

The first 2 bytes of the message have to be calculated: (ID * 32) + (RTR * 16) + DL. In our example this will be 32003, which is 7D03 hexadecimal.

5 bytes will have to be transmitted via the RS232 (all byte values are given hexadecimal).

Example (extended mode)

We want to transmit a CAN message with CAN ID 12345678h, RTR = 0 and 3 data bytes (containing the ASCII characters 'CAN').

8 bytes will have to be transmitted via the RS232 (all byte values are given hexadecimal).

Special commands

To be able to configure the RS232 / CAN port,  special commands are used.
These messages always are using the standard mode RS232 message format, but using the reserved CAN ID's.
These messages will not be transmitted over the CAN bus.
These messages are executed even when the RTS handshake output of the device is inactive.

How to get connected can be found here.

Set RS232 Baud rate

There is no reply to this message.

This command sets the RS232 speed that will be used in further RS232 communication 
(the setting is stored in EEPROM, factory default is 9600 Baud).

When this command is given, the device is stopped,  (see stop command).

NOTE: after this command a delay of at least 10 mS is needed before next command can be handled (internal RS232 initialisation).

Set CAN Bus Speed

There is no reply to this message.

This command sets the CAN bus speed that will be used in further CAN communication 
(the setting is stored in EEPROM,  factory default is 50 kBaud).

When this command is given, the device is stopped,  (see stop command)

Get CAN Bus Speed

The device replies with:

Set standard Filter

In order to get only the (11 bit ID) CAN messages of interest, a CAN ID filter table can be set up to enable the CAN messages to receive.
This CAN ID filter table contains 1 bit for each CAN ID. The table is 256 bytes long (256 * 8 bits = 2048 ID's).

Setting up the table requires up to 64 messages to the device:

Some ID to byte/bit position examples;

The device replies with the echo of the command.

This table will be stored in EEPROM memory, factory default is all bits set.
This storing is done in background, so the 64 setup messages can be sent without delay.

When this command is given, the device is stopped,  (see stop command)

Fill Standard Filter

In order to enable or disable all CAN ID's at once, the fill filter command fills the whole filter with the same value:

The value of the data byte is copied into all 256 locations of the standard (11 bits) ID filter

The device replies with the echo of the command:

Directly after the fill filter command, the user can send one or more Set filter commands. This makes it possible to enable just one ID with only 2 messages (fill filter with all zeros, set filter with just one ID enabled at the desired index).

The table will be stored in EEPROM memory. This storing is done in background., so the fill / set messages can be sent without delay.

The filter setting is used in further CAN communication.

When this command is given, the device is stopped,  (see stop command)

Set Extended Filter

In order to get only the CAN messages of interest, a CAN ID filter table is set up to enable the CAN messages to receive.
Setting up the table requires up to 64 messages to the device:

76543210
000IIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
IIIIIIII

The device replies with the echo of the command

This table will be stored in EEPROM memory

This storing is done in background, so the 64 setup messages can be sent without delay.
The storing will start 100 mS after the last Set Filter command is given.

The filter setting is used in further CAN communication.

When this command is given, the device is stopped,  (see stop command)

Fill Extended Filter

When less then 64 ID's are to be programmed in the filter, the user should give a Fill Extended Filter command with Data set to 0xFF. Directly after the fill filter command, the user can send one or more Set extended filter commands. This makes it possible to enable just one ID with only 2 messages (fill filter with all 0xFF, set filter with just one ID enabled at the desired index).

The value of the data byte is copied into all 256 locations of the ID filter

The device replies with the echo of the command:

Directly after the fill filter command, the user can send one or more Set filter commands. This makes it possible to enable just one ID with only 2 messages (fill filter with all zeros, set filter with just one ID enabled at the desired index).

The table will be stored in EEPROM memory. This storing is done in background., so the fill / set messages can be sent without delay.

The filter setting is used in further CAN communication.

When this command is given, the device is stopped,  (see stop command)

Set message ID filters

This command sets up one of the three parameters for the extended CAN message mask filters.

76543210
000MMMMM

76543210
MMMMMMMM

76543210
MMMMMMMM

76543210
MMMMMMMM

76543210
000IIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
000MMMMM

76543210
MMMMMMMM

76543210
MMMMMMMM

76543210
MMMMMMMM

These parameters will be stored in EEPROM memory

The device replies with the echo of the command.

When this command is given, the device is stopped,  (see stop command)

Get Filter

The filter settings can be read with this command:

The index value must be in the range 0 - 63, 65-128, 130-132

The device replies with:

76543210
000IIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
000MMMMM

76543210
MMMMMMMM

76543210
MMMMMMMM

76543210
MMMMMMMM

76543210
000IIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
IIIIIIII

76543210
000MMMMM

76543210
MMMMMMMM

76543210
00000MMM

76543210
MMMMMMMM

When this command is given, the device is stopped,  (see stop command)

Get Status

Read some internal status of the device:

The device replies with:

Start

Start receiving CAN messages.

The device replies with the echo of the command. This can take up to 5 seconds when internal EEPROM programming is still busy (just after the filters are updated)

Only after this command is given or the start at power on configuration is set, the device will relay CAN messages to its RS232 output.

Stop

Stop receiving CAN messages, clear all RS232 message buffers, some status bits and the Lost Messages counter.

The device replies with the echo of the command:

RS232 speed, CAN speed, filter settings and EEPROM programming is not affected by this command. EEPROM checksum is re-checked.

Start at  power on

This command sets an internal EEPROM bit, when this bit is set, the device will start relaying CAN message after power on (no start command needed). This is the factory default.

The device replies with the echo of the command:

When this command is given, the device is stopped,  (see stop command)

No Start at power on

This command clears an internal EEPROM bit, when this bit is clear, the 6293 will NOT start relaying CAN message after power on (no start command needed).

The device replies with the echo of the command:

When this command is given, the device is stopped,  (see stop command)

Reset defaults

This command executes a  stop command, then re-programs the EEPROM to some of the factory defaults.

The device replies with the echo of the command, after the re-programming is finished (can take up to 5 seconds).

Node has to be re-started (at 9600 Baud RS232 speed) by a power cycle or a start command.

When this command is given, the device is stopped,  (see stop command)

Activate extended mode

This command sets an internal EEPROM bit, when this bit is set, the 6293 will work in extended mode: the RS232 message format and the filter are different. The factory default is no extended mode

The device replies with the echo of the command. The filter may have to be setup after this command

When this command is given, the device is stopped,  (see stop command)

Activate standard mode

This command clears an internal EEPROM bit, when this bit is set, the 6293 will work in standard mode: the RS232 message format and the filter are different. This is the factory default

The device replies with the echo of the command, and then switches to extended mode.

When this command is given, the device is stopped,  (see stop command)

Factory defaults.

When a RS232 / CAN port is new, or after the 'reset defaults' command, some or all of the following settings are stored in EEPROM:

How to get connected and how to use the commands

After power on the device is initialized according to the  EEPROM settings for the RS232 speed, the CAN speed, the filter settings and the Start at power on bit.

How to get connected:

1. De-activate your RTS output (CTS input of device). This disables relaying CAN messages to the RS232 output.
   
2. Initialize the RS232 PC port with your standard application communication speed (or 9600 Baud if the device is still in its factory default)
   
3. Send 14 characters FFh to the device to be sure any pending message is flushed OR wait 10 seconds (when waiting 10 seconds it is guaranteed that no illegal CAN message will be send over the CAN bus)
   
4. Send the Stop command to the device and wait for the reply.
   
5. When needed, initialize the RS232 speed, CAN speed, filter settings and Start at power on setting, activate the RTS output and send the Start command.

How to use the commands:

• Setting up the standard (11 bit ID) filter:
  There are several simple ways to do this when only a few ID's have to be enabled, but here a method is described that will always work.
  
  Setup the complete filter setting somewhere in your applications RAM (it's an 256 byte long byte array):
  • Fill the 256 byte array with zero's
  • For every ID to be enabled set one bit in the array:
    Index = ID shifted right 3 bits (0..2031 will be 0..253)
    Bit number = ID AND 7 (lower 3 bits)

  Send the complete filter setting by sending 64 messages to the device
  

• After the device is started (is relaying CAN messages) it is always possible to send the special commands to it, however it is advised to send a Stop command first before changing any configuration (pending CAN messages are lost when the CAN speed is changed).
  
• Even when the CAN bus cannot send messages and the device's RTS output (your application's CTS input) is inactive, it is always possible to send a special RS232 / CAN port command. So your RS232 transmitter should ignore the CTS input when sending a special command.
  
• To synchronize / handshake the received CAN messages, the application can de-activate its RTS output (CTS input of the device). When RTS output is de-activated, any message in progress is finished, and a new one is started when the RTS output is started again.
  This is not true for RS232 / CAN port special (reply) messages, these are send anyway (handshake is ignored).
  
• When the application is started, the device will relay all CAN messages enabled by the filter. It has a 1k buffer to store messages when they are coming in faster then the RS232 can handle. This buffer can handle a burst of 100-500 CAN messages, depending on the amount of data bytes in the CAN messages.
  When this buffer overflows, the internal lost messages counter is incremented. When this happens for the first time, the device sends it status (5 byte message) once over the RS232. So the application's receiver routine has to expect this.

Compatibility

The device can be used by CFG6000/WIN6000 as CAN interface, the same way the 6390/6392 work (using the 6390/6392 interface mode,  see AN002).

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