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.

Comments

  1. Phrewfuf says:

    isn’t it possible to use level converters? I’ve seen some speciallized chips for that.

  2. jefffffff says:

    Could a possible use for this be to capture IR signals sent from an IR remote… Or even keystrokes?

  3. indiantinker says:

    I ought to try this.. This is just great.At the end i will have a 5$ Logic analyzer !
    Thanks!

  4. Blake says:

    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!

  5. Rudy says:

    Anybody else getting incorrect measurements from this? My oscilloscope reads 38kHz and OLS reads 66.667 kHz.

    • jpa says:

      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..

  6. Bob Paddock says:

    (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.

  7. Drone says:

    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.

  8. Lee says:

    If anyone’s interested I’ve made a minor modification to the code to use more of the stellaris’s ram. Capture length is increased from 1.64ms to 3.17ms.
    You can find it here: http://www.sodnpoo.com/posts.xml/longer_buffer_for_stellaris_logic_analyser.xml

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