RE: Error recovery using MCP2515 can controller
"John Dammeyer" <[email protected]>
| Newsgroups | gmane.comp.hardware.bus.can |
|---|---|
| Message-ID | <[email protected]> |
>Hi Chuck, > In my application (signal control for 7.5" gauge ride-on railroads) there > are several classes of messages: ... > > Object Status: These messages are sent once per second (or upon 'state' > change .. on/off, etc.). Good. It doesn't look like you are using 'TOGGLE' messages. Messages controlling outputs should always be ON or OFF, never TOGGLE. That's due to an actual bug in the CAN protocol that could allow under very rare circumstances a message to be correctly acknowledged by the receiver but the ACK missed by the transmitter so it resends. That results in two messages on the bus both correctly ACK'd from the receiver's perspective. You get a double set of 'toggle an output' message and the output doesn't change. > Are you the same John Dammeyer that is on the MACH CNC users email list? Yes that's me and I'm the designer of the Electronic Lead Screw (ELS) kit which BTW, has a spot for a CAN driver on it that is an alternate use for the X axis step/dir pins. I've even ported Microchip's CANOpen AN945 stack onto it. So far all it does is create a PDO message for key up, down, held events. And it will take a segmented SDO of 40 characters and place that on the 2 line LCD display. Or a menu #. The menu is retrieved, parameters relative to that menu accessed and written into the 40 character menu buffer and then placed on the LCD display. No support for the stepping motor driver or the encoder knob. No real internal behavior like press this key and this happens on the display. It's just a simple CANOpen node and really was more of an exercise in porting the Microchip stack. A client was interested but it's so much easier to buy a display/key unit from RM Michaelides. John Dammeyer "ELS! Nothing else works as well for your Lathe" Automation Artisans Inc. http://www.autoartisans.com/ELS/ Ph. 1 250 544 4950 -- Archives and useful links: http://groups.yahoo.com/group/CANbus Subscribe and unsubscribe at www.vector.com/canlist/ Report any problems to <[email protected]>