Electric Imp Developer Wiki
Designing a new impee device is relatively straight forward. Your design must meet the minimum design requirements. You will need to decide whether the impee will require an imp or be augmented by an imp. You will also need to consider your power topology and select the functionality you need with the pin mux. During layout, you will need to follow the recommended layout and routing guidelines. When you have built your device, you will need to bind it to a firmware and start developing code for your impee. If you are going to mass produce your impee, you will need to learn how to provision each new impee as it is born.
Every impee must have a compatible socket, power supply and ID chip.
imp's are compatible with most SD Card sockets, but we recommend the 4ucon 19608. Avoid sockets which have metal near the open side as these may interfere with the antenna.
An alternate which is easily available from distributors is the Amphenol 101-00313-68-02. You can find this at Digikey.
Dirk Verhaegen has kindly provided an Eagle footprint for the Amphenol socket, see here.
The imp runs from a 3.3V DC power supply capable of providing 400mA. It may be possible to run an imp from lower voltages, please contact us for more details.
Each impee must have an Atmel ATSHA204 chip connected to pin 6 and pulled up to the imp power rail with a 100kΩ resistor. Each ATSHA204 has a unique ID which is used to identify your impee.
impees may either be Imp Ready or Imp Powered devices. Imp Ready devices must function on their own without the presence of an imp. For example a bathroom scale could be Imp Ready, it would measure and display your weight without an imp. Imp Powered devices have little or no functional behavior when the imp is removed. For example a temperature monitor with an I2C temperature sensor may not need any processor other than the imp so when the imp is removed it has no function. In Imp Powered devices, every effort should be made to ensure the impee behaves in an expected and safe way.
The imp requires a 400mA, 3.3V power supply. While the majority of the time, it will operate at substantially lower power levels, there are times, such as during firmware updates, where it may need to run at this level for several seconds.
For descriptions of pin of function see the Imp Pin Mux.
Summary is no copper should be present on the PCB, on any layer, for the full width of the socket beyond the front two mounting pads. Please see the example designs and gerbers for examples of this, and please email us if you require any further clarification.