# New firmware for our pick & place, and a placement error cut by a factor of five | OneStack > Case study: we replaced the controller firmware of a desktop pick & place to run it with OpenPnP. It now assembles our prototypes. URL: https://www.onestack.it/en/case-studies/pick-and-place-openpnp [← All case studies](/en/case-studies)In-house R&D · lab # New firmware for our pick & place, and a placement error cut by a factor of five Our lab started with a closed, imprecise desktop pick & place. We replaced its controller firmware to run it with OpenPnP and calibrated it nozzle by nozzle. It is still the machine we assemble prototypes on. ![3D render of a pick-and-place controller board: STM32F4 microcontroller, stepper motor drivers and connectors for axes, vacuum, lights and feeders](/_astro/controller-pnp.3whQaHFS_ZhBMRk.webp)![](/_astro/controller-pnp-xray.CMO0PqBP_1JH2KI.webp) 0.194 → 0.036 mm placement error, before and after calibration 0402 passives placed automatically Architecture after the conversion **Assembly files**BOM and coordinates from CAD **OpenPnP on the PC**jobs · fiducials · vision **USB cameras**top and bottom **Controller firmware**STM32F4 bare-metal · G-code over UART **Mechanics**axes · Z cam · vacuum · feeders ## Context Our lab started with a desktop pick & place. The machine had closed firmware, could only be programmed from its touch screen and had no link to a PC. Every board had to be set up by hand, and the accuracy was not enough for the smallest passives. ## The problem Replacing the firmware of a working machine means touching motors, vacuum and cameras without any documentation from the manufacturer. A mistake can brick the machine or damage the head. And once reprogrammed, accuracy depends on calibration: a motion model off by a few hundredths of a millimetre is enough to move an 0402 off its pads. ## Technical choices, and why **Backup first.** We saved the original firmware and checked the memory protection before writing anything, so the conversion stayed reversible. **Bare-metal firmware that speaks G-code.** We started from an open-source project for the STM32F4 controller and extended it. The machine receives G-code on the serial port that used to drive the display, and a PC running OpenPnP becomes its control panel: jobs come straight from the CAD files. **Cam-driven Z axis handled in firmware.** The two nozzles share a single motor that turns a cam. The controller converts between linear height and rotation, so for OpenPnP the axis is an ordinary one. **New cameras and bottom vision.** The original cameras processed images on board and could not be accessed. We replaced them with USB cameras: each part is photographed on the nozzle and corrected in position and rotation before it is placed. **Nozzle-by-nozzle calibration.** The residual error was not random: the two nozzles shifted parts in opposite directions. We measured it at 12 angles, corrected each nozzle separately, and moved the camera focus to the placement height. ## How we verified it - Placement error measured with the machine camera after each correction round, on real pads and parts. - Repeatability of the fiducial check on the board. - A verification pause after each alignment during tuning, with a re-measurement on the same part. ## Result The placement error went from **0.194 to 0.036 mm**, below the camera resolution, with passives down to **0402**. It is still the machine we assemble prototypes on: jobs start from the design files, with nothing set up by hand. ## What we bring to your projects Bare-metal firmware on STM32, motor and actuator control, serial protocols, and the method we used to find the error: measure, separate the causes and fix them one at a time. ## Services - Firmware development ## Technologies - STM32F4 - Bare-metal - G-code over UART - OpenPnP - Bottom vision - Per-nozzle calibration ## More case studies [ ![3D render of the control board: microcontroller in the centre, connectors for the two isolated channels on the side, pluggable terminal blocks and power and service connectors](/_astro/interfaccia-rugged.CkQk4iYb_1A6Ozp.webp)![](/_astro/interfaccia-rugged-xray.CZb6dpZZ_Z1kxhOu.webp) 23 tests in ~75 s Systems for harsh environments ### A rugged interface that updates in the field and never bricks A portable, battery-powered unit that powers and controls two remote devices over isolated channels. 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