Digi connect ME caught my eyes from very beginning when Digi announced .NET Micro Framework support for this device. The only problem with Connect ME is the 1,27mm pin header connector. Such a small connector is fine for industrial use, but not so much for hobbyist, because it’s almost impossible to purchase it (at least in Czech Republic). And, who wants to solder such a small connector to every hobby-project PCB? In every day use there must be some simple mounting way. For designing custom circuits on breadboard or easy mounting to PCB it’s necessary to have 2,54” pin module. That brings me to idea of some adaptor board for Digi Connect ME. British company Crownhill Associates sells such a adptor board for 10 British pounds. Unfortunately the product is no more available, and shopping is not so challenging as handcrafting!!. It’s important to say, that Digi delivers very good development board for Digi Connect ME, and everyone who is interested should have one. But development board don’t gives you so much freedom as adaptor board.
Figure 1: Digi Connect ME adaptor board PCB
Designing the printed circuit board
Dimensions of the Digi Connect Me is described in the hardware reference manual, so it was quite easy to design basic PCB layout. Modules 1,27mm and 2,54mm are common standards so it was only about connecting appropriate pins. To be honest, there are not to much possibilities how to connect those pins, so my pin-out design is compatible with Crownhill adaptor board.
CAD drawing for PCB and pin-outs is in the DigiConnectME_adaptor_PCB.dwg file. For those who don’t have CAD software, I’ve exported PCB layout into DigiConnectME_adaptor_PCB.pdf PDF file. Print this file in 100% ratio to get 1:1 dimensions. The best way is to go with DWG True View, which is a free to download DWG file viewer from Autodesk.
I’m doing printed circuits boards the photo-chemical way (nice step-by-step in Czech language). Instead of UV lamp I’m using the straight sun light. There are other ways of doing PCB, for example ironing. English step-by-step for making PCB the ironing way. Figure 1 shows my PCB ready for drilling.
Mounting the Digi Connect ME
After drilling the holes with modelers drilling-machine, everything is ready for soldering. It’s good to put some tin around the holes before start, that will help with faster soldering. It’s generally not good when soldering takes too long, because it may cause damage to Digi unit.
The long pins I’ve made from ASS11020G breaking pins, by removing one row of plastic sleeve. I like this solutions very much, because the upper port of the pin, can be accessed by volt-metter stylus.
When soldering is done, PCB is washed with acetone. It will melt the resin from soldering and creates protecting layer on the PCB. On figure 2 and 3 it’s visible how the acetone accidentally washed out the ink from product label.
Figure 2: Digi Connect ME adaptor board ready to go
Figure 3: Beatlle’s belly
Figure 4: Adaptor board pin-out - above view
Bringing it to life
Since the Digi Connect ME is “complete computer” there is no special circuit necessary. There are just +3.3V power suply and ground. The pull-up resistor is needed for /INIT pin which is used for soft-reset. When the pin is grounded, soft reset signal is set. To pull this pin high is not mandatory, for details check the hardware reference manual.
Figure 5: Basic circuit for Digi Connect ME
After connecting to power supply and ethernet, the Digi Connect ME should obtain IP address from network DHCP and be ready for communication. Amber led indicates network connection and green led blinking with network activity. Exact procedure to setting up module with MFdeploy.exe is described in Getting started guide: Digi JumpStart for .NET Micro Framework. When problems occurs, there is a way to setup Digi module over the serial port. In my module, the network connectivity worked well. I can ping the device with MFDeploy.exe and read the device informations.
I still have a problem with deploying application into the module. It’s probably caused by older firmware in my module. I have to do some more research around it and I will publish results soon.
Figure 6: Still-life with Digi Connect ME and breadboard