AVR-Controlled USB-CAN Bus Interface: An Overview
Title: AVR controlled USBCAN Bus Interface
Issue: E
Author: Michael Wolf
Printed: 02/08/2009
A black bar on the left side marks changes since last issue.
Intro
The purpose of this project is a simple and easy to use USB CAN bus interface.
Heart of the circuit is an Atmel AVR ATmega162 microcontroller which controls the
Communication between FTDI FT245BM USB to parallel converter and Philips SJA1000
Stand-alone CAN bus controller.
The SJA1000 is memory mapped into memory space of the AVR, which reduces data and address line handling and increases data transfer speed.
An FT245BM handles all USB communication and provides data transfer from and to PC application. An extra EEPROM can store the multi device template for the FT245BM.
A Philips PCA82C250/251 works as CAN controller interface.
Firmware is written in C, compatible to latest compiler version WinAVR.
Since version v1.07 the firmware is compatible to the CANDIP hardware.
See the CANDIP homepage for more details about the required hardware CANDIP/M162.
Hardware description
IC1
CAN controller interface
Note:
Use a PCA82C251 if 24V compatibility is required.
IC2
CAN controller
IC3
Main microcontroller
The AVR is clocked from the SJA1000 with same crystal frequency (16MHz)
Note:
The pin out shown in schematic is for ATmega162 in SMD TQFP44 package!
IC4
Voltage converter for power supply via CAN bus connector
The circuit is also powered via USB via D3.
IC5
USB communication controller
IC6
EEPROM for multi device template
A template is needed if more than one of the same device is connected to a PC.
JP1
Jumper for CAN bus termination
D1
Red LED for error indication
Blinks if an error was detected by SJA1000.
Continuous light if a bus error was detected.
D2
Green LED for CAN traffic indication, both Rx and Tx.
D3
Power supply via USB connection. This diode must be a low drop version!
The diode is just a safety feature but reduces the voltage for the main
Issue: E
Author: Michael Wolf
Printed: 02/08/2009
A black bar on the left side marks changes since last issue.
Intro
The purpose of this project is a simple and easy to use USB CAN bus interface.
Heart of the circuit is an Atmel AVR ATmega162 microcontroller which controls the
Communication between FTDI FT245BM USB to parallel converter and Philips SJA1000
Stand-alone CAN bus controller.
The SJA1000 is memory mapped into memory space of the AVR, which reduces data and address line handling and increases data transfer speed.
An FT245BM handles all USB communication and provides data transfer from and to PC application. An extra EEPROM can store the multi device template for the FT245BM.
A Philips PCA82C250/251 works as CAN controller interface.
Firmware is written in C, compatible to latest compiler version WinAVR.
Since version v1.07 the firmware is compatible to the CANDIP hardware.
See the CANDIP homepage for more details about the required hardware CANDIP/M162.
Hardware description
IC1
CAN controller interface
Note:
Use a PCA82C251 if 24V compatibility is required.
IC2
CAN controller
IC3
Main microcontroller
The AVR is clocked from the SJA1000 with same crystal frequency (16MHz)
Note:
The pin out shown in schematic is for ATmega162 in SMD TQFP44 package!
IC4
Voltage converter for power supply via CAN bus connector
The circuit is also powered via USB via D3.
IC5
USB communication controller
IC6
EEPROM for multi device template
A template is needed if more than one of the same device is connected to a PC.
JP1
Jumper for CAN bus termination
D1
Red LED for error indication
Blinks if an error was detected by SJA1000.
Continuous light if a bus error was detected.
D2
Green LED for CAN traffic indication, both Rx and Tx.
D3
Power supply via USB connection. This diode must be a low drop version!
The diode is just a safety feature but reduces the voltage for the main