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INTRODUCING THE PACKET WHACKER

Part 1: Hitching a Ride on the Picdem.net
by Fred Eady

Start ý PICDEM.NET ý Whatýs in the PIC NIC Basket? ý Provisions ý The Packet Whacker ý Taking the Demo Out of the Board ý Programming ý Smoke Test ý Where to Go from Here ý Sources and PDF

WHATýS IN THE PIC NIC BASKET?

As I mentioned earlier, if youýve read my NIC articles in Circuit Cellar, youýve already been on a "PIC NIC" with the RTL8019AS. The Realtek NIC provides Ethernet connectivity to support serving web pages and general Internet or LAN communications. To complement the RTL8019AS, a series of LEDs are provided on the PICDEM.NET to display the status of the system and Ethernet connection. In Demo mode using the original PIC16F877, the SYSTEM LED driven by port pin RA4 of the PIC16F877 flashes to indicate that everythingýs connected and powered up OK. A link status LED is present and in default Demo mode flashes on network collisions.

My PICDEM.NET is a revision 4 board, and the status LED defaults to collisions. On revision 5 boards, the status LED lights to show an active Ethernet connection. TX and RX LEDS do what they say they do on both revision levels, indicate transmit and receive activity. Curiously, the TX and RX LEDS are on when nothing is happening and off when indicating activity. Thatýs something Iýll take a look at when I take the PICDEM.NET off road. The NICýs magnetics and the 8-pin RJ-45 Ethernet jack are positioned directly above the RTL8019AS NIC.

In addition to the LEDs that are dedicated to the RTL8019AS NIC, there are a couple of LEDs driven off the PIC16F877 I/O pins that can be used to verify user code by simulating digital output. Instead of hanging real hardware off the PICDEM.NET during development, you simply write to the user-defined LED I/O pin and note the status of the LED. Also, the user-defined LEDs are useful for signaling that a certain area of the program under development has been executed. The LED is used as a sort of breakpoint indicator. The user-defined LEDs are connected to port pins RA2 and RA3 of the PIC16F877. An enable/disable jumper is positioned between the LEDsý anodes and 5 VDC.

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