Turning the Stellaris Launchpad into a logic analyzer

acquisition

If you have a Stellaris Launchpad sitting around, have a go at using it as a logic analyzer

The Stellaris logic analyzer is based upon this earlier build that took code from a SUMP comparable Arduino logic analyzer and ported it to the much faster and more capable Stellaris Launchpad with an ARM Cortex 4F processor.

This build turns the Launchpad into a 10 MHz, 8-channel logic analyzer with a 16 kB  buffer comparable with just about every piece of software thanks to the SUMP protocol. Even though the ARM chip in the Launchpad isn’t 5 Volt tolerant, only pins 0 and 1 on Port B are limited to 3.6 Volts. All the other pins on Port B are 5 Volt tolerant.

Not a bad piece of work to turn a Launchpad that has been sitting on your workbench into a useful tool.

20 thoughts on “Turning the Stellaris Launchpad into a logic analyzer

    1. If you’re interested in keeping jitter (basically, not distorting the timing of the signals) to a minimum, as you generally do when using a logic analyzer then you would not use a level converter/re-driver.

      1. Interesting. Would simple voltage division be a good alternative there? I’ve used this to level shift serial comms with 3v3 components and the atmegas.

      2. I think this depends on how much you spend for the translator :D
        Though it is worth a try, even if it’s to find out if it will work as intended of have noticable failures. Sadly i only have 1.83.3V translators or i would’ve tried out on my own.

          1. The HAD page code interprets those symbols as a (broken) HTML tag and skips them. I hope there’s some way to add an escape code to show them, never tried though.

      3. Would it be possible to just put level converters on all inputs? since the delay would be equal then (or isn’t the delay as constant as I think it is?).

    1. That’s what logic analyzers are for. To capture the logic part of a communication. Hardware part is IR, logic part is some magic toggling of the IR-LED.

  1. This is awesome. I couldn’t justify the $150 for Saleae since I’m just playing around with this stuff, but $5? No problem! I already have a Launchpad sitting unused on my desk! Thanks for this!

      1. I actually picked up two Stellaris M4F Launchpads for $4.99 each from TI. I got in on an early introductory offer.

        You had me worried for a second!

    1. This is to be expected: the code appears to make absolutely no attempt at sampling at regular intervals. Instead it just uses a for loop and hardcoded “samplerate” that is not accurate. Considering this device has DMA and everything, it could be written much better. And run-length-encoding would make it a lot more useful..

  2. (74HC)4049 and (74HC)4050 have inputs that are tolerant to +15V, while running on ~3V supply.

    No need to go for esoteric for level-shifters for this application, when simple one will do.

  3. 10MHz 8 channel – pffft. Google OpenBench Logic Sniffer, FPGA based, 200Msps, $50, open-source. Use it with Jawi’s OLS client software which is derived from SUMP.

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