Sparkfun started selling the 500Msamples/sec Saleae Logic Pro 8 logic analyzer today for $399. Each of the Logic Pro 8’s eight multi-use inputs can serve as a digital input at the full sample rate or as a 10-bit, 50Msamples/sec analog input with a 1MHz input bandwidth. The analyzer’s digital input range is 1.2 to 5.5V and the analog input range is 0 to 5V. This thing is tiny! It measures just over two inches (53mm) on a side and is less than half an inch (12mm) thick. “Gotta be an FPGA in there,” I thought.
Fortunately, Saleae is very proud of the design and craftsmanship that went into the development of the Logic Pro 8 and the company’s Web site carries this image:
That’s a Xilinx Spartan-6 LX16 FPGA prominently featured on the circuit board. This Spartan-6 FPGA incorporates 14,579 logic cells, 576Kbits of block RAM, and 32 DSP48A1 DSP slices—so it provides a lot of raw processing power to the instrument. (Click here to see the video.)
The logic cells and memory have obvious use in this application but what does Saleae need the DSP for? According to the Saleae Web site, “The FPGA also has the capability of performing over 5 billion DSP operations per second (over 10 billion on Pro 16). When you use more analog channels than can be streamed over USB at once, we need to filter and decimate that data in the FPGA – reducing the bandwidth without introducing aliasing. Logic Pro 16 produces analog data at a rate of 9.6Gbit – that’s a lot of data to process in real time!” (Yes, there’s a 16-channel version of the analyzer available as well. It has the same input specs but twice as many channels for an additional $100.)
(Note: The other large chip appearing on the board is a Cypress CY7C68013A High-Speed USB Peripheral Controller, which provides the Saleae Logic Pro 8 logic analyzer with its USB host connection.)