Capture Settings Configuration Guide; Collecting Data And Device Settings - Saleae Logic User Manual

Capture Settings Configuration Guide

The new Saleae devices are considerably more capable than the first generation (Logic and Logic16).
The new products have inputs that can be used to record analog, digital, or both. On all but Logic 4, this
is applicable to every channel on the device. That leads to many more sample rate options, which can be
confusing. In some cases, it makes it harder to decide the optimal capture configuration for your
application.
Because if this, we get a fair number of customer support questions about how to choose the optimal
capture configuration for an application. To help users determine the best setup for them, we're creating
this guide. The guide also contains a number of tips for recording with more complex requirements.
Please first review the Getting Started section, including the article on device settings:
Collecting Data & Device Settings
Generally, when starting a capture, make sure you record all the channels you have connected in the
correct mode (analog or digital). You also need to make sure you record sufficiently fast in order to
accurately record the signal and record long enough to locate the event(s) you are interested in.
However, meeting all of these requirements at the same time might not be easy or even possible in all
situations.
The devices are designed to stream the recorded data over USB in real time, to be recorded and
processed on a PC. That means that no matter what, the USB bandwidth limits the maximum sample rate
of the capture. However, you can make compromises. You can trade unused channels for faster sample
rates on the remaining channels, and you can sacrifice higher analog sample rates for faster digital
sample rates. Optimizing these trade-offs is required whenever you need to push the limits of the device.
Over USB 2.0, the maximum possible bandwidth for most of our products is 300 Mbps. For our USB 3.0
products, it's 2 Gbps. Each digital sample for each channel consumes 1 bit. The analog samples are
either 8 bit for Logic 4 or 12 bit for the new Logic 8, Logic Pro 8, and Logic Pro 16. (Although Logic 8 is
advertised as a 10-bit product, we maintain 12-bit samples through the entire process. The effective
number of bits, however, is closer to 10).
In addition to the limit of USB throughput, the installed RAM in the host PC is a limiting factor for how long
our software can record. To optimize for a long recording length, it's important to reduce the number of
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