Oscilloscope Serial Data Measurements and DAC: Trigger, Decode, Measure/Graph and Eye Diagram Software

Figure 1. Serial bus measurements made available
with "TDME" and "TDMP "decoder options.

All Teledyne LeCroy oscilloscopes support a rich set of standard waveform measurement parameters, but the installation of any "TDME" or "TDMP" serial decoder software option adds special parameters designed for measuring serial data buses. Besides automating the measurement of serial bus timing, these parameters allow you to access encoded serial data and extract it to analog values for what is essentially a Digital-to-Analog Converter (DAC)!

What’s in a Name?

Teledyne LeCroy has adopted the convention of using a key in the name of our serial trigger and decode products that tells you what capabilities they offer.  The “ME” or “MP” in the name of a Teledyne LeCroy serial decoder option (e.g., CAN FDbus TDME or USB4-SB TDMP) refers to "Measure/Graph and Eye Diagram" or "Measure/Graph and Physical Layer Tests." All these options include the following 10 serial bus measurements. Physical Layer Test options will also include measurements designed specifically to meet the requirements of the standard.

Correlating Sensor and Serial Data in Complex Embedded Systems

Figure 1: Voltage output of a temperature sensor.
As the temperature rises, the output voltage falls. 

The microcontrollers/microprocessors in deeply embedded systems often are set up to monitor and control operational parameters.  Take, for example, a deeply embedded system where a microcontroller is used to control temperature that has been sensed by a temperature sensor.  The sensor is read through one of the microcontrollers analog interfaces.  As temperature changes are sensed, the microcontroller adjusts the speed of a cooling fan, which is driven by a pulse width modulated signal. The microcontroller uses a program algorithm to convert the DC level of the sensor into a PWM signal with an appropriate duty cycle to set the fan speed to correct any changes in temperature. 

Where it is possible to probe the temperature sensor, the output is a DC signal that changes very slowly over time.  Figure 1 shows a direct measurement of the temperature sensor using a heavily filtered oscilloscope channel to minimize noise pickup.