Multithreaded Industrial Applications on JK microsystems LogicFlex Controllers

ALT Software (our JK Alliance member in Toronto, Canada) has recently had the privilege of working for a client to assist in implementing a motion controller for the next generation of boat sail making machines.

Contracted to supply firmware for JK microsystems' LogicFlex single board computer, ALT Software developed an application based on a proven legacy design. The LogicFlex controller contains the Intel 386EX microprocessor, flash memory, serial ports, 10mbit LAN, timers, a real time clock and ample I/O ports with bus expansion capabilities in a small 4" by 4" PCB package.

The operating system resembles DOS 3.3, with three internal logical drives and a serial port console. The core DOS is extended with eRTOS, a multithreaded extension, which permits spawning real-time worker threads for concurrent processing. The software is developed with the Borland C compiler configured specifically for producing JK microsystems' large memory model executable programs.

Threads spawned from the main DOS thread are more stable and robust. It was observed that UDP network communication threads are much more reliable if spawned from the main DOS thread. Once all threads are started, the main DOS thread should be put to sleep. Setting all threads to have the same priority and issuing a rt_yield(); (yield to other threads) provided an acceptable means to distribute control between threads and to manage real-time events.

At less than $200.00 per unit these small boards can be considered an alternative to expensive industrial PLC controllers and PC based alternatives for system control applications.