CAN232 : Controller Area Network (CAN) to RS232

Features Powered by MicroChip PIC18F258 Philips 82C250 Physical Layer RS232 Interface with ASCII Command Interface. Selectable 9600, 19.2k, 57.6k, or 115.2k baud rates. Small form factor. Messages can be event driven (single key command to send or receive) Message can be sent repeatively

The CAN232 uses 10 message objects (1 thru 10) to send and receive CAN messages. This allows for single key send and receive using keys 1 thru 9 and message #10 is the 0 key.

Command Table (click on command to go to detailed description). Certain commands respond to a single ASCII character and do not require a carriage return to execute. Other commands that need parameters are terminated using a carriage return. Carriage returns are denoted using the [cr] notation.

The offline command, F, disables communications. This command does not require the carriage return to terminate the command.

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ONLINE

The online command, O, enables communications. This command does not require the carriage return to terminate the command.

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RESET

The reset command, X, resets the 82527 CAN chip on the CAN232.

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BAUD RATE

The baud rate command is used to view or set the baud rate.

• B[cr] displays current baud rate
• B0[cr] = 1 mbps
• B1[cr] = 889 kbps
• B2[cr] = 800 kbps
• B3[cr] = 727 kbps
• B4[cr] = 666 kbps
• B5[cr] = 500 kbps (default value)
• B6[cr] = 250 kbps
• B7[cr] = 167 kbps
• B8[cr] = 125 kbps
• B9[cr] = 100 kbps
• B10[cr] = 83.3 kbps
• B11[cr] = 62.5 kbps
• B12[cr] = 50 kbps
• B13[cr] = 41.67 kbps
• B14[cr] = 33 kbps
• B15[cr] = 31.25 kbps
• B16[cr] = 25 kbps
• B17[cr] = 20 kbps
• B18[cr] = 10 kbps

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CONFIGURE MESSAGE OBJECT

The configure message object command sets the direction, type, length, and id for a message.

Cobj,dir,type,len,id[cr]

• obj specifies one of 10 message objects from 0 to 9
• dir specifies the direction, either R for receive or T for transmit
• type specifies either S for standard 11 bit identifiers or E for extended 29 bit identifiers
• len specifies the message length for 0 to 8 data bytes
• id specifies the 11 or 29 bit identifier

For example:

C1,R,S,8,0x100[cr] specifies that message object #1 is a receive message, standard 11 bit ID, 8 data bytes and id = 0x100 (hex).

C2,T,S,5,50[cr] specifies message #2 is a transmit message, standard 11 bit ID, 5 data bytes, and id is 50 (decimal).

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SET MESSAGE DATA

Message data is set using this command.

For example:

S1,0,0,55,0,0xaa,0,0,1[cr] sets all 8 data bytes for message object #1.

S1,0,2[cr] sets only the first 2 data bytes for message object #1. The remaining 6 are left unchanged.

Note: To set individual bytes use the Set Message Data Byte command.

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DISPLAY MESSAGE DATA

Message data is displayed using this command.

For example:

D1[cr] displays all 8 data bytes for message object #1.

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HELP

The H command displays the online help.

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SEND/RECEIVE MESSAGE

The ASCII characters 0 through 9 can be used to send or receive a message. If the message has been configured to transmit then the message will be sent. If the message has been configured to receive then CAN232 will display if the message is new and will alos display the data bytes.

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PUT INDIVIDUAL MESSSAGE DATA BYTE

The P command allows writing an individual data byte in a message.

Pobj,b,d[cr] where obj is message object 1 to 10 (0 representing 10), b is the data byte location in the message from 0 to 7, and d is value to write to the data byte.

For example:

P1,0,10[cr] writes decimal 10 to the first data byte of message 1

P9,7,0xa0[cr] writes hexadecimal a0 to the last data byte of message 9

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GET INDIVIDUAL MESSAGE DATA BYTE

The G command allows reading an individual data byte in a message.

Gobj,b[cr] where obj is message object 1 to 10 (0 representing 10), and b is the data byte location in the message from 0 to 7. The value is returned as a decimal value terminated with a carriage return.

For example:

G1,0[cr] reads the first data byte of message 1

G9,7[cr] reads the last data byte of message 9

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MESSAGE SEND TIME

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SET BIT TIME REGISTERS

The SET BIT TIME REGISTERS command allows a user to setup the registers that control the baud rate to values other than the standard values set using the BAUD RATE command. refer to the 82527 Bit Timing Defintions data sheet for more information.

This command is for advanced users and will not be needed in most cases.

Tsjw,brp,spl,tseg1,tseg2 where sjw is the (Re)Synchronization Jump Width, brp is the Baud Rate Prescaler, spl is the Sampling Mode, tseg1 is Time Segment 1, and tseg2 is Time Segment 2.

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READ REGISTER

The READ REGISTER command allows a user to read the value of one of the 82527 registers. Refer to the 82527 data sheet for further information.

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WRITE REGISTER

The WRITE REGISTER command allows a user to write a value to one of the 82527 registers. Refer to the 82527 data sheet for further information.

Wb,d[cr] writes the 1 byte value (range 0 to 255 or 0 to 0xff)   in d to register b (0 to 254 or 0 to 0xfe). Do not write to register 255 (0xff).

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VERSION

This command displays the version information, terminated with a carriage terminated.

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