8.5. Consoles

The RTEMS Tester uses the target’s console output to determine the state of a test. Console interfaces vary depending on the testing mode, the BSP, and the target hardware.

Consoles for simulator work best if mapped to the simulator’s stdout interface. The RTEMS Tester can capture and process the stdout data from a simulator while it is running.

Target hardware console interfaces can vary. The most universal and stable interface target hardware is a UART interface. There are a number of physical interfaces for UART data these days. They are:

  1. RS232
  2. TTL
  3. USB

RS232 is still present on a number of targets. The best solution is to use a RS232 to USB pod and convert the port to USB.

TTL is common on a number of boards where cost is important. A console interface is typically a development tool and removing the extra devices need to convert the signal to RS232 or directly to USB is not needed on production builds of the target. There is a standard header pin out for TTL UART consoles and you can purchase low cost cables with the header and a built in UART to USB converter. The cables come is different voltage levels so make sure you check and use the correct voltage level.

The USB interface on a target is typcially a slave or OTG interface and all you need to a standard USB cable.

We recommend a low cost and low power device to be a terminal server. A Raspberry Pi or similar low cost computer running Linux can be set up quickly and with a powered USB hub and can support a number of USB UART ports. A USB hub with a high power port is recommended that can suppy the Raspberry Pi.

The open source daemon ser2net is easy to configure to map the USB UART ports to the Telnet protocol. There is no need for security because a typical test environment is part of a lab network that should be partitioned off from an enginnering or corportate network and not directly connected to the internet.

A test set up like this lets you place a terminal server close to your target hardware providing you with the flexibility to select where you run the RTEMS Tester. It could be your desktop or an expensive fast host machine in a server rack. None of this equipment needs to directly interface to the target hardware.

The RTEMS Tester directly supports the telnet protcol as a console and can interface to the ser1net server. The telnet console will poll the server waiting for the remote port to connect. If the terminal server ser2net does not have a tty device it will not listen on the port assigned to that tty. A USB tty can come and go depending on the power state of the hardware and the target hardware’s design and this can cause timing issues if the target hardware is power cycled as part of a reset process.