Dexter Serial Peripherals - HaddingtonDynamics/Dexter GitHub Wiki
In most cases, you will control Dexter and other robots, or peripheral including serial devices from DDE on a PC. That allows you to bring the power of the PC and the DDE IDE to bear on the overall control problem. However, in some cases you might want to connect something directly to Dexter and run a job via the Job Engine, which is DDE running on Dexter vs DDE running on the PC.
Serial devices, such as TTL serial adapters, ModBus adapters, or other devices with a serial interface like the OpenMV camera can be connected to Dexter's USB A connector, found just under the CAT5 connector on the MicroZed board.
To verify the connection, you will need to SSH in or connect via the USB console cable.
Once you are at the command prompt on Dexter, with the device disconnected type the following commands (bolded in the sample session below):
ls /dev/co*
/dev/console
ls /dev/tty*
Now, plug in the device and wait a few moments, then enter those same commands again. In this case, I've plugged in a simple USB - TTL adapter based on the CP2102 chip. Look for the difference:
ls /dev/co*
/dev/console
ls /dev/ttyUSB*
/dev/ttyUSB0
As you can see, the new device is there at /dev/ttyUSB0.
Arduino Unos may show up as /dev/ttyACM0.
The OpenMV camera will also show up as /dev/ttyACM# Note: To find and mount the flash drive to program the OpenMV cam, you can use blkid to show available block devices without the device connected, then connect it and use the command again. The new device is the camera. It will probably appear as /dev/sda1: SEC_TYPE="msdos" UUID="4621-0000" TYPE="vfat". To access the contents, make a folder: mkdir /mnt/openmvcam then mount the device: sudo mount /dev/sda1 /mnt/openmvcam/ and the files will appear at /mnt/openmvcam. Edit main.py to change the cameras code. When finished, be sure to umount /mnt/openmvcam
To test it's operation, you can even use the command line to send and receive data. e.g. Here is a sample session for an Arduino device programmed to respond with some binary data and a few analog port readings in response to a "?". You can find the code for that here: https://gist.github.com/JamesNewton/8b994528ff3ce69e60bbb67c40954cd2
stty -echo -F /dev/ttyUSB0 ospeed 57600 ispeed 57600 raw
echo -ne '?' > /dev/ttyUSB0
cat -v < /dev/ttyUSB0
In that session, the following showed up at the console:
<10000000000000,470,419,423,389,362,343>^M
which is exactly what the device was programmed to return.
Note that the -v after the cat causes control characters from the device to be displayed. For example, the carriage return is shown as ^M and the end of the returned string. You can omit the -v if you don't want to see those.
The -echo in the setup of the port turns off automatic echoing of all recieved characters. If you omit this, you may find that the device also receives the data that it sends to you.
(Note, if you are working on a Linux PC, where you do not have root permissions, you may need to:
sudo usermod -a -G dialout $USER
in order to become part of the dialout group, which is required for access to tty devices. )
You can have a two way conversation via typing in data and seeing the result via:
stty -echo -F /dev/ttyUSB0 ospeed 57600 ispeed 57600 raw
cat -v < /dev/ttyUSB0 & cat > /dev/ttyUSB0
Press Ctrl+C to exit the cat from the console to the device, then enter fg 1 and Ctrl+C to exit the cat from the device to the console, which is running in the background, because of the &. jobs should not show anything running.
Next, we want to use the "serial" functions in the "job engine"; DDE on Dexter) but there have been issues which require a little hacking depending on the version you have:
https://github.com/HaddingtonDynamics/Dexter/issues/60#issuecomment-605376411