Servo - October 2012

another MRF24J40MA data radio. To keep the sensor-generated bits from piling up in the bit bucket, I’ll attach the remote PIC18F4620 to a device server.

Device Server??

That’s what I said. A device server is an electronic module that accepts a non-IP-based protocol and formats the data represented by the protocol into an addressable IP-based protocol that can travel on a LAN, a WAN, or the Internet. In our design, the non-IP protocol will begin with a START bit followed by eight data bits and a STOP bit. If you added NO PARITY to the aforementioned data stream, you correctly identified our mystery protocol as RS-232. Thanks to the PIC front end, our device server can accept any serial protocol that can be represented in byte format. The device server of choice is offered by the SENA Corporation and is called the NEMO10.

NEMO10 is billed as a single-chip network enabler module. A glance at Photo 1 seems to prove that out. Actually, NEMO10 is a multi-chip serial-to-Ethernet converter housed in a compact DIL configuration. NEMO10 is composed of an 8032 microcontroller, 256 KB of static RAM, program Flash, 64 KB of EEPROM, and a NIC (Network Interface Controller). The NEMO10 is network-ready because it is shipped with a unique burned-in MAC address. The only networking hardware component missing is the Ethernet magnetics module. The NEMO10 is designed to interface with the XFMRS, Inc., XF10BASE-COMBO1-2S Ethernet magnetics/filter combo module which is under the lens in Photo 2.

Like many of today’s modern microcontrollers, the NEMO10’s UART is indigenous to the microcontroller’s silicon. In addition to the Ethernet and

PHOTO 1. The NEMO10 is a compact serial-to-Ethernet converter module designed to interface any RS-232-based device to a LAN or the Internet.

serial interfaces, the NEMO10 provides all of the necessary I/O drive for indicator LEDs.

Using ARP, NEMO10 can resolve hardware (MAC) addresses using known IP addresses. The NEMO10’s ability to act as an ICMP client allows it to respond to a network ping. NEMO10 can request an IP address from a DHCP server and communicate via Telnet. NEMO10 can request an IP address, which infers that it may be able to perform other IP-based client and server functions using IP’s best buddy, TCP. In fact, the NEMO10 can be configured as a TCP client, a TCP server, or a combination of both.

PHOTO 2. You'll need this baby on the other side of the NEMO10 which is designed to interface to Ethernet devices using this XFMRS, Inc., Ethernet magnetics module. There's also a pair of homemade headers in this shot.