Hardware Description

The new chassis manager uses a completely new set of hardware compared to the older revisions. The design is based around the Lantronix XPort AR module, along with accompanying external hardware for interface to the node. The SDK for this device allows the implementation of custom code which is used to interface and understand CMC instructions. A full schematic of the CM3 is attached as a PDF to this page.

Major Hardware Components

Lantronix XPort AR

The Xport AR is an embedded device server, produced by Lantronix. It runs off of the ​Evolution OS®, combined with the custom software written using the Xport AR SDK. The Xport AR acts as the 'brains' of the CM3, handling all the networking tasks, as well the link between the CMC instruction commands, and the physical interface to the node. It has the following basic features:

Architecture
CPU	Based on the DSTni-EX enhanced 16-bit, 120MHz x86 Architecture
Memory	1.25 MB RAM and 4 MB FLASH
Firmware	upgradeable via FTP,TFTP, Serial Ports, Internal Web Server
Diagnostics	Built in diagnostics and comprehensive statistics
Network Interface
Interface	Ethernet 10Base-T or 100Base-TX (Auto-Sensing)
Connector	RJ45
Layer 3 Protocols	TCP, UDP, IP, ARP, ICMP, SSH, SSL, XML, HTTP, PPP, PAP, CHAP, DNS, SMTP, RSS, DHCP, BOOTP, AutoIP, SNMP, FTP, TFTP, Telnet, CGI
Serial Interface
Interface	CMOS (Asynchronous, 5V Tolerant)
Data Rates	300 bps to 230,400 bps (selectable by 1bps increments)
Characters	7 or 8 data bits
Parity	Odd, even, none
Stop Bits	1 or 2
Control Signals	RTS, CTS, DSR, any PIO
Flow Control	XON/XOFF, RTS/CTS, User Selectable Characters

The GPIOs are used to control the solid state relays used to power the node on/off and reset the node, as well as monitor the 'hardware status', see the next section for details on this.

More information on the Xport AR can be found ​here, and documentation on the device can be found ​here.

Voltage Monitor

The CM3 has a PC voltage monitoring chip installed, the DS1780E. This chip monitors the +5V, +12V, and temperature of the air in the case. The voltage levels are taken from the floppy connector (J2) which feed directly into the chip and communicates that information over I²C to the Xport AR. However the I²C is not active on the Xport AR, and so there is no way to effectively get accurate voltage and temperature data about the node.

The 'status' (i.e. on or off) of the node depends on the voltage levels of the power supply (PS), so as a work around for the lack of I²C support the current hardware version of the CM3 has the 5V line feed directly into one of the GPIO (set as an input) and if that is high the PS is on, and so the node is also on. Hopefully I²C will get some support in the future from Lantronix. Presently R4 and R14 is installed and R8 is left open. If I²C is to be implemented then R4 and R14 would have to be removed by hand, and R8 installed.

The functional block diagram and schematic implementation of the DS1780E are presented here:

RS232 Level Shifter

The RS232 level (MAX3232) shifter takes the TTL compliant voltage levels from the Tx and Rx lines of the Xport AR and converts them to RS232 voltage standards (and vice versa). there is also 2 sets or resistors R15 & R16, and R17 & R18, which correspond to build in crossover or straight through signals. If R15 and R16 are installed then a straight cable is used to connect to the node serial port and if R17 and R18 are installed a null modem (or crossover) cable must be used. This is the sase for revision 4 of the CM3 board, the previous revision 3 had rotary switches rather than 0 ohm resistors. Also note that presently the RTS and CTS signals have to be shorted manually on the 5x2 100mil header in order for serial redirection to work. This was an oversight in the design and will be fixed in the next run.

Solid State Relays

There are two solid state relays (AQV201A) that act as an intermediary to simulate the button press corresponding to a reset and power button for the node motherboard. Important to note, is that the power and reset commands will not work is one of the two output sides of the relays is ties to power or ground, it must be a floating power/closed, and not shorting one pin to ground.

Extra Parts

Part Desc.	Manuf.	Part Number	Link
Power Connector	TE Connectivity	179228-2	​link
Power Connector Pins	TE Connectivity	179227-1	​link
DB9 Ribbon Connector	Amphenol Commercial Products	L17DEFRA09S	​link
Rectangular Ribbon Connector	TE Connectivity	1658620-1	​link
Right angle brackets	Keystone Electronics	621	​link
Jumper Cables (power/reset)	Sparkfun	PRT-10367	​link
4-40 flat screw	McMaster Carr	91500A122
4-40 Pan Head Screw	McMaster Carr	91735A101

Notes on latest delivered run REMOVE the following 0 ohm resistors: R6, R7. They are located under the MAX3232EC chip.