Current projects

I've been toying with a lot of things recently.

Automated builds of AnyIO FPGA Firmwares

I've been helping John Kasunich a little bit on automating the build of all the flavors of AnyIO FPGA firmwares--25 in the last emc2 release--automatically. Presently, the process apparently involves Peter Wallace of Mesa Electronics manually making edits to a few vhd files and repeatedly invoking the build process in the Xilinx ISE gui. Hopefully when we're done the process will be automated, though it may still run for an hour or two (my laptop runs for about two and a half minutes to produce 5i20/SVST8_4.BIT).

Ladder Logic for AVRs

I took a look at Ladder Logic for PIC and AVR (GPL), compiled it with wine-dev and tried to port it to the atmega168 on Arduino boards, but unfortunately I've still got a bug--probably in the setup of timing-related registers. There's not a direct connection to emc here, but I know there are a lot of ladder logic fans out there to whom this might be appealing.

Modbus Slave for AVRs

Then I had a look at freemodbus, a BSD-licensed modbus slave implementation for embedded systems. I did succeed in running that on my Arduino, and got it to communicate with both a standalone modbus master and with emc2's classicladder in TRUNK. I still maintain that making the modbus hardware interface an inseparable part of classicladder is the wrong thing to do, but as long as it's the only generic modbus interface someone's contributed, well, it's better than nothing.

In doing that, I found bugs in freemodbus--its "report slave id" function seems to be broken, not writing a byte count where it should--and in the modbus master library used by emc2 TRUNK's gs2_vfd and in my standalone exercise program--its "report slave id" function is also broken, by hardcoding a probably-incorrect response length. So was its read input registers request, for a similar reason.

Of course, my litany of modbus-related complaints wouldn't be complete without a complaint about the Specification and Implementation Guide for MODBUS over serial line in which they explain on page 13 the inter-byte timing requirements of MODBUS RTU, then immediately say in a "remark" that in fact you should do something almost entirely different.

Having modified both the client and the server of the modbus protocol before they would talk to each other, I'm forced to ask: do either of them talk modbus at all? Good question!
(originally posted on the AXIS blog)

Entry first conceived on 17 December 2008, 2:49 UTC, last modified on 15 January 2012, 3:46 UTC
Website Copyright © 2004-2014 Jeff Epler