DIN rail Pin Description

USB connection shown.  Details on the enclosure at OKW enclosures .

The Ethernet version is software compatible with the ARMweb, refer to those pages for more information.

The USB version uses the standalone ARMbasic compiler on the PC.

Rev 1

25 pins available to the user, 6 of which can be analog inputs, 8 high current drivers, 3 digital IOs, and 8 flexible IOs

The LPC2138 is used with 512K Flash and 32K of SRAM.

Optional connections to USB, 10Mb Ethernet, or RS-485 (with optional isolation)

                                                                       picture shown without screw terminals for clarity

Power Inputs

Board 7-40V DC.  This voltage is reduced with a switching regulator for the 3.3V internal board supply.

High Current Driver (ULN2803 ) 5-50V.  This can be a separate supply from the Board input power, or can be the same supply.  It is a required connection for relay drivers to provide a path for current when the relay coil is turned off, it does not have to be the power supply for the board in this case, but it can be.

For volume customers the power supply can be stuffed to accept a regulated 3.3V supply directly, this is done by omitting the switching power supply and adding an appropriate ferrite bead at L5.


The schematic is too large to include on this page, but is downloaded into the /Program files/Coridium/Schematic directory.   Is also available here..


OKW B6704100  The kits include custom cutouts for either Ethernet or USB connections.  Mechanical drawing for the enclosure is here ,

All the following options can be configured by the user, by optionally stuffing the through-hole components in the DIN rail kit.  Coridium will configure boards when 10 or more are ordered.

6 AD pins

These may configured for 4-20 mA sensors, with resistor dividers, or as digital inputs.  These inputs have diode clamps to 3.3V and GND.

4-20mA sensor --

                                   load 150 ohm SIP into R17

suggested components
  Bourns 4600X Bussed SIP resistor
  Bourns 4100R Isolated DIP resistor

A/D resistor divider --

                   load R15 DIP resistor and R14 SIP with appropriate values

                   AD = Vin * R14/(R14+R15)

                   Source impedance to AD should be less than 10K.


digital IO --

                   load R15 with 100 or 1K


digital IO (pull-down)--

                      load R15 with 100, R14 with 10K


digital IO (pull-up) --

                   load R15 with 100, R14 with 10K


High Current Drivers

These may use a high sink current driver, or configured as digital IOs with optional pull-ups or pull-downs.  The ULN2803 is an array of Darlington transistors that either pull a line low (when the corresponding IO is high) or does not conduct at all.   A typical application is to use these lines to drive a relay, with the opposite end of the relay tied to a power supply.

High Current drive --

               This driver can sink a surge current of 500mA up to 50V, this driver is a ULN2803 .

suggested components 
  TI  ULN2803AN 
  Toshiba ULN2803APG
  STmicro ULN2803A

digital IO --


digital IO (pull-down) --


digital IO (pull-up) --


Flexible IOs

These may be configured as 8 digital IOs (with and without pull-up/pull-down), opto-isolated inputs or outputs, or differential inputs or outputs.  They are arranged in 2 groups of 4 so that there can be 2 opto-isolated input and 2 opto-isolated outputs. 

opto-isolated input --

suggested components 
  Liteon LTV-827 
  Fairchild MCT9001
  Toshiba TLP621-2

opto-isolated output --

same components as above, rotated 180 degrees

bi-directional RS-422 driver --

suggested components 
  National DS75176BN
  TI SN75176AP

bi-directional RS-422 driver with termination --

suggested components 
  Bourns 4600 Isolated SIP resistor

digital IO --


digital IO (pull-down) --


digital IO (pull-up) --


3 digital IOs

These may be configured as straight thru, or with pull-ups or pull-downs

digital IO --

                                         shown with 100 ohm series


digital IO (pull-down) --

                                            shown with 10K pull-down and 100 series


digital IO (pull-up) --

                                           shown with 10K pull-up and 100 series


RTC options

Rev 3

This revision adds the diode and resistor needed for charging an ML2020 battery.   That battery can be mounted on the backside of the board as illustrated below



Rev 2

To connect a battery, remove R23, and use the Vbat via to connect, a resistor-Schottky diode-battery connection (suggested schematic below)

GND and 3.3V are available on either side of C7

A 32 KHz crystal (such as the Citizen CMR200TB32.768KDZFTR)  can be connected at Y2, with the two 22pF startup caps on the bottom/circuit side of the board.