Introduction
Troubleshooting low-speed serial data buses can be quite challenging. Fortunately, capturing and decoding messages is a strength across Teledyne LeCroy’s oscilloscope product line. In some cases, an engineer may want to capture a particular frame and retransmit it. This is made possible using Teledyne LeCroy’s WaveStation waveform generator.
The WaveStation waveform generator uses WaveStation PC software, which may be downloaded free from Teledyne LeCroy’s website. This software imports waveforms directly from Teledyne LeCroy’s WaveAce series oscilloscopes (see “WaveAce Integration with WaveStation”). However, one may also use the WaveStation PC software to transmit waveforms captured and saved in Excel or ASCII format from other sources. The following procedure illustrates this capability by capturing a UART frame, formatting it to be compatible with the WaveStation PC software, and sending it to the WaveStation waveform generator for further application.
Procedure
First, capture a UART frame and save it to Excel or ASCII format. The UART frame shown in Figure 1 was acquired with a timebase setting of 500 µs/div (total acquisition time of 5 ms), and a maximum memory setting of 10 kS (displayed on a Teledyne LeCroy oscilloscope). This means the waveform is 5 ms long, and comprises about 10,000 points. This waveform is saved in Excel Format. The values taken from this file are amplitude only, although any sub-format could be used.
Next, open the WaveStation PC software and select File > New. The number of samples is set to 16 ksamples (sampling may be set to 16 ksamples or 512 ksamples when using Channel 2 of WaveStation 3000 models). In this case, because the acquired waveform has 10 ksamples, 16 ksamples is chosen. The period is set to 8.191 ms. This period setting is chosen to scale the time values in the new waveform file to that of the acquired UART waveform. The acquired UART waveform has exactly 10,002 samples. The WaveStation waveform has exactly 16,384 samples.
UART frame displayed on a Teledyne LeCroy oscilloscope
The acquired UART waveform total acquisition time is 5 ms.
0.6104x = 5ms
The scaled total acquisition time for WaveStation waveform file is 8.191ms, where 8.191 ms = 5 ms/0.6104
Click Ok, and then Save the new waveform by clicking File > Save and selecting a path. After saving, close the waveform file in the WaveStation PC software.
Open the acquired UART waveform in Excel, select all 10,002 amplitude values, and Copy.
Paste the 10,002 amplitude values into the value column of the Wavestation waveform file.
The remaining amplitude values of samples 10,003 to 16,384 are set to 5 (UART idle state is high; if idle state was low, the remaining samples could remain at 0). Select File > Save, and save the file in .CSV format. Close Excel.
Open the WaveStation PC software, and select File > Open. Navigate to the edited WaveStation waveform file and open it.
Click the Send Wave button at the bottom of the WaveStation software’s interface. In the Send Wave Dialog box, click Send.
On the WaveStation, ensure that the signal sent to the instrument is highlighted (it should be by default) and touch Done (touch Select on WaveStation 2000 models).
The signal from the WaveStation is now loaded. On the Wavestation, select the appropriate output to begin generating the waveform.
The Wavestation is now transmitting the UART frame (shown below in Figure 8). The UART frame is being captured on a Teledyne LeCroy oscilloscope using the oscilloscope’s serial trigger, and decoded.
Conclusion
The WaveStation waveform generator is a highly capable and versatile tool that can be used to generate a multitude of waveforms. When WaveStation is used with the WaveStation PC software, low-speed serial data frames can be captured, modified, and re-transmitted. This capability aids engineers in troubleshooting low-speed serial data communications.
