On-Board Computer V.1.5
The On-Board Computer (OBC) is based on an STM32F4 AMR cortex microcontroller and at the end of the development process the 1.5 version was sent to production. The OBC organizes the communication between the modules, collects house-keeping and GPS data and also compiles the telemetry packets. System events are logged and can be downloaded from the SD card of the OBC. The House-keeping data is also stored on the SD card.
- STM32F407VGT6 32-bit ARM Cortex-M4F microcontroller, 1 MB Flash, 192 KB RAM
- System Clock: Real Time Clock (RTC)
- UART connection for GPS modul
- CAN controller + CAN transceiver
- DCMI port for integrated camera control
- Micro SD-card slot
- Diagnostic port
- 2×20 pin stackable UPRA-BUS connector
The new On-Board Computer is produced in the UPRA form factor, in the size of 70x75mm (2.76″x2.96″). This is a huge size reduction compare to the previous model.
GPS coordinates, altitude and speed was provided by an NV08C-CSM module. This GPS reciever was designed for high-altitude operations and has an altitude limit of 50 kms (~32 miles), so we could track the entire flight of the balloon. The NV08C module communicates with the OBC through NMEA standard. Parsing the proper NMEA messages longitude, latitude, altitude and speed data could be processed. Each GPS NMEA word has time stamp which used for synchronize the system time. Time Sync is needed, because the Real Time Clock (RTC) unit of the OBC produce increasing slip due to the temperature decrease.
The internal temperature and the stabilized supply voltage was measured by the microcontroller of the communication unit. These data, the exchange between the COM and the OBC during the preparation of the radio communication action.