Practice data transfer over the CAN bus using the following procedures:
Step 1
Use a pair of insulated wires about 20 m long. Connect the CAN_H pins of two demo boards (e.g., the SSE256 or Dragon12 demo boards) with one wire and connect the CAN_L pins of both demo boards with another wire. Connect both ends of these two wires together with 120-Ω resistors (SSE256 has terminating resistors on board). The circuit connection is shown in Figure L13.1.
Step 2
Write a program to be downloaded onto one of the demo boards (called board A) that performs A/D conversion 10 times every second. Use the on-board potentiometer to generate a voltage to be converted. Send out the A/D conversion result over the CAN bus every 100 ms. Use the letter Was the identifier of the data frame. (Use the timing parameters computed in E13.4 for the SSE256 demo board.)
Step 3
Write a program to be downloaded onto another demo board (called board B). This program will send out the number of data frames received so far over the CAN bus. This program will use the letter R as the identifier. After the number reaches 99, the program will reset the number to 0 and start over again. Each digit of the decimal number is encoded in ASCII code.
Step 4
Board A will display the number received over the CAN bus on eight LEDS in BCD format.
Step 5
Board B will display the received A/D result in an LCD display.