Bus Pirate: miniscope v3

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Miniscopev3-example.png

Contents

Requirements

Application is using continuous voltage measurement bitbang mode and requires (at least) version 5.8 of the Bus Pirate firmware.

Sampling parameters

  • Each sample is 10 bit unsigned with 0 V to 6.6 V measurement range.
  • Sampling frequency is 5720 sps.

For a digital oscilloscope, a rule of thumb is that the continuous sampling rate should be five to ten times the highest frequency desired to resolve, so it should be applicable for measuring signals up to 500 - 1000 Hz.

Although data stream is continuous, application is splitting samples into frames (frame length: Buffer parameter) and displaying single frame at once. Larger data collection can be captured and displayed later using recording function.

Setup

  • Edit device\bus_pirate.cfg
  • Set ComPortNumber to your Bus Pirate serial port

Connections

Bus Pirate Dir. Circuit Description
ADC Signal Signal to measure
GND GND Signal Ground
  • Connect the Bus Pirate ADC probe pin to the signal source. The signal can be up to 6volts max
  • Connect the Bus Pirate ground pin to the signal source ground

Use

Miniscope ui usage.png

Modes

  • oscilloscope - basic trace view
  • FFT - amplitude spectrum calculation for current data frame
  • recorder - this mode was intended to capture slowly changing signals over a very long period of time (i.e. GoldCap/SuperCap self-discharge characteristics) by capturing data frame at regular time intervals (10's of seconds), calculating average value and adding only a single point to the plot; this mode name is confusing as there is another recording function writing samples directly to disk file

Plot tools

  • cursors: use left and mouse buttons to set cursor position
  • moving: click on any part of display area and drag to move plot
  • zoom: use left mouse button to zoom in, right mouse button to zoom out; plot is centered at the action coordinates

Additional toolbox is toggled on/off by middle mouse button on display area.

Continuous data recording

Use File/Record data to MS3 file option to initialize continuous recording. Each captured data frame will be written to file with it's parameters and timestamp. If continuous trigger would be selected then frames will create uninterrupted data stream. After opening ms3 file select multiple frames next to each other to combine and load data.

Data exchange

  • CSV (export only) with relative time and sample voltage
  • JSON: data array (float sample values), sampling period, capture timestamp and used trigger type; for loading JSON files identical data structure is required
  • MS3: custom binary format with some similarities to AVI; allows efficient storing and browsing up to 10^9 samples per file
  • saving plot area image as 8-bit bitmap

Triggers

  • manual: captures single frame (i.e. 4096 samples) when activated
  • slope up/down: detects voltage change across selected value; trigger values below 0% are ignored (use 0% - 100% range only)
  • continuous: when started captures samples frame after frame until stopped