mirror of git://sigrok.org/pulseview
135 lines
6.7 KiB
Plaintext
135 lines
6.7 KiB
Plaintext
== Data Acquisition
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Working with PulseView follows a pattern:
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image::pv_nodevice.png[]
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<1> Open a new session
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<2> Select the device you want to work with:
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<3> Click "Run" to acquire signal data (waiting for a trigger first if you set one)
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When you start PulseView and no sessions are restored from the last time you used it, it will
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come up with a session that has the demo device selected. That way, you can get to know the
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program even when you don't have any hardware to use it with.
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=== Device Selection
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The device selector offers two methods to choose the device to use. If you click on the small
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arrow on the side, you see a list of devices PulseView has recognized. If the device you want
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to use is listed, you can just select it here.
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image::device_selector_dropdown.png[]
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If it's not listed, you'll need to scan for it first. Since most serial port and Ethernet
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devices can't be auto-detected, this is usually required for those.
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To do so, either choose the "Connect to Device" option from the list or click on the button
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itself. You will see the following dialog:
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image::device_selector_scan.png[]
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First, you'll need to pick a driver that you want to use. In order to do this, you'll need
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to know which driver is used to talk to the device. If you're unsure, you can either try the
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driver which you think may fit best or you can check the wiki. For every supported device there's
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a wiki page, showing you which driver is used.
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Once the driver has been chosen, you need to select the interface. Please be aware that USB
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is only usable for devices that directly communicate over USB. Devices that use USB to emulate
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a serial port (like the OpenBench Logic Sniffer) will have their serial port listed in the
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serial port drop-down.
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In case your device connects via Ethernet, you must supply the IP address and port. You are
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also given the option to choose between raw TCP access and using the VXI protocol. VXI is an
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industry standard which is mainly used in professional equipment and the device will most
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likely let you know that it supports VXI. If your device however is more of a hobbyist grade
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device, it's more likely that using raw TCP will be the correct choice.
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After you selected the appropriate options, clicking the scan button will make PulseView try
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to connect to the device with the given settings. If successful, any device(s) found will be
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shown in the list box.
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[NOTE]
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When a session uses a USB device and you close Pulseview, a session with that same device
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is re-opened when you start Pulseview again. Currently, this is however not the case for non-USB
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devices, such as ones that connect via serial port or Ethernet.
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[NOTE]
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To avoid having to manually enter the device configuration for a serial port or Ethernet
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device every time you want to use it and then having to scan for it, you can also use the
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command line parameter -d to have PulseView scan for it on startup.
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You may then change the device configuration and/or start the data acquisition by clicking
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the "Run" button on the top left.
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When you run the acquisition, you'll notice that the newly captured data goes off-screen.
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This is to improve performance and let PulseView acquire the data without bogging down your
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CPU too much. If you find this inconvenient because you'd like to see what kind of data is
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coming in, you have three options:
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* Enable "always perform zoom-to-fit" temporarily (see chapter "Data Analysis")
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* Enable "constantly perform zoom-to-fit during acquisition" in the options
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* Enable "always keep newest samples at the right edge during capture" in the options
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Which method suits you best is up for you to decide.
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=== Device Configuration
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In PulseView, the device configuration is done using these buttons:
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image::pv_device_config.png[]
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<1> Device-specific settings
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<2> Channel-specific settings
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<3> Number of samples to capture
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<4> Sample rate at which to capture the samples
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<5> Per-channel trigger setting (see below)
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The values offered for those four elements depend on your device. Which settings you should choose
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depends on several factors: the needs of your measurement, the device you use to capture the data
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and the capabilities of your computer.
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The sample rate you choose must at least be twice that of the highest frequency you want to
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capture - ideally 3 to 5 times as much so that you have some margin. That way, a jittering signal
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won't ruin your measurements.
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[NOTE]
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If you're using a device with a Cypress FX2 (most 8 channel / 24 MHz logic analyzers do) then you should
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be aware that the 24 MHz sampling rate (12 MHz for 16 channels) can only be sustained under perfect
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conditions. Usually, those devices are shipped with low-quality USB cables, impairing USB transfers as
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USB traffic increases. Therefore, you can try a different USB cable if you're facing issues at higher
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sample rates. If they persist, it's worth trying a different USB port as well.
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=== Triggers
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The signal labels on the left side of the view (D0, D1 and so on in the picture above) allow you to
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configure certain aspects of these signals. If the device supports it then the trigger that will be
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used for this signal will be among them.
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As of now, the trigger system is awaiting extension for advanced and complex trigger types, meaning
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that the only triggers available to you are:
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* Trigger when the signal has a "low" level
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* Trigger when the signal has a "high" level
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* Trigger when the signal switches from "low" to "high" level (rising edge)
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* Trigger when the signal switches from "hig" to "low" level (falling edge)
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* Trigger when the signal changes level in any way (any edge)
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Once you choose a trigger, the icon for the type you chose becomes visible on the right side of the
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trace view.
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When you click "Run" with a trigger configured, PulseView will wait for the device to trigger and
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send data before it can show anything. There is currently no frame limit, so if the device driver
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supports it, PulseView will continue arming the trigger and collecting data until you either click
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"Stop" or it runs out of memory.
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=== Channel Groups
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Some devices share certain settings between a group of channels, which is why PulseView may show
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the channels your device offers in groups. You can see which channels are grouped by looking at the
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dark gray bar on the left. If there is none, no channels are grouped.
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Currently, the grouping is only done for your convenience and there's no direct functional impact.
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This means that you're free to ungroup and group channels as you please. To do so, right-click
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on the dark gray bar and select "Ungroup".
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If you want to create a new group, select the signals you want to group by holding down CTRL
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and clicking on the signal labels. Once you have selected the ones you want to be grouped,
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right-click on one of the labels you selected and choose "Group".
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