Kirk Wallace wrote: > There is a ModBus feature in Classic Ladder, but it seems to me that an > HAL component specifically for the ModIO peripheral would be useful. > ModBus may be a standard, but peripherals that use ModBus vary widely. > My thinking is that each peripheral needs its own HAL component that > provides HAL pins covering the peripheral's features. ModBus would be > handled in the background. Handling multiple peripherals may be an > issue, but handling a single unit per serial port should be "easy" for > someone comfortable with writing software. I started work on this a > while back, but I have not had time to get back to it. >
Hi Kirk, There are 2 parts here. The Modbus interface basically transfers registers or discretes between a Master (EMC) and Slaves(ModIO). You can almost look at it as shared memory between the master and slave. What EMC does with the data that it receives via the interface has nothing to do with the Modbus Standard. EMC requires a Modbus Master module to be implementd. There are a number of opensource projects that could be used to achieve this. There would then need to be a way of scheduling the transfer of data between each slave and the Master. The schedule would contain the sub-address of the slave, the registers to be read or written, and the rate that the transfer is to occur. The Data from the slaves could be placed in a register array (1 array for each transaction). The 2nd part is device specific and is how you get EMC to interact with the slave through the register transaction arrays. This is where the HAL comes in to play? The idea is that if you wanted to control a discrete output on a PLC, you would set up a transaction to write a value from the array to the register(s) in the PLC. This would be specified at a rate appropriate to the output, say 5Hz, 25Hz, etc. Then if EMC set the value in the register array, it would be transferred to the PLC, turning on the output. Cheers, Peter. ------------------------------------------------- http://www.homanndesigns.com ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
