FHDM's DSO-500K Turns a Raspberry Pi Pico W Into a Wi-Fi Oscilloscope with Android Interface

Clever carrier board provides a two-channel oscilloscope — or your can roll your own analog front end for an existing Raspberry Pi Pico.

Gareth Halfacree
2 years agoDebugging / HW101

Australia's FHDM TECH has designed a carrier board to turn a Raspberry Pi Pico W into a Wi-Fi-equipped two-channel oscilloscope and signal generator, using an Android smartphone or tablet as its user interface: the DSO-500K.

"The DSO-500K is an affordable two-channel 500kS/s [kilo-samples per second] oscilloscope with a maximum analog bandwidth of 150kHz," FHDM explains of its board design, brought to our attention by CNX Software. "The highly rated Scoppy Android app is used to control the scope and display the waveform data."

The board, which includes a Raspberry Pi Pico W installed as a surface-mount module, offers up to 500kS/s on a single channel or 250kS/s each when using both channels, with a 150kHz analog bandwidth. It can record up to 2,048 samples per channel in run mode with 100kS recording for single-shot captures.

Unlike most oscilloscopes, the DSO-500K lacks a display. Instead, it's designed for use with FHDM's Scoppy Android app — providing a touch-screen user interface and a number of display modes for the captured samples. It also provides access to the DSO-500K's signal generation capabilities, pushing square waves up to 1.25MHz or sine waves up to 1kHz. Finally, there's a logic analyzer mode operating at 25MS/s — though, the company notes, it currently lacks protocol decoding capabilities.

Being based around the low-cost Raspberry Pi Pico W and its RP2040 microcontroller does bring a few limitations, though, and it's not just in the peak performance stakes. FHDM warns that the board, which offers a 1MΩ/22pF input impedance, cannot be used for measuring high-voltage signals - "even with 10X or 100X probes," the company continues.

The DSO-500K is available to purchase on FHDM's Tindie store at $33.50, including an upgrade license to unlock the second channel of the Scoppy Android app and a pre-installed Raspberry Pi Pico W. Headers for the logic analyzer mode, however, are not included. Those on a budget can use the Scoppy app and firmware on a Raspberry Pi Pico via USB without the DSO-500K carrier, though the company recommends building an analog front end to expand its capabilities.

More information on the DSO-500K and Scoppy is available on the FHDM GitHub repository.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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