CASP supports exchanging data simultaneously between one or more micro-controllers and host computer with very low latency. Data received from the micro-controllers can then be analyzed with the help of CASP GUI widgets such as plotters, dials, 2D/3D graphs.
This example project demonstrates a model that establishes RS485 communication between two target boards and the host (native) PC. We try to acquire analog data from the target boards to the host PC through RS485 communication and plot the data on the host PC. We also try to control the on-board LED present the target boards from the host PC.
Pre-Requisites
- Arduino Uno R3 and Arduino Nano is used for this example. However, any CASP supported micro-controller boards can be used.
- USB to RS485 Converter Module
- RS485 to TTL Converter Modules
- Compatible USB cables.
- CASP software is installed along with CASP Python Libraries.
- Arduino BSP is installed.
- The project files are located at CASP installed directory ‘CASP/support/examples/communication/2_rs485’. These are also available for download at this link.
Description
Analog data is acquired from the target boards on the host PC through RS485 communication and the acquired data is plotted on the host PC. We also try to control the on-board LED present the target boards from the host PC.
CASP Model for Arduino
Procedure
- Connect any sensor to the ADC pin A0 of Arduino Uno and Arduino Nano for sensing. We use the on-board LED at pin-13 for controlling. Connect the two boards along with they respective RS485 converter modules to the host PC as shown in the connection diagram above. A resistor of value between 120 to 220 Ohms shall be connected between RS485 communication wires (A & B).
- Connect Arduino Uno to the host PC via a USB cable.
- Note the serial port number to which the board is connected to the host PC, from the host operating system.
- Run CASP and open the project ‘CASP/support/examples/communication/2_rs485/target_model/target_model.prj’ from CASP installed directory.
- Ensure that the Slave Device Index parameter of the Serial block is assigned properly as mentioned in the model.
- Open Home->Simulation->Setup Simulation Parameters menu item. Under TargetHW->General tabs set ‘Target Programmer Port’ parameter to the serial port to which the board is connected.
- Build the model and program the board by clicking on Run button.
- Repeat the above steps to program Arduino Nano board.
CASP Model that runs on Host Computer
Procedure
- Run CASP and open the project ‘CASP/support/examples/communication/2_rs485/native_model/native_model.prj’ from CASP installed directory.
- With the USB to RS485 module connected to the host PC, click on Home->Simulation->Configure Simulation IO menu item.
- ‘Configure Simulation Hardware’ window will open. Change the serial port marked in the below figure (by double clicking on the item) to the port where USB to RS485 module is connected.
- Click on ‘Connect Device’ button and check the ‘Online Data’ check box. The program should now communicate with the two targets with cycle time around 10msecs. If cycle time is more than this value then configure USB to RS485 module serial port latency settings to the minimum value. Target boards are now available as end points EP0 and EP1 to the native model. Native model can use these end points to connect to respective IOs on the targets.
- Click on ‘Save’ button to save the configuration and close the window.
- Run the model by clicking on the Run button. A simulation panel window should open and communicate with the two boards. A screen shot is shown below. From the simulation panel toggle the two switches to control the on-board LEDs of the two targets
