The OpenMote-CC2538, depicted in the following image, is the core of the OpenMote hardware. If connected to theOpenBattery board it can interface various sensors and operate autonomously as a node. If connected to theOpenBase board it can interface other networks and operate as a gateway. Currently the OpenMote-CC2538 is already supported by Contiki, OpenWSN and FreeRTOS, as described in the Software section.
The OpenMote-CC2538 includes the following hardware:
- CC2538: It is a SoC (System on Chip) from Texas Instruments with a 32-bit Cortex-M3 microcontroller and a CC2520-like radio transceiver. The microcontroller runs up to 32 MHz and includes 32 Kbytes of RAM and 512 Kbytes of Flash, as well as the usual peripherals (GPIOs, ADC, Timers, etc.). The radio operates at the 2.4 GHz band and is fully compatible with the IEEE 802.15.4-2006 standard. You can check the specifications in the datasheet.
- TPS62730: It is a step-down DC/DC converter from Texas Instruments with two operation modes, regulated and bypass. In bypass mode the TPS62730 directly connects the input voltage from the battery (typically 3 V) to the whole system. In regulated mode the TPS62730 regulates the input voltage (typically 3 V) down to 2.1 V. The benefit of such approach is that the whole efficiency of the system can be improved under both low and high load conditions, that is, either when the system is sleeping or when the radio is transmitting or receiving. You can check the specifications in the datasheet.
- ABM8G: It is a 32 MHz crystal from Abracon Corporation used to clock the microcontroller and the radio transceiver. The part is rated at 30ppm (parts per million) from -20 ºC to +70 ºC. You can check the specifications in the datasheet.
- ABS07: It is a 32.768 kHz crystal from Abracon Corporation used to clock the microcontroller RTC (Real Time Clock). The part is rated at 10ppm (parts per millon) from -40 ºC to +85 ºC. You can check the specifications in the datasheet.
- LEDs: It includes 4 LEDs (colors: red, green, yellow and orange) from Rohm Semiconductor for debugging purposes. You can check the specifications in the datasheet.
- Buttons: It includes 2 buttons from Omron, one is used to reset the board and the other is connected to a GPIO line, thus enabling to wake up the microcontroller from sleep modes through an interrupt. You can check the specifications in the datasheet.
- Antenna connector: The antenna connector enables to connect an external antenna to the board. You can check the specification in the datasheet.
- XBee layout: The OpenMote is fully compliant with the XBee form factor, meaning that it can be easily interfaced with a computer using the XBee Explorer Dongle from Sparkfun (attention, it is not physically compatible with the XBee Explorer USB due to JTAG/USB pins interfering with the USB connector).
Here you can download the OpenMote-CC2538 Schematic.