The STIFF-FLOP hardware integration platform is a universal system for connecting input and output components to a PC running the Robot Operating System (ROS).
The connection is made via EtherCAT which allows for fast, high bandwidth, real time communication between the ROS software components and the attached hardware.
The hardware consists of two basic components:
1. Modules – One or more modules are connected in a chain, and allow the connection of sensors and actuators.
2. Bridge – This connects the chain of modules to the PC.
Since a variety of different modules will be required by the project, the design of the module has been split into two parts: The part which is the same for each module, and the part which can change.
The part which is the same for every module contains the EtherCAT ASIC and PSoC chips. The EtherCAT ASIC handles the physical layer and protocol of EtherCAT. The PSoC exchanges data with the EtherCAT ASIC, and handles all of the I/O. It is a very flexible device, that allows to change its pins from Digital I/O to Analog I/O simply by updating the firmware.
The part which changes is fairly simple, and is known as the Stacker board. It basically only contains the connectors required by the application, as well as the voltage regulators. More sophisticated applications may require extra electronics on the Stacker board; for example higher resolution ADCs, instrumentation amplifiers, high current drivers, etc.
One type of stacker board has been designed and made so far, which contains a mix of functionality: 4 Digital I/Os, 2 Analog outputs, and 4 Analog Inpu
Each chain of modules requires one bridge board to connect it to the PC. Like the modules, the bridge has also been split into two parts. The Bridge Base Board, and the Phy board.
This is to save on cost. Most users will want only one chain of modules, in which case they can use one Base board and one Phy board. If they wish to have more than one chain of modules separated by a long Ethernet cable, then they can add another Phy board to connect the Ethernet cable to. The Bridge base board also contains the power supplies needed to convert the 9v-12v input down to 5v and 3.3v for the electronics.
The boards will all be housed in Aluminium casings. These are available in a range of sizes to suit the needs of the modules, and also in different colours to help identify them. The modules are connected together with standard HDMI cable. These are low cost, easily obtainable, and available in a range of lengths.
We are currently finishing the software and firmware needed to make the system work. We expect to have a demonstration ready by early July.