Digilent chipKIT Max32¶
To build for the chipKIT-based Vehicle Interface, compile with the flag PLATFORM=CHIPKIT. The chipKIT is also the default platform, so the flag is optional.
The chipKIT VI supports up to 2 of the CAN1, CAN2-1 or CAN2-2 buses simultaneously.
For more details, see the chipKIT’s documentation.
For instructions on flashing a new firmware version to the chipKIT, see the chipKIT firmware programming documentation.
The micro-USB port on the Digilent Network Shield is used to send and receive OpenXC messages. The mini-USB cable on the Max32 itself is only used for re-programming.
On the chipKIT, UART1A is used for OpenXC output at the 230000 baud rate. Hardware flow control (RTS/CTS) is enabled, so CTS must be pulled low by the receiving device before data will be sent. There are a few tricky things to watch out for with UART (i.e. Bluetooth) output on the chipKIT, so make sure to read this entire section.
UART1A is also used by the USB-Serial connection, so in order to flash the PIC32, the Tx/Rx lines must be disconnected. Ideally we could leave that UART interface for debugging, but there are conflicts with all other exposed UART interfaces when using flow control.
- Pin 0 - U1ARX, connect this to the TX line of the receiver.
- Pin 1 - U1ATX, connect this to the RX line of the receiver.
- Pin 18 - U1ARTS, connect this to the CTS line of the receiver.
- Pin 19 - U1ACTS, connect this to the RTS line of the receiver.
UART data is sent only if pin A1 is pulled low (to ground). If you are using a Bluetooth module like the BlueSMiRF from SparkFun, you need to hard-wire GND into this pin to actually enabling UART. To disable UART, pull A1 high (hard-wire to 5v) or leave it floating.
An additional item to consider when using UART: typically you will want to rig the chipKIT to be self-powered (either from an external power source or the vehicle) if you’re going to use UART for adding Bluetooth support. There’s not much point in being wireless if you still need power from USB.
In that case, move the power jumper from the 5v input on the Network Shield to A0 (analog input 0). Instead of using 5v to power the board, the firmware can use it to detect if USB is actually attached or not. The benefit of this is that if you connect USB, then disconnect it, we can detect that in the firmware and stop wasting time trying to send data over USB. This will dramatically increase the throughput over UART.
On the chipKIT Max32, logging will be on UART2 (Pin 16 - Tx, Pin 17 - Rx) at 115200 baud (if the firmware was compiled with DEBUG=1).
The chipKIT has 1 user controllable LED. When CAN activity is detected, the LED will be enabled (it’s green).
Compiling and Flashing¶
Attach the chipKIT to your computer with a mini-USB cable, cd into the src subdirectory, build and upload to the device.
$ make clean $ make $ make flash
If the flash command can’t find your chipKIT, you may need to set the SERIAL_PORT variable if the serial emulator doesn’t show up as /dev/ttyUSB* in Linux, /dev/tty.usbserial* in Mac OS X or com3 in Windows. For example, if the chipKIT shows up as /dev/ttyUSB4:
$ SERIAL_PORT=/dev/ttyUSB4 make flash
and if in Windows it appeared as COM4:
$ SERIAL_PORT=com4 make flash
It is possible to use an IDE like Eclipse to edit and compile the project.
- Follow the directions in the above “Installation” section.
- Install Eclipse with the CDT project
- In Eclipse, go to File -> Import -> C/C++ -> Existing Code as Makefile Project and then select the vi-firmware/src folder.
- In the project’s properties, under
C/C++ General -> Paths and Symbols, add these to the include
paths for C and C++:
- /src/libs/CDL/LPC17xxLib/inc (add as a “workspace path”)
- /src/libs/chipKITCAN (add as a “workspace path”)
- /src/libs/chipKITUSBDevice (add as a “workspace path”)
- /src/libs/chipKITUSBDevice/utility (add as a “workspace path”)
- /src/libs/chipKITEthernet (add as a “workspace path”)
- /usr/include (only if you want to use the test suite, which requires the check C library)
- In the same section under Symbols, if you are building for the chipKIT define a symbol with the name __PIC32__
- In the project folder listing, select
Resource Configurations -> Exclude from Build for these
If you didn’t set up the environment variables from the Installation section (e.g. MPIDE_HOME), you can also do that from within Eclipse in C/C++ project settings.
There will still be some errors in the Eclipse problem detection, e.g. it doesn’t seem to pick up on the GCC __builtin_* functions, and some of the chipKIT libraries are finicky. This won’t have an effect on the actual build process, just the error reporting.