EZKIT lite board modifications

In order to run the PC/FlexNet EZKIT.EXE driver, you need to

• download one of the TNC*.EXE files (included in the driver package ezkit.zip) or burn an EPROM with the contents of one of these files (you need to convert it into an EPROM image with the Analog Devices PROM Splitter utility)
• make a small modification to the EZKIT board

This document describes why there has to be such a modification and how to do it.

Why does the hardware have to be modified?

The EZKIT board does not have a dedicated hardware UART to communicate with the PC, it has to emulate such a hardware UART in software. This costs a lot of performance. Analog Devices implemented such an UART by polling the input line very often - three times a bit.

My scheme still has to poll the input line, but I offloaded the sampling of the input line to the SPORT hardware. After the SPORT has sampled the input line 15 times, an interrupt is generated and software examines the UART input samples and decodes them into the RS232 bytes. This scheme still has to do things in software, but instead of servicing 3 interrupts per serial port bit, my scheme only has to serve 1 interrupt per 5 serial port bits!

To summarize: This small modification to the board cuts the software serial port overhead drastically.

What's actually changed?

The TFS1 pin (52) is originally connected to the DR1 pin (55). Since my scheme enables the serial port, TFS1 changes its function and becomes an output. This collides with the RS232 buffer. The modification now involves cutting the trace between TFS1 and DR1 and replacing it with a 10k resistor. See the following pictures for a schematic diagram of the modification and a picture of the modification.

Does ADI software still work?

Yes, the modification is compatible to Analog Devices' software. That's what the resistor is for. My software also runs without the resistor (but not without cutting the trace)