Logic Command
The logic command configures the logic analyzer core, and can display logic capture graphs directly in the terminal. It supports the “follow along” logic analyzer mode that triggers each time you send data to a bus. It eliminates the need setup triggers and arm a second tool for debugging.
The Bus Pirate can be used as a logic analyzer in multiple ways. This page documents the logic command in the terminal.
All Bus Pirate hardware supports the follow along logic analyzer, however only Bus Pirate 6 has a second buffer for the follow along mode. In earlier hardware all output pins are measured behind the IO buffer. This means the logic capture may not match the actual output of the IO buffer. This is not a problem when the Bus Pirate is used as a logic analyzer only and all pins are inputs.
Capabilities
- 62.5MSPS (or more if overclocked)
- 131K samples
- 8 channels
- Trigger: single pin, high or low
- Follow along logic analyzer mode
- Base pin can be set to an internal pin for debugging the Bus Pirate itself
Latest Features and Help
SPI> logic -? h usage: logic analyzer usage logic [start|stop|hide|show|nav] [-i] [-g] [-o oversample] [-f frequency] [-d debug] start logic analyzer: logic start stop logic analyzer: logic stop hide logic analyzer: logic hide show logic analyzer: logic show navigate logic analyzer: logic nav configure logic analyzer: logic -i -o 8 -f 1000000 -d 0 undocumented: set base pin (0=bufdir, 8=bufio, 20=follow along) -b: logic -b 20 logic analyzer control start start logic analyzer stop stop logic analyzer hide hide logic graph show show logic graph nav navigate logic graph with arrow keys, x to exit -i show configuration info -o set oversample rate, multiplies the sample frequency -f set sample frequency in Hz -0 set character used for low in graph (ex:_) -1 set character used for high in graph (ex:*) -d set debug level: 0-2 -h Get additional help SPI>
logic -h will display the help menu with the latest options for the logic command.
Start Logic Analyzer
logic start configures the logic analyzer core for follow along mode and draws a blank logic graph. Use logic stop to stop the logic analyzer and release any resources used.
The logic command and the follow along binmode interface can be run at the same time. However, the capture buffer is shared with SUMP logic analyzer mode. SUMP and follow along logic analyzer modes cannot be used at the same time and will result in a memory error warning.
Show/Hide Logic Graph
If the graph isn’t needed, use logic hide to release it from the toolbar. Use logic show to draw the graph again showing the current capture buffer.
Auto Capture Speed
Actual speed: 10kHz Logic analyzer speed: 80000Hz (8x oversampling) Use the 'logic' command to change capture settings Mode: SPI SPI>
When changing protocol modes with the m command, FALA will automatically set the capture speed to oversample the bus speed by a factor of 8.
Change Capture Speed
SPI> logic -o 16 Oversample rate set to: 16 Logic Analyzer settings Oversample rate: 16 Sample frequency: 10000Hz Note: oversample rate is not 1 Actual sample frequency: 160000Hz (16 * 10000Hz) SPI>
The base capture speed or the oversample rate can can be changed with the logic command. Changing the oversample rate with the -o flag is probably easiest as the Bus Pirate will calculate the new sample frequency for you.
Capture Samples
SPI> [ 0xaa 0x55] CS Enabled TX: 0xAA 0x55 CS Disabled Logic analyzer: 144 samples captured SPI>
Every time you send data to the bus, the logic analyzer will capture samples and the logic graph will update (if visible).
Currently the logic command only supports automatic capture in follow along mode. It does not currently support pin triggers, but it will eventually. Use logic -h to see the most recent features.
Navigation
If there are too many samples to display at once, use logic nav to navigate the graph. The arrow keys will move the graph left and right, and x will exit the navigation mode.
Logic Analyzer System
The logic command and the follow along binmode interface can be run at the same time. However, the capture buffer is shared with SUMP logic analyzer mode. SUMP and follow along logic analyzer modes cannot be used at the same time and will result in a memory error warning.