ATSAMA5D27-SOM1-EK1 - Console Serial Communications
Introduction
In this topic, you will learn how to connect a host computer running a terminal emulation program to the ATSAMA5D27-SOM1-EK1 evaluation kit J-Link Communication Device Class (CDC) serial port to access the Console.
The Console (also known as DEBUG, Device Console, Target Console, Applet Console, or simply Console) is a serial communications port (generally a Universal Asynchronous Receiver Transmitter (UART)) on the target device (thus the term Target Console or Device Console) that communicates with a terminal emulation program on a host computer. It provides status information from an operating system, such as the Linux® boot log, and debug information from utility programs, for example, from SAM-BA® Applets.
Prerequisites
Familiarity with the features of the ATSAMA5D27-SOM1-EK1 evaluation kit.
J-Link CDC Serial Port
The J-Link CDC serial port (J10) of the ATSAMA5D27-SOM1-EK1 evaluation kit provides a debugging interface using a SEGGER J-Link-Onboard debugger. Microcontroller U4 and support circuitry provide a JTAG interface to the debugger.
When the J-Link debugger is not in use, microcontroller U4 provides USB CDC serial communications between the ATSAMA5D27-SOM1 UART and micro-B USB connector J10.
When the host computer is connected to the J10 of the evaluation kit, the ATSAMA5D27-SOM1-EK1 will enumerate as a CDC. A terminal emulation program running on a host computer provides a user interface to interact with the target console.
Terminal Emulation Program
Download, install, and configure a terminal emulation program onto your host computer. There are several choices for terminal programs. Below is a list of popular programs. Many are free to download and a few are included with the operating system or distributions.
Windows®
To locate the COM port, open the Windows Device Manager and expand Ports (COM & LPT). Look for JLink CDC UART Port and note the COM port number. You will use this to configure the terminal emulator. You will also need to set:
- Baud: 115200
- Data Bits: 8
- Parity: None
- Stop Bits: 1
macOS®
- Screen
- Find the serial port: $ ls /dev/tty.*
- To run: $ screen /dev/tty.usbmodemFD121 115200
- To quit: $ Control-a $ Control-\
- Minicom
- Perform an Internet search: “minicom for macOS”
- Serial
- Available from the Apple App Store
- CoolTerm
To locate the serial port, you can open the CoolTerm application and note the available ports that are available in the Port selection. You will also need to set:
- Baud: 115200
- Data Bits: 8
- Parity: None
- Stop Bits: 1
Linux
- Minicom
- PuTTY
You can install minicom and putty from the command line. $ sudo apt-get install putty
You will need to set:
- Baud: 115200
- Data Bits: 8
- Parity: None
- Stop Bits: 1
To find the USB port, execute dmesg on the command line:
usb 3-1: New USB device found, idVendor=1366, idProduct=0105
usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-1: Product: J-Link
usb 3-1: Manufacturer: SEGGER
usb 3-1: SerialNumber: 000483029459
cdc_acm 3-1:1.0: ttyACM0: USB ACM device
usbcore: registered new interface driver cdc_acm
cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters
Note the USB port with the Product ID of J-Link. The device will be enumerated as a USB ACM device.
Connecting Host to Target
Connect the host PC to the J-Link CDC serial port (J10) using a USB Micro-B connector. The host PC will enumerate as a CDC.
If there is no SD Memory Card installed, the J-Link Onboard LED will flash green and the RGB LED will flash red.
On the terminal emulation screen, you will see RomBOOT indicating the first-stage bootloader did not find an image to execute, and the SAM-BA Monitor is running and awaiting a command.
Booting a Linux Image
The J-Link CDC serial port is used as the Linux Console when booting a Linux image. For more information, see the following topics:
SAM-BA In-System Programmer
The J-Link CDC serial port is used as an Applet Console to the SAM-BA In-System Programmer.
Summary
The J-Link CDC serial port is a communications port to the target device UART which has been configured as the Console by the Boot Configuration Word. The serial port communicates with a host computer running a terminal emulation program. The Console provides status information from operating systems, such as Linux, and debug information from utility programs (for example, from SAM-BA Applets).
