Plug-in Modem Support
The CubeSat Kit accepts a variety of off-the-shelf modems / transceivers. The MHX 425/900/910/920/920A/2400/2420 series of spread-spectrum transceivers from Microhard Corp are directly supported, as well as the 9XStream series of 900MHz transceivers from MaxStream/Digi, via adapters. In order to minimize power consumption, +5V/+3.3V power to the modem is under software control from the PPM.
The CubeSat Kit includes a USB-2.0-compliant USB port. This port can be used to communicate between the CubeSat Kit and any PC or Mac running Windows, Mac OS X or Linux. Custom CubeSat Kit drivers for Windows and Mac OS X are provided.
Additionally, the CubeSat Kit can be powered through the USB port up to a maximum of 500mA. This is useful in situations like pre-launch checkouts, software diagnostics, bootloaders, updates, etc.
Multiple Serial Interfaces
All CubeSat Kit PPMs provide at least two UARTs, one SPI channel and one I2C channel. They are typically utilized as:
- UART0 is free to the user, e.g. to communicate with a payload via an asynchronous serial protocol (e.g., RS-232)
- UART1 is normally dedicated to the transceiver interface.
- SPI0 is typically used in to communicate with the on-board SD/MMC card mass storage device. It can also be used to communicate with other SPI devices, via additional chip select lines
- I2C0 is typically used to communicate with I2C devices (e.g., EPS, onboard RTC, payload, etc.)
Different PPMs have different serial peripheral capabilities. PPM D1 has four UARTs, three SPIs and three I2Cs, which leaves at least two UARTs, two SPIs and two I2Cs completely open for user assignment. On the other hand, PPM A1|A2|A3 shares UART0 and SPI0 across the same on-chip peripheral (the MSP430's USART0), i.e. UART0 and SPI0 cannot be active at the same time.
The Development Board provides an RS-232 driver for UART0 to aid in printf()-style debugging, etc.