Reprint: Pixhawk Source note three: Serial interface UART and console

Turn from: Sina @walkant

Part Four serial interface UART and console

Detailed reference: http://dev.ardupilot.com/wiki/learning-ardupilot-uarts-and-the-console/

UART is very important for debugging output, digital transmission, GPS module and so on.

1, 5 UART

A total of 5 UART are defined, and their uses are:

• The uarta– serial terminal, usually a micro USB interface, runs the Mavlink protocol.
• UARTB–GPS1 module.
• uartc– the main number of interfaces, that is, Pixhawk telem1 interface.
• uartd– frequency interface, that is, TELEM2 interface.
• UARTE–GPS2 module.

Some UART have a dual role, for example, by modifying the serial2_protocol parameter, you can change the UARTD mavlink telemetry number to FRSky telemetry digital transmission (Jiangsu, China).

Test the example sketch in the Libraries/ap_hal/examples/uart_test directory and output a hello message for each of the 5 UART. Using the USB to serial port tool, you can test.

2. Debug the Terminal Debug console

As a supplement to the 5 UART, some platforms also have an additional debug console debug terminal. You can judge by examining the Hal_os_posix_io macro definition, such as:

#if Hal_os_posix_io

::p rintf ("Hello console\n");

#endif

If you have defined hal_os_posix_io, you can try to view the Ap_hal/ap_hal_boards.h code.

3. UART function

Each UART has a series of basic operating functions, mainly:

1. printf–formatted Print

2. printf_p–formatted print with Progmem string (saves memory on AVR boards)

3. Println–print and line feed

4. Write–write a bunch of bytes

5. Read–read some bytes

6. Available–check if any bytes is waiting

7. Txspace–check How much outgoing buffer space is available

8. Get_flow_control–check if the UART has flow control capabilities

You can view their definitions in Ap_hal and test them with uart_test.

4. UART Interface Description

Many UART interface, many names, their correspondence, I summarize the following, if there is a problem, please email to [email protected] Sina @walkant, welcome correction.

Code Definition	PCB Circuit Representation	Flight Control Board Interface	Serial Marking	Description
The description in APM code	Representation on a circuit board	Identification on the Pixhawk housing	Serial number
Uarta	Micro USB	Usb	Usb	USB connection, Support Mavlink protocol
Uartb	UART4	Gps	Serial 3	Connect the GPS module to the other CAN2 interface
Uartc	UART2	Telem1	Serial 1	Connect the 1th Digital transmission module
Uartd	UART3	Telem2	Serial 2	Connect the 2nd Digital transmission module
Uarte	UART8	Serial4/5	Serial 4	General Connection GPS2 Module
/	UART7	Serial4/5	Serial 5	Debug Console for program debugging

Previous article:

Pixhawk Source Note One: APM code basic structure: http://blog.sina.com.cn/s/blog_402c071e0102v59r.html

Pixhawk Source Note two: APM Thread: http://blog.sina.com.cn/s/blog_402c071e0102v5br.html

The UART Test code: LIBRARIES/AP_HAL/EXAMPLES/UART_TEST) is tested in detail:

void loop (void)
{

Micro USB port output : Hello on UART uarta at 764.461 seconds
Test_uart (Hal.uarta, "Uarta");

GPS Interface Output :Hello on UART uartb at 91.845 seconds
Test_uart (HAL.UARTB, "UARTB");

Digital Telem1 output :Hello on UART uartc at 24.693 seconds
Test_uart (HAL.UARTC, "UARTC");

Digital Telem2 output :Hello on UART uartd at 805.557 seconds
Test_uart (HAL.UARTD, "UARTD");

seiral 4 Port output :Hello on UART uarte at 911.812 seconds
Test_uart (Hal.uarte, "Uarte");

Also do-a raw printf () on some platforms, which prints to the
Debug console
#if Hal_os_posix_io

seiral 5 Port output: Hello on debug console at 976.857 seconds
::p rintf ("Hello on debug console at%.3f seconds\n", Hal.scheduler->millis () *0.001f);
#endif

Hal.scheduler->delay (1000);
}

SERIAL 5 As an important debug port. A large amount of information is output through this interface when the Pixhawk is started and can be used to monitor the boot process.

Reprint: Pixhawk Source note three: Serial interface UART and console