amt21_driver_cpp

amt21_driver_cpp is a UART to RS485 driver for CUI Devices' AMT21 absolute rotary encoders.

Build and Install

Note: The library will, by default, be installed at /usr instead of /usr/local in order to be plug and play with ROS2

cd amt21_driver_cpp
mkdir build
cd build
cmake ..
make
sudo make install

Usage

Simply find and link the package amt21_driver in the CMakelists.txt

find_package(amt21_driver REQUIRED)

target_link_libraries(mylib/myxecutable amt21_driver)

Giving the UART to RS485 read and write access

Do not forget to give the necessary access to the UART port: sudo chmod /dev/<device>. This change will not be persistent through reboot or device connection/reconnection. To make it persistent, creat an udev-rule. This will require the vendor and product id of the device. Use lsusb in order to determine the <vendorid> and <productid>.

echo 'SUBSYSTEM=="tty", ATTR{idVendor}=="<vendorid>", ATTR{idProduct}=="<productid>", MODE="0666"' | sudo tee /etc/udev/rules.d/99-amt-serial.rules

Then, in order to reload udev-rules run the following commands, or simply reboot.

sudo udevadm control --reload-rules && sudo udevadm trigger

Example udev-rule

In the example a USB to RS485 adapter using the FT232 Serial IC is used.

In a terminal window, lsusb returns the following.

Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 008: ID 0bda:c811 Realtek Semiconductor Corp. 802.11ac NIC
Bus 001 Device 007: ID 05e3:0743 Genesys Logic, Inc. SDXC and microSDXC CardReader
Bus 001 Device 005: ID 05e3:0610 Genesys Logic, Inc. Hub
Bus 001 Device 004: ID 046d:c52b Logitech, Inc. Unifying Receiver
Bus 001 Device 003: ID 31b2:0011 DCMT Technology USB Condenser Microphone
Bus 001 Device 002: ID 1b1c:1b3c Corsair Corsair Gaming HARPOON RGB Mouse
Bus 001 Device 006: ID 0b05:1939 ASUSTek Computer, Inc. AURA LED Controller
Bus 001 Device 009: ID 0403:6001 Future Technology Devices International, Ltd FT232 Serial (UART) IC
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

From the above information it can be determined that <vendorid> = 0403 and <productid> = 6001. Thus, the following udev-rule is applied:

echo 'SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001" MODE="0666"' | sudo tee /etc/udev/rules.d/99-amt-serial.rules

If you share your linux system with other users, or just don't like the idea of write permission for everybody, you can replace MODE:="0666" with OWNER:="<yourusername>" to create the device owned by you, or with GROUP:="<somegroupname>" and mange access using standard unix groups.