Application Note: Demonstrating CAN with nqbasic

Transcription

1 Application Note: Demonstrating CAN with nqbasic By Carl Barnes, Technological Arts, Inc. May, 0 Hardware used: NCMAX Modules, or NCDX with external user-added CAN transceivers School Board, Docking Module, or similar ( LEDs and a K Ohm resistor => if not using Docking Module or School Board) Wire up the circuit shown in the schematic (at the end of this document). Ensure proper power wiring; otherwise, damage may occur to the electronics. This example shows how to setup the CAN and SCI functions. One module will send the message CANTestx repeatedly, and at the same time display a message on a terminal program to show that it was sent. The other module will receive the CAN messages and display them in a second terminal window to show that they were received. Create the nqbasic project using the code listed below, build it, and load it into each of the two NanoCore modules. Attach one of your NanoCore setups to each COMport, power them up, and run them. Don t forget to connect a cable between the CAN connectors on each setup. For the Docking Module, be sure to place JB and JB jumpers in the - position (i.e. towards the CAN connector, J). For a short CAN cable, the termination resistors are not necessary, so JB jumpers are optional. Launch a terminal program (HyperTerminal, TeraTermPro, or similar) on two nearby PCs. If you have two serial ports, you can use one PC by launching two instances of the terminal program-- one for each COMport. In any case, setup the COMport settings for 00 baud, no parity, -bit data, and stop bit (no handshaking). Reset each hardware setup, and you ll see the menus displayed. In each terminal window, type the digit. Each setup will begin transmitting its message to the other, blinking the LED each time the message is sent. See screenshot, below:

2 CAN Communication Between Two NanoCore DX or MAX Modules ========================================================== Use LED on PT0 or PT with School Board; PT or PT with Docking Module Const LED = PTConst DEL_MSEC = 000 dim S as new SCI (RX_SCI, TX_SCI) dim D as new DIO (LED) dim C as new CAN (RXCAN, TXCAN) //SCI object //Discrete I/O object on LED on PT-pin //Misc variables dim done as new BYTE dim Char as new BYTE dim Index as new byte //Variable to store received characters //Variables for CAN dim canbuffer[] as new BYTE dim txbuffer[] as new BYTE dim rxbuffer[] as new BYTE dim length as new BYTE dim extended as new BYTE dim identlow as new WORD dim identhigh as new WORD //Note that max delay is MAX_WORD () milliseconds (just over minute). sub DelayMsec (in word milliseconds) while (milliseconds > 0) System.Delay (DEL_MSEC) //Delay 000 microsecond to make millisecond milliseconds = milliseconds - ** Print the menu over the serial port. sub PrintMenu () S.SER_Put_string (") Send byte message") S.SER_Put_string (") Send terminal keystroke ") Process the command received on the serial port sub ProcessCommand (in byte cmd) select cmd case '': //Send test message //Init send data for Echo test S.SER_Put_string ("CANtestx -> ") txbuffer[0] = 'C' txbuffer[] = 'A' txbuffer[] = 'N' txbuffer[] = 't' txbuffer[] = 'e' txbuffer[] = 's' txbuffer[] = 't' txbuffer[] = 'x' done =

3 case '': //Send single keystroke from terminal S.SER_Get_char (, Char) S.SER_Put_string (" ") txbuffer[0] = Char txbuffer[] = 0 txbuffer[] = 0 txbuffer[] = 0 txbuffer[] = 0 txbuffer[] = 0 txbuffer[] = 0 txbuffer[] = 0 done = default: done = 0 end select sub CANTest () while (FOREVER) //Send txbuffer - node ID = C.CAN_Send (CAN_TX_BUFFER0, CAN_STANDARD, 0, 0x0, 0,, txbuffer) //Wait for echo C.CAN_Receive (canbuffer, length, extended) //Turn LED ON D.PIN_Out (LED, ON) //Get data out of CAN buffer CAN.CAN_Rec_data (canbuffer, rxbuffer, ) //Echo received data to terminal Index = 0 do Char = rxbuffer[index] Index = Index + until (Index == length) //Turn LED OFF after 00 millisecond delay and repeat DelayMsec (00) D.PIN_Out (LED, OFF) main System.INTS_On () //Setup CAN receive filters (while in initialization mode) BEFORE calling CAN_Setup! C.CAN_Filter (0, 0xFF, 0) C.CAN_Filter (, 0xF, 0x0) C.CAN_Filter (, 0, 0) C.CAN_Filter (, 0, 0) C.CAN_Filter (, 0, 0) C.CAN_Filter (, 0, 0) C.CAN_Filter (, 0, 0) C.CAN_Filter (, 0, 0) //Setup for khz (with mhz crystal), and four -bit receive filters. C.CAN_Setup (0, CANMHZ_BAUD_KHZ, CAN_FILTERS BIT) //Setup UART buffer size and baud rate S.SER_Setup (, BAUD00)

4 //Send banner S.SER_Put_string ("CAN Send test") while (FOREVER) PrintMenu () S.SER_Get_char (, Char) ProcessCommand (Char) if (done == ) CANTest () End if end main //Print menu every time //wait for character to be received //echo it back //check if it is a command Schematic Diagram for CAN Demo Hardware Setup NanoCoreDXC NanoCoreDX U TX VIN RX VSS 0 DTR RESET* VSS VDD AN00 PE0 AN0 PE AN0 PT AN0 PT 0 AN0 PT AN0 PT AN0 PT AN0 PT 0 PM PT PM PT0 PM PM0 PM PM Pin DIP U PCAC0 R 0K RXD TXD Vref Rs GND GND U PCAC0 NanoCoreDX U VIN TX 0 VSS RX RESET* DTR VDD VSS PE0 AN00 PE AN0 PT AN0 PT AN0 PT AN0 PT AN0 PT AN0 0 PT AN0 PT PM PT0 PM PM0 PM PM PM Pin DIP 0 RXD TXD Vref Rs R 0K

5 Schematic Diagram for CAN Demo Hardware Setup NanoCoreMAXC/ 0 NanoCoreMAX U 0 TX VIN RX VSS DTR RESET* VSS VDD PE0 PE PA0 PE AN00 PE AN0 PB AN0 PT AN0 PT 0 AN0 PT AN0 PT AN0 PT AN0 PT PT PT0 VRH PM PM PP0 PM PM0 0 PM PM 0 Pin DIP NanoCoreMAX U 0 VIN TX VSS RX RESET* DTR VDD VSS PE PE0 PE PA0 PE AN00 AN0 AN0 0 AN0 AN0 AN0 AN0 0 PB PT PT PT PT PT PT PT PT0 PP0 PM0 PM AN0 VRH PM PM PM PM 0 Pin DIP 0