Overview

When considering the requirements of a MODBUS slave system that could be used to support the uSCADA(p) and uMODBUS(m) android software packages, the shortcomings of the original general purpose core have become apparent.

By taking on board was has been learnt thought the development of the first version
of the general purpose core, it was decided to further refine the design by freeing
up as much microcontroller I/O as possible.

In addition to this great care was taken to minimise the I/O required to support
the LCD, Keyboard, Serial communications interface and preset jumper links.

Design & Construction

After a bit of rework the following design was arrived at, as mentioned above the new circuit has a serial port and all spare I/O is made available for project development, additionally there are 8 configuration links and 4 pulse output pins.
 

The circuit when transferred onto stipboard appears as below:

Constructed of the stripboard design was then carried out in order for software development to begin.

A number of I/O support boards were created that allowed the development of software to test the boards functionality and then allow development of the first version of uMODBUS(s) the microcontroller based MODBUS slave system.

Links:

- GPC(Build B Revision A) High Resolution Circuit Diagram(Normal Keyboard)

- GPC(Build B Revision A) High Resolution Circuit Diagram(Reversed Keyboard)

- GPC(Build B Revision A) High Resolution Circuit Diagram(Links Board)

- GPC(Build B Revision A) High Resolution Stip Board Layout