Fieldscale and ST Introduce Simulation Software for STM32-based Capacitive Touch Sensors

January 28, 2020 by Gary Elinoff

Fieldscale’s SENSE simulation software allows OEMs to develop touch-enabled devices with far less hardware prototyping.

STMicroelectronics has partnered with Fieldscale, an ST authorized partner and developer of simulation software, to develop Fieldscale SENSE. This platform aims to help OEMs develop touch-enabled user interfaces for products based on ST’s ubiquitous STM32 MCUs


Fieldscale SENSE supports STM32

Fieldscale SENSE supports STM32. Image used courtesy of STMicroelectronics

Fieldscale SENSE is a cloud-based development platform that employs electromagnetic algorithms to accurately predict system performance. Because fewer actual hardware prototypes will be needed, OEMs can not only lower development costs but also decrease overall time to market. 


Using Fieldscale SENSE

Fieldscale SENSE is designed to support the development of capacitive touch sensors for ST’s STM32F0, STM32F3, STM32L0, STM32L4, STM32L5, and STM32WB MCUs.

Because Fieldscale SENSE is a cloud-based development platform—and not PC-based—installation challenges and system-performance limitations are eliminated. Simulation results have been measured to be within 2% of the final products produced by touch-sensor manufacturers.


Fieldscale SENSE

Fieldscale asserts that SENSE is the industry's only online CAD, "optimized for designing capacitive touch sensors." Image used courtesy of Fieldscale


Before they put anything to hardware, designers of capacitance touch sensors will be able to:

  • Import or design layouts as a standard drawing exchange format (DXF) or Gerber file(s) 
  • Build the 3D model of the sensors with Fieldscale SENSE automatically applying boundary conditions
  • Predict the touch sensor’s performance for users wearing gloves or using a stylus
  • Inject RF noise into the simulation to ascertain noise immunity
  • Predict and eliminate coupling between the traces and electrodes


Combining Layout with Controller

ST has provided Fieldscale with electrical models for the touch-sensing controller peripherals of its MCUs. These include the exact specifications and behaviors of ST MCU pins and controllers.

In turn, Fieldscale has integrated this information within their own mathematical models, resulting in accurate performance simulations. 


SENSE platform

ST explains, "SENSE users can start from its library of patterns or import Gerber or DXF files to begin with an existing layout from a reference design or development board." Image used courtesy of STMicroelectronics


The user selects which STM32 will be employed and SENSE will then generate templates for pin configurations, clock settings, and other relevant parameters. SENSE bridges the gap between the first steps with the controller and MCU defined in the latter stages.

The result is an overall system configuration closely replicating real-world performances.

Because the software is privy to the behavior of the touch sensing controller peripherals of ST MCUs, SENSE can, for example, aid designers in configuring the drain power voltage, resistance, and capacitance values for various pins.


Fieldscale SENSE in Action: a Use Case

The first step is to simulate the physical model of the sensor and to extract its equivalent circuit in a netlist format. Then the counts from the STM32 MCU are simulated just as they would be measured in the lab. The touch sensor is readily evaluated with no need to build and test a physical prototype.

Next, a sensor virtual model is built from the user's design or by using elements such as circular buttons from SENSE’s library.

The user then builds the 3D model of the sensor by a process that includes choosing the thickness and relative permittivity of the layers of the sensor being designed. Electrodes, traces, and shields are placed and connections are specified.


Delta Counts between touch and no-touch

Delta Counts between touch and no-touch. Image used courtesy of STMicroelectronics

The software then predicts the behavior of the model as it interacts with human inputs. The circuit representation of the touch sensor being designed is extracted into a netlist file.

The inputs and outputs of the sensor that are going to be connected to the controller are described herein.


What the Partners are Saying

As described by Yiorgos Bontzios, PhD, Fieldscale CEO and Co-Founder, “At Fieldscale, our goal is to offer to all capacitive-touch design engineers a complete software solution supporting them end-to-end, from the early design up to the tuning of the final system. Integrating STM32 support is a major achievement towards this goal and we couldn’t be more satisfied.” 

Patrice Hamard, Microcontroller Product Marketing Manager, STMicroelectronics, added, “Customers using our STM32 microcontrollers can now take full advantage of Fieldscale SENSE to implement simple and intuitive touch-based controls for smart devices and give their products a competitive edge.”