As we all know, Cypress is the world leader in capacitive touch sensing, with the industry's broadest product line, and its PSoC-based CapSense device delivers unmatched flexibility and integration with robust noise immunity. Suitable for all types of touch designs from complex, versatile applications to alternative single buttons.

Compared to the mechanical buttons that we are common but can't keep up with the times, the advantages of touch buttons are obvious, such as:

Due to the movement of the physical position, the reliability of the mechanical buttons is low and wear occurs over time. But touch buttons don't have this kind of trouble.

Mechanical buttons are not easily waterproof and can cause undesirable problems. However, the touch button can be used to isolate an unexpected condition through the overlay.

Compared with the touch, the mechanical button needs to be pressed hard to work, and dirt will accumulate in the gap over time, resulting in increasing the pressing force.

Compared with mechanical buttons, the touch buttons look more stylish and so on, etc.

With these many reasons, in today's electronics market, industrial designs such as mobile phones, personal computers, consumer electronics, automobiles and white goods can see the active touch buttons.

Cypress PSoC 4000S CapSense Prototyping Kit

This 2017 Mouser Electronics Smart Innovation Competition won the Cypress-sponsored CY8CKIT-145-40XX PSoC 4000S CapSense Prototyping Kit, a board based on Cypress's fourth-generation touch technology.

PSoC 4 CapSense original development board PCB design is somewhat unique, the shape has a kind of Dapeng wings, very exaggerated, the board uses a similar USB dongle interface type, directly plugged into the computer's USB interface can be used.

After disassembling the outer packaging, you can see a very inspiring word "Design the way you think". Don't think that this is a simple slogan. Aiban.com engineers think this is very suitable for Cypress's product features. , PSoC, you can program the system on chip, you can completely define the corresponding pin signal according to your own design, to create the most reasonable design.

The whole board is not large, and can be roughly divided into three parts according to the function: the target board with the core device PSoC 4 Capsense device; one KitProg onboard programmer and debugger and two capacitive boards.

The capacitive board can be divided into two parts: one is three capacitive buttons, and the other is a five-stage capacitive slider.

The onboard resources of the Cypress PSoC 4000S CapSense Prototyping Board are as follows:

PSoC 4000S device (CY8C4045AZI-S413)

PSoC 4000S Extended I/O

10-pin download debugging interface (not patched)

KitProg2 (PSoC 5LP) device (CY8C5868LTI-LP039)

KitProg2 extended I / O port

5-pin SWD interface

PCB USB finger interface

EZ-BLETM PRoCTM Module

A single-pole, single-throw switch selects the target device for SWD debugging

A user led, a power led, a KitProg2 status led and touch button corresponding LED indicator

One user button, one PSoC 4000S and EZ-BLE module reset button, one KitProg2 button

Current test interface (not patched)

CapSense touch buttons, sliders

Thanks to the snap-on construction, the KitProg on-board programmer and debugger can be used directly and separately. In addition to download debugging, KitProg can also be used for U disk downloads like mebed, which is very convenient.

PSoC 4000S CapSense Touch Controller

Onboard Cypress PSoC 4000S CapSense touch controller, the specific model is CY8C4045AZI-S413, based on ARM Cortex-M0+ processor, the maximum frequency is 48MHz, integrated 32KB FLASH, 4KB SRAM, and supports 1 10bt single- Slope ADC, 8 comparators, 2 IDACs, 5 timer/counter/PWM, 2 serial interfaces, 1 CapSense module, up to 36 GPIO port expansions.

CapSense touch sensing principle

The hardware design of the CapSense touch sensing solution mainly includes touch sensors, PCBs, and overlays, as shown in the structure below.

CapSense, as its name implies, detects changes in capacitance to touch a finger or touch the touch surface. In Cypress's specific touch solution design, it can be divided into self-capacitance sensing or mutual capacitance sensing technology.

The diagram on the left side of the figure above shows the principle of self-capacitance sensing. The self-capacitor uses a pin and measures the capacitance between the pin and the power ground, drives the current on the pin connected to the sensor, and measures the voltage. If you put your finger on the sensor, the measured capacitance will increase. Self-capacitance sensing is best suited for single-touch sensors such as buttons and sliders.

The diagram on the right in the above figure is the principle of mutual capacitance sensing technology. The mutual capacitance sensing will measure the capacitance between two electrodes. One of the electrodes is called the transmitting electrode TX and the other is called the receiving electrode RX.

In a mutual capacitance measurement system, provide a digital voltage (signal switching between VDDD and GND) for the TX pin and measure the charge received on the RX pin. The charge received on the RX electrode is proportional to the mutual capacitance (CM) between the two electrodes.

When placing a finger between the TX and RX electrodes, the mutual capacitance is reduced to C1M (as shown in the figure below), and the charge received on the RX electrode is also reduced due to the decrease in mutual capacitance. The CapSense system detects touch/no touch status by measuring the charge received on the RX electrode. The mutual capacitance effect is best suited for multi-touch systems such as touch screens and trackpads.

The PSoC 4000S CapSense touch controller enables a wide range of touch control solutions, the simplest of which is touch, as well as slider touch and proximity touch.

Cypress BLE PRoC module

In addition, in order to facilitate user development, the PSoC 4 CapSense prototype development board will bring out all the IO ports, and even more surprising is that the back of the board actually has a BLE module! ! !

Take a look at the Cypress BLE PRoC module, the specific model is CYBLE-022001-00 module, support BLE 4.1 protocol stack, the size is only 10mm * 10mm * 1.8mm, very small, but contains ADC, timer, counter function and support PWM , I2C, UART, SPI peripherals, can be defined by the programmable architecture of PSOC.

The Cypress BLE PRoC module has an operating current TX of 15.6 mA @0 dbm and an RX of 16.4 mA. This power consumption can only be said to be normal, if it is much higher than the previous Silicon Labs Thunderboard Sense (EFR32MG1).

The hardware block diagram of the entire board is as follows:

It can be seen that the SWD signal download debugging used by the board's debugger can be downloaded to the touch control chip or the BLE module through the onboard SW4 switch .