A logic analyzer lets you verify SPI transactions in real time — seeing the actual waveforms confirms that clock polarity, phase, bit order, and data values are correct. The examples in this repo include channel comments directly in the sketch headers, making it straightforward to wire your analyzer probes to the right pins and configure the decoder without guesswork.Documentation Index
Fetch the complete documentation index at: https://mintlify.com/manish04-mu/TheEmbeddedInsights/llms.txt
Use this file to discover all available pages before exploring further.
Why Use a Logic Analyzer
Verify Mode
Confirm CPOL/CPHA settings by observing the clock idle state and the edge on which data transitions. A single glance at the SCK waveform tells you if your mode is correct.
Decode Data
See the actual hex bytes sent on MOSI and received on MISO, decoded frame by frame. Instantly verify that
0x62 is being transmitted as expected.Debug Timing
Identify CS assertion timing, missing clock pulses, or glitches that cannot be detected from Serial Monitor output alone. Timing issues are visible at a glance.
Validate Bit Order
Confirm MSB-first vs LSB-first transmission by inspecting the individual bit sequence in the captured frame. Switch between
MSBFIRST and LSBFIRST sketches and see the difference immediately.Channel Mapping
Every sketch in the repository includes the following channel assignment comment at the top. Wire your logic analyzer probes accordingly:| Channel | Signal | Arduino UNO Pin | Description |
|---|---|---|---|
| CH0 | SCK | 13 | SPI clock signal |
| CH1 | CS / Enable | 10 | Chip Select — active LOW |
| CH2 | MOSI | 11 | Master Out Slave In (data to slave) |
| CH3 | MISO | 12 | Master In Slave Out (data from slave) |
Decoder Settings
In most logic analyzer software — including Saleae Logic and Sigrok / PulseView — configure the SPI decoder as follows after wiring the probes:- Clock: CH0 (SCK)
- Enable / CS: CH1 — set polarity to active LOW
- MOSI: CH2
- MISO: CH3
- CPOL / CPHA: match the mode used in the sketch (e.g., CPOL = 0, CPHA = 0 for
SPI_MODE0) - Bit order: match the
SPISettingsargument —MSBFIRSTorLSBFIRST - Word / frame length: 8 bits
Sampling Rate
The example sketches use a clock speed of 100 kHz. Logic analyzer best practice requires sampling at least 10× the clock frequency to accurately reconstruct waveform edges. That means a minimum sample rate of 1 MHz; a rate of 4–10 MHz is recommended to cleanly resolve fast edges and avoid aliasing artifacts. Check your analyzer’s specifications and set the sample rate in the capture software before starting a capture session.
Connecting the Probes
Connect CH0 to SCK
Clip the CH0 probe to Arduino pin 13 (SCK). This is the clock line and is always the reference channel for the SPI decoder.
Connect CH1 to CS
Clip the CH1 probe to Arduino pin 10 (CS / Chip Select). The decoder uses a falling edge on this line to detect the start of a transaction.
Connect CH2 to MOSI
Clip the CH2 probe to Arduino pin 11 (MOSI). This carries the data byte sent from the Arduino master to the slave.
Connect CH3 to MISO
Clip the CH3 probe to Arduino pin 12 (MISO). This carries the data byte returned from the slave to the Arduino master.
Connect the ground clip
Connect the logic analyzer’s ground clip to any GND pin on the Arduino. A shared ground reference is essential — without it, signal levels will be meaningless and decoding will fail.