The LabNation SmartScope is an extremely versatile digital storage oscilloscope that transforms your smartphone or tablet into a full-featured DSO. This unit features a powerful set of protocol decoders usually only found on pricey mixed-signal oscilloscopes or logic analyzers. An example of the usefulness of this feature will be presented in the real-world application of a wireless communication link using the RS232 asynchronous serial bus.
A system for a remote paging was designed using the RF modules from Circuit Specialists. The STPA-418 transmitter and RXB4411S-418-RH receiver were chosen due to their low cost and simplicity of use. An asynchronous serial protocol is required for communicating data over an RF link and is easily created with the UART of any microcontroller such as an Arduino-compatible board or PIC.
Since we live in a wireless age, we are continually bombarded by myriad RF signals from cell phones, WiFi networks, and radio communication systems. These RF signals can create false signals on our paging system, so our circuitry must be able to differentiate between valid and invalid data. This is where a protocol decoder was found to be invaluable as we can see at a glance the decoded value of the data received.
If a protocol decoder is not available, we must count rising edges and write down logic 1s and 0s, which must then be manually converted into the corresponding hex value of the data. The protocol decoder automates this entire process and even translates this value into humanly readable words specific to your application code. This feature is unique to the SmartScope among the various oscilloscopes and logic analyzers available from Circuit Specialists.
The example shown illustrates the usefulness of the unit in tracking down garbled data caused by RF interference in the environment. To ensure that the received data was valid, a series of start bytes are transmitted, which are used to synchronize the receiver and set up the automatic level control (ALC) circuitry of the receiver. Next, a preamble consisting of a series of digital words of a known value is sent. The digital words are used to differentiate valid data and random noise. Finally, the actual data is sent and repeated several times as a final error checking method.
As can be seen from the attached screen shots, the first received byte was garbled and therefore not correctly validated. Many hours were wasted trying to determine the reason that our system was missing data. Once the protocol decoder was implemented, it was only a matter of minutes to see the incorrect data in the received data stream.
The LabNation SmartScope is a compact yet powerful digital storage oscilloscope that transforms your smartphone or tablet into a powerful debugging tool. The built-in protocol decoders are invaluable when troubleshooting modern data communications.