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Better Debugging of Embedded via a Debug Port

Better Debugging of Embedded via a Debug Port. ECE152. Overview. Why have a Debug Port? What is a UART? How does the Wunderboard UART work? #DEFINE. What is a Debug Port?. JTAG Digital Satellite, Later ECE courses I2C Proprietary AVR serial ISP Serial (UART).

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Better Debugging of Embedded via a Debug Port

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  1. Better Debugging of Embedded via a Debug Port ECE152

  2. Overview • Why have a Debug Port? • What is a UART? • How does the Wunderboard UART work? • #DEFINE

  3. What is a Debug Port? • JTAG • Digital Satellite, Later ECE courses • I2C • Proprietary • AVR serial ISP • Serial (UART)

  4. Understanding Asynchronous Serial (UART) • Agreed on message format • Start and Stop Bits • Parity • Agreed on speed

  5. AVR Hardware UART Peripheral

  6. Handlinga UART in software • Important Registers • USART I/O Data Register n– UDRn • USART Control and Status Register n A – UCSRnA • USART Control and Status Register n B – UCSRnB • USART Control and Status Register n C – UCSRnC • USART Baud Rate Registers – UBRRnL and UBRRnH

  7. Baud Rate • Speed of transmission • Units of bits per second (bps or baud)

  8. Start and Stop Bits • 1 start bit, 1 or 2 stop bitsUSBSn bit in UCSRnC

  9. FTDI UART to USB chip • Modern computers do not have RS232 • USB to UART converters maintain a simple interface • FTDI Chip works on Windows, Mac and Linux • Often driverless installation • Can be disabled to allow for Wunderboard to Wunderboard serial communication

  10. Voltages • Wunderboard • 3.3V • FTDI • 3.3 to 5V • Old School RS232 • ±12V

  11. Enabling and disabling Debug ports • Why Enable and Disable Debug? • Code Size • Code Speed • Security

  12. #ifdef and Preprocessor Statements • Preprocessor statements happen BEFORE compilation #define DEBUG#ifdefDEBUG Serial code goes here...#endif

  13. Things to Remember • Watch your flags to avoid buffer over run • Use #define to remove code before compilation

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