CMI8848 expands the capability of the Ethernut boards by providing 8 galvanically isolated digital I/O channels, available at pluggable spring-cage terminal blocks. In combination with an Ethernut board, AC and DC loads and states can be remotely monitored and controlled over a TCP/IP network. The boards are stackable, 2 CMI8848 boards are supported by a single Ethernut board.

8 optocoupler inputs are individually jumper configurable to sense dry contacts or voltages between 3.3 V and 48 V. 8 solid state relay outputs can directly drive high loads like contactors, actuators or motors. All optocouplers and relays are mounted in sockets and may be replaced by pin-compatible components.

This robust board has been in production since 2012. Our in-house quality control procedures guarantee a consistently high level of reliability.

The main characteristics of CMI8848 1.0 add-ons are:

  • Inputs, outputs and mass are galvanically isolated
  • Each channel can be individually configured as either input or output
  • Semiconductorrelais-outputs for max. 48 V, 2.2 A
  • Selectable input level from 3.3 V to 48 V
  • Integrated 5 DC/DC-converter for contact inputs
  • Pluggable clamping contacts for 0.14 to 0.5 mm2 cross-section


A ready-to-use webserver application allows to control and monitor I/Os with a web browser.

In addition, well documented C source code samples are available for all Ethernut boards to help you with your own projects.


Several companies with many years of experience in Nut/OS software and Ethernut hardware offer commercial support.

Furthermore, mailing lists are an important element of this Open Source project, which enable developers to share their experiences and to help one another in problem solving.


The entire source code for the target system, as well as the hardware design, have a permissive BSD licence. This is available for commercial products without any licence fees. In contrast to some other Open Source licence models, there is no obligation to publish your own source code enhancements.


CPU AT91SAM9XE, 200 MHz clock
NOR Flash memory Internal 512 kByte
NAND Flash memory External 1 GByte
Serial Flash memory External 4 MByte
Static RAM Internal 32 kByte
SDRAM External 128 MByte
RTC Hardware (PCF8563T)
Ethernet RJ45 10/100BaseT (LAN8710)
USB USB 2.0 device at Mini-B and host at Standard-A receptacle
RS-232 1 x 9-pin DCE, 8-Wire
Memory card SD card / SDIO / Multimedia card socket
Digital I/O 15 configurable GPIO lines with alternate functions
Analog I/O 2 channels with external trigger and reference
Programming 20-pin JTAG
Indicators Power (red), link (yellow), activity (green)
Power supply
Regulator 600 mA switcher (LT1616, LTC3407, LTC4411)
Management ATmega168 CPU
DC input 2.1 mm barrel connector, unregulated 5 to 24 V DC
USB USB Mini-B, 5 V
Ethernet IEEE 802.3af
Consumption < 1 W at 12 V
Battery backup Double layer capacitor for RTC
RS-232, USB 15 kV ESD protection
Ethernet Transformer isolation
Power Supply 1 A replaceable fuse, rectifier bridge, current limiter, thermal shutdown
Operating temperature -20 to 85 °C (-4 to 185 °F)
Storage temperature -65 to 140 °C (-85 to 284 °F)
Humidity 5 to 95 % non-condensing
Safety PCB flammability rating UL94-V-0
RoHS compliance EU directive 2002/95/EC
Dimensions (L x W x H) 98 x 78 x 17 mm (3.86 x 3.07 x 0,67 in)
Weight 75 g (0.165 lb)
Product identification
PCB revision Written in copper on the PCB's backside
Serial number IEEE registered MAC Address on barcode sticker label (Code 128C)


CMI8848 1.0 flyer
03.02.2012 | 0.54 MB | English

CMI8848 1.0 hardware manual
15.02.2012 | 9.18 MB | English

CMI8848 1.0 rev-B schematic
18.08.2011 | 0.15 MB