Tiny Server

Wichit Sirichote, kswichit@kmitl.ac.th

Build a simple device for connecting serial instrument with RS485 or RS232 to the internet.

The device that converts RS485 and RS232 to the ethernet LAN has been developed. The device was built with the Lantronix XPort embedded ethernet server and the industrial standard differential RS485 transceiver, 75176 and the single-end RS232 driver, MAX232. The XPort module provides 10/100 ethernet port and the +3V logic UART. The 75176 and MAX232 are +5V TTL logic. The CMOS buffer, 4050 is used to translate +3V to +5V logic. There is no jumper selection between RS232 or RS485. The receiver pin of the XPort is tied to the both signals from RS232 and RS485 through the use of open collector IC, 7407. The server was tested with TELNET port 1001 and the Fluke 45 multimeter.

Figure 1: The Tiny Server board was built with the Lantronix XPort and the Industrial standard differential transceiver, 75176 and MAX232. The XPort is labeled with MAC address, 00-20-4A-9A-BF-51.

Hardware Schematic

U1 is the embedded device server, XPort. The device is powered by +3.3V voltage regulator U8, TI TPS79533. The MAX232 and 75176 are +5V logic. The CMOS MC4050 is used to convert +3.3V logic to +5V logic. U5 is open collector buffer gate, 7407. It used to convert +5V logic from MAX232 and 75176 to +3.3V logic. U5A and U5B combines the received signal from RS232 and RS485 to the RxD pin of the XPort. This eliminates the jumper selection.

Figure 2: Hardware schematic, click the image to open pdf schematic.


Figure 3: The +3.3V SMD voltage regulator TI TPS79533, sponsered by Texas Instrument.


Figure 4: The Tiny Server in a small plastic box. Shown the 10/100 Ethernet port and RS485 terminal.


Figure 5: Connecting diagram for testing the Tiny Server with Fluke 45 Multimeter.


Figure 6: Pyranometer measured by Fluke 45. The RS232 port of Fluke 45 is tied to the Tiny Server enabling the insolation reading over the Internet. The right-hand photo shows the demonstration on Science Day 2550.



Figure 7: PCB Top Overlay.


Bill Of Materials July 16,2007 11:07:26 Page1
Item Quantity Reference Part
1 1 C1 10uF 10V
2 3 C2,C3,C4 10uF
3 1 C5 .01
4 1 C6 22uF
5 1 C7 10uF 16V
6 1 C8 1000uF 16V
7 3 C9,C10,C11 0.1uF
8 2 C12,C13 0.1uF 
9 1 C14 0.1
10 1 D1 TxD LED
11 1 D2 TxE LED
12 1 D3 RxD LED
13 2 D5,D4 1.5KE7.5CA
14 1 D6 POWER
15 1 D7 1.5KE12CA
16 1 J1 CON3
17 1 J2 +9V DC input
18 3 R1,R2,R3 330
19 3 R4,R8,R10 4.7k
20 2 R5,R7 680
21 1 R6 120
22 1 R9 2k
23 1 S1 TEST CP2
24 1 U1 XPORT module
5 1 U3 4050
26 1 U4 MAX232A
27 1 U5 7407
28 1 U7 75176
29 1 U8 TPS79533
30 1 U9 LM2490
31 1 VB1 SUB-D 9, DB9 male
32 1 V1 BRIDGE
Figure 7: Part List.


Schematic tinyserver.pdf
XPort Technical Docs

11 August 2007