Over the past weeks we have built a few OpenMote-CC2538 boards and we already have them in our hands. Now we are in the process of testing everything to make sure that it works just as expected. So far, the results look promising! Here is a picture of the board.
In addition to the picture, the main hardware that is included in an OpenMote-CC2538 is the following:
- 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.
- Chip antenna: The board includes the 2450AT18B100E chip antenna from Johanson Technologies. The antenna has an almost omni-directional radiation pattern with an average gain of 0 dBi. You can check the specification in the datasheet.
- Antenna connector: The antenna connector (optional) enables to connect an external antenna to the board. The antennas can be selected using the AS179-92LF RF switch from Skyworks Solutions. 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 USB from Sparkfun.
You may now be wondering how to program and debug your code in the OpenMote-CC2538. Well, in addition to the OpenMote-CC2538 itself we also have something called OpenBase. The OpenBase is used to program the OpenMote-CC2538 using a standard ARM JTAG connector (10-pin) and also interface it with a computer through both UART and USB. We will present further information on the OpenBase in the following post, so stay tuned!