How much is your CAN expansion board for the MBED?
I'm not sure what the difference is between the LPC1769 that you
recommend and the LPC1768 that MBED lists as currently available. One
obvious difference is that the LPC1769 is about US$118. The LPC1768
is $49
http://mbed.org/handbook/Order
My concern is that by the time you make the CAN expansion board, with
all the costs associated with that, you might as well put the main
CPU on the same board and not be stuck buying a retail platform.
Buying two boards is surely going to cost more than one, unless there
is something tricky like radio antenna design involved.
As for PIC versus ARM or even AVR or MSP430, it doesn't really matter
what the processor is. All of these CPU chips have $49 or even $5
(MSP430) evaluation boards and device support libraries.
Brian Willoughby Sound Consulting
On Sep 2, 2013, at 04:11, Mastro Gippo wrote:
Hi Mark, I'd like to throw my 2 cents to the discussion. I'm a professional developer specialized in automotive bus reverse
engineeging, in the past I worked for an automotive diagnostic
company and later for another company that developed electric car
conversion kits, and now I'm the technical director @ eV-Now!
foundation Italy. A while ago I was developing an open source ECU that would allow
anyone to do the CAN bus study with the CAN-USB function and then
program the same device to be an ECU emulator to simulate the
presence of a combustion engine in a converted electric car.
Unfortunately, the project was put on standby for various reasons.The board, as you can see in the picture, is just an expansion
board for the awesome MBED project (www.mbed.org ) and features an
sd card slot, 2 CAN transceivers, an ethernet port and an USB
device port. The MBED is awesome because it offers a lot of cool
libraries and even a ready to use and free RTOS; there is even a
library to connect a 3G modem to the usb host port of the mcu. The
compiler is online and allows an easy management of the project
with an integrated cvs system, and if you don't like it, switching
to the offline (proprietary :( but some open source alternatives
based on gcc are already available) IDE is as easy as downloading
the source file. A demo board that is fully compatible with the
MBED is available from http://www.embeddedartists.com/products/ lpcxpresso/lpc1769_xpr.php , and that includes a programmer and
debugger for less than the price of the PICKIT alone. I know that switching from a well known platform to ARM may seem
like a very hard choice, I was a PIC lover too, but the MBED
library greatly reduces the effort of porting the code to the new
device. For example, adding an usb serial port is this easy:#include "mbed.h"
#include "USBSerial.h"
//Virtual serial port over USB
USBSerial serial;
int main(void) {
while(1)
{ serial.printf("I am a virtual serial port\r\n");
wait(1);}
}
So, IMHO, basing the OVMS v3 on the LPC1769 will solve the code
space problem and transform it into an integrated CAN bus
developing tool, providing some cool features at the same time like
more power an memory, sd card data logging and dual CAN channels,
for a price per MCU just slightly higher than the PIC solution.
Another advantage is that we can develop a nice GUI that will help
the user for the initial configuration of the SIM card connecting
the OVMS to the USB port.On the topic of the protocol, I agree on the CAN232 data format, I
have that device too and all the software I've written is
compatible with that protocol API (I may consider sharing some in
the future, but it's very hacked together and specific for my job).
Also, friends from the linux community have already integrated the
support on the socketcan driver, and provided a very nice
comparison of different devices APIs here: ftp://ftp.heanet.ie/ disk1/sourceforge/s/so/socketcan.berlios/SLCAN-API.pdf I think that it will be a breeze to implement that protocol, and I
can help making it happen for very cheap (or even for free if I
find some spare time and motivation), on the mbed platform.Let me know if you need a PCB to test, I have some spare ones that
you can solder components on, but as (I seem to understand that)
you are based on hong kong, it may be cheaper to reproduce them
locally from gerbers than to ship them from here.Regards
Cristiano
Il giorno 29/ago/2013 03:25, "Mark Webb-Johnson" <mark@webb- johnson.net> ha scritto:
P.S. What I would really like to do is get the OVMS CAN-USB
adaptor working, and then give those out in large quantities. The
more people decoding vehicle CAN communications, the more cars
become open vehicles. But, to do that I need some one / people to
step forward and help with this. The China manufacturer is
standing by and asking me for the circuit diagram, but I've got
too much on my plate at the moment to take on the CAN-USB hardware
and firmware as well. Using a PIC32 microprocessor (with built-in
USB support), and MCP2551 CAN controller, we can do this for a
materials cost perhaps around US$30 (vs US$150 retail for the
cheapest commercial units). I'll send out a separate 'appeal' for
this, and see if anyone will step forward to help.