Version 38 (modified by ilya687, 4 years ago) (diff)

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

Xport AR (image)

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:

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,
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.

Xport AR (schematic)

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:

Hardware Monitor (block diagram) Hardware Monitor (schematic)

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.

RS232 Level shifter (block diagram) RS232 Level shifter (schematic)
RS232 Connections (schematic)

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.

Solid State Relays (schematic)

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.

Attachments (9)

Download all attachments as: .zip