Analyse Arduino Uno Bootloader with MSO64B

I created a photo montage below showing how to use a mixed signal oscilloscope as a logic analyzer. 

First, I establish a UART bus by connecting the analog probes to the Rx/Tx pins on the Uno board. This setup allows me to monitor the data transfer between the board and the IDE. 

Then, I use the scope’s “data rate” measure option to find the boot loader baud rate 115,200. 

Alternatively the baud rate can be found in boards.txt file.

Extract from {ide}/hardware/Arduino/avr/boards.txt

uno.upload.tool=avrdude
uno.upload.protocol=arduino
uno.upload.maximum_size=32256
uno.upload.maximum_data_size=2048
uno.upload.speed=115200

Then, I set up my scope’s single event trigger options to capture all transferred data – about 2.5 seconds. 

Finally, I use the bus table to navigate the captured waveform and digital data. In this case, at the beginning, where the board and IDE exchange handshake information starts.

The RS-232 decoder bus for Tektronix MSO6 series oscilloscopes can use two analog scope channels. I found this to be a great combination of detail and flexibility

References:

• Arduino (UNO R3 not R4) as ISP (In-circuit Serial Programmer) and Arduino Bootloaders: https://docs.arduino.cc/built-in-examples/arduino-isp/ArduinoISP/
• What happens when code is uploaded using the bootloader? https://arduino.stackexchange.com/questions/15936/
• 6 Series B MSO Mixed Signal Oscilloscope: https://www.tek.com/en/products/oscilloscopes/6-series-mso