Networking (with PSoC)

For the assignment of networking we decided to implement serial communication between two microcontrollers from the PSoC family that we have been using. The intention was to be able to read the distance from the sensor on a remote microcontroller.

The set-up was straight forward. A new block was added: UART (universal asynchronous receiver transmitter) which enables the serial communication. As with previous assignments, the block can be connected to the desired pins for input (RX) and output (TX). Additional parameters specific to the UART were set in the configuration of the UART such as the speed (System Clock / 256), a token for message termination (in this case set to character '+' which is ascii 43 specified in "Command Terminator"), and buffer size among others.

 

 

 

Once the set-up was done, the changes in the code were really simple, consisting of initializing the UART, sending out the string and clearing out the flags after the transmission. Two alternatives were tested, sending out strings and sending out integer values which in this case corresponds to the read from the analog input 'ADCData'. The remaining of the code did not change and can be seen in the output devices homework.

 

 

For the remote controller a commercial development board of PSoC was used mainly due to availability. This development board is just a platform with access to all the ports of the microcontroller, a small breadboard and an LCD, similar to both boards developed in house that were used for the previous assignments and the master. The connection between both systems was done through 2 wires TX and RX from the master that went into RX and TX of the remote respectively. The setup was similar to the one described above including the UART block and configuring the appropiate speed, token for termination and buffer size. 

 

 

The code was fairly simple although it require a lot of time to understand some of the details of the microcontroller for a successful implementation. As mentioned above two strategies were tested with similar results, receiving strings and integer values. The code necessary for integer values is commented. For the strings the code consisted in waiting for the termination token to be detected using "UART_1_bCmdCheck()", then grabbing the string in the buffer with a pointer and then displaying the string in the LCD. The flag for the termination token was reset and the process started all over again.

 

 

 

Although the code was simple and the message that was being transmitted was simple, the first few trials showed that there was something wrong with the communication since data was received but it did not correspond to the distance being read at the master. Sometimes it was totally off, and sometimes it was close like in the individual figures below.

 

 

After a few trials and some debugging it became clear that there was noise in the transmission line and that having a common ground for both boards may eliminate the problem. Indeed having a common ground helped and both boards showed the appropriate values consistently.

 

 

 

 

Finally the boards were set to work without any connection to the computer (before the programmer was supplying power to the remote board) responding as expected.