Design of CAN node based on 32-bit ARM7

CAN bus is one of the most promising field buses. It is widely used in industrial control, automotive electronics, security and other fields due to its excellent performance. Designing the CAN-bus communication interface is a very important link, and the correct operation of the equipment is closely related to it. As shown in Figure 1, an actual CAN-bus communication unit circuit diagram is given. The circuit structure is: LPC2119 (32-bit ARM7 chip with internal integrated CAN controller) + isolated CAN transceiver (CTM Module).


Figure 1 CAN-bus communication unit schematic diagram
LPC2119/2129/2194 processor contains 2 or 4 CAN modules, which can support the operation of multiple CAN buses at the same time, so that the device can be used as a gateway, switch, router of multiple CAN buses in industrial or automotive applications. The biggest feature of PHILPIS's LPC2119/2192/2194ARM7TDMI-S processor that distinguishes it from the LPC2214/2124 processor is the built-in CAN controller. As shown in Figure 1.1, a CAN node circuit based on LPC2119 is given. For the LPC2119 chip, the minimum system requires two sets of power supplies, reset circuits, and crystal oscillator circuits. The P0.14 pin is connected to a pull-up resistor (a resistor connected to the positive power supply) to disable the ISP function. The circuit uses an isolated CAN transceiver module to ensure that the controller can operate normally when the CAN bus is severely interfered.

CAN controller sends sample program

    
 
   
int main()
    
       
       
Data length
Remote frame, data frame flag
Standard frame, extended frame flag
Frame
First four bytes of data
Last four bytes of data
End initialization
       
       
              
              
                     
       
}
       The above is a CAN node composed of LPC2119+CTM isolated CAN transceiver, which introduces the advantages of isolated CAN transceiver: simplified design, stable and reliable, and can achieve complete independence and isolation of each node on the CAN bus in terms of electrical and power supply. The software design part briefly introduces the CAN message sending process and some routines based on the FullCAN function library.