USBTMC

A USB Test & Measurement Class (USBTMC) instrument with USB488/SCPI support, behaving like a simple programmable instrument.

What it does

• Implements a USBTMC interface with USB488 capabilities and advertises SCPI support.
• Responds to *IDN? with an identification string (TinyUSB,ModelNumber,SerialNumber,FirmwareVer123456).
• Buffers other written messages and echoes them back as the query response, after a configurable delay.
• A delay <ms> command adjusts that simulated response delay (0–10000 ms).
• Maintains an IEEE-488.2 status byte (MAV/SRQ), and handles trigger, clear, and bulk abort requests.
• Supports the USBTMC indicator-pulse request, which briefly pulses the board LED.
• Uses an interrupt endpoint in addition to the bulk IN/OUT endpoints.

USB Descriptors

Configuration

Notable tusb_config.h settings:

#define CFG_TUD_USBTMC                1
#define CFG_TUD_USBTMC_ENABLE_INT_EP  1
#define CFG_TUD_USBTMC_ENABLE_488     1

Building

CMake:

mkdir build && cd build
cmake -DBOARD=raspberry_pi_pico ..
cmake --build .

Make:

make BOARD=raspberry_pi_pico all

Try it

The device appears as a USBTMC test-and-measurement instrument. Talk to it with a VISA/SCPI tool (for example PyVISA). The included visaQuery.py opens the instrument and sends *IDN?:

python visaQuery.py