2.2 Inch ILI9225G SPI & RGB Touch TFT LCD Screen，2.2" QCIF TFT LCD Display Module With Resistive Touch Panel

2.2 Inch ILI9225G SPI & RGB Touch TFT LCD Screen,2.2" QCIF TFT LCD Display Module With Resistive Touch Panel Product IntroductionSF-TC220I-9752C-T SPECIFICATION_IC-ILI9225G.pdf

Saef SF-TC220I-9752C-T is a 2.2 inch diagonal full color 176x220 QCIF TFT LCD display module. This 2.2 inch TFT LCD module is built in with ILI9225G IC; it supports 3 lines SPI and RGB Interface. SF-TC220I-9752C-T model is having module dimension of 41.7x56.16x3.35 mm and Active area size of 43.56 x 34.85 mm; it integrated ILI9225G controller on module, logic supply voltage range from 1.6V to 3.3V.
This 2.2” TFT LCD module is portrait mode, if you would like to use landscape mode please contact with us for more technical support. This 2.2" LCD module is featured with brightness up to 200 cd/m2(typical value), it can be operating at temperatures from -20℃ to +70℃; its storage temperatures range from -30℃ to +80℃.

SF-TC220I-9752C-T is a TFT screen 2.2" inch with Resistive Touch Screen (RTP) TFT LCD module, This lcd module is having anti-glare surface panel, view direction 12 o'clock, gray scale inversion 6 o'clock. The module also is available for without touch screen option whose part no. SF-TC220I-9752C-N. 

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Features: 

2.2 Inch ILI9225G SPI & RGB Touch TFT LCD Screen,2.2" QCIF TFT LCD Display Module With Resistive Touch Panel Product Drawing

2.2 Inch ILI9225G SPI & RGB Touch TFT LCD Screen,2.2" QCIF TFT LCD Display Module With Resistive Touch Panel Product Image

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LCD touch screen - Touch
1.1 Resistive touch screen
Before the advent of the iPhone, resistive touch screens were almost exclusively used, which used pressure sensing for contact detection control, requiring direct stress contact to locate the touch position by detecting the resistance.

The main part of the resistive touch screen is a resistive film screen that is very well matched with the surface of the display, which is a multi-layer composite film, which uses a layer of glass or hard plastic plate as the base layer, and the surface is coated with a transparent oxide metal (transparent conductive resistance) conductive layer, which is covered with a layer of outer surface hardening, smooth and anti-rub plastic layer, and its inner surface is also coated with a coating, and there are many small (less than 1/1000 inch) transparent isolation points between them to separate the two layers of conductive layer insulation. When the finger touches the screen, the two layers of conductive layers are in contact at the touch point, and the resistance changes, generating a signal in the X and Y directions, which is then sent to the touch screen controller. The controller detects this contact, calculates the position of (X,Y), and then simulates the behavior of the mouse based on the obtained position. This is the most basic principle of resistive technology touch screens.

The touch screen used by the author is a resistive touch screen, and its own touch screen control chip is XPT2046 (on the back of the LCD display U1 is the chip). XPT2046 is a 4-wire touchscreen controller (SPI communication) with a 12-bit resolution 125KHz slew rate step-by-step approximation A/D converter. XPT2046 supports low-voltage I/O interfaces from 1.5V to 5.25V. XPT2046 can detect the position of the pressed screen by performing two A/D conversions, and in addition to measuring the pressure applied to the touch screen. The operating temperature range is -40°C~+85°C.

The chip is fully compatible with ADS7843 and ADS7846, and you can refer to the datasheet of these two chips for detailed use of this chip.
Notes:

(1) When using the XPT2046 chip, directly use SPI communication (both software and hardware) to read the high 12-bit data output by the MISO terminal, and then read the X and Y coordinates through coordinate conversion and filtering operations; (This can be seen in the programming process)

(2) Due to its special physical properties, the basic use of resistive touch screen requires calibration of touch error, but the calibration data of resistive screen of the same type of LCD is roughly approximate;

(3) Due to the existence of a mechanism that needs to be calibrated for resistive touch screens, it is generally necessary to calibrate before use. Of course, we can use 24CXX (EEPROM) to save the calibration compensation parameters, and then we don't need to recalibrate every time we turn on the computer; (As a last resort, considering the cost, it is actually possible to save the calibration data in flash - not very recommended);

Advantages of resistive touch screen: high precision, low price, strong anti-interference ability, and good stability.
Disadvantages of resistive touch screen: easy to be scratched, light transmittance is not very good, and does not support multi-touch. (Datum correction is required, otherwise the offset is not small)

1.2 Capacitive touch screen
Nowadays, almost all smart phones, including tablet computers, use capacitive screen as touch screen, capacitive screen is the use of human body sensing for contact detection control, no direct contact or only slight contact, by detecting the induced current to locate the touch coordinates. (At present, basic capacitive touch screen is the mainstream)

There are two main types of capacitive touch screens:

1. Surface capacitive capacitive touch screen.

Surface capacitive touch screen technology uses ITO (indium tin oxide, a transparent conductive material) conductive film to sense the touch behavior of the screen surface through electric field sensing. But surface capacitive touchscreens have some limitations, they can only recognize one finger or one touch. (Less used)

2. Projected capacitive touch screen.

Projected capacitive touch screens are sensors that use touch screen electrodes to emit electrostatic field lines. There are two types of capacitance that are generally used in projected capacitive sensing technology: self-capacitance and interaction capacitance.

Self-capacitance, also known as absolute capacitance, is the most widely used method, and self-capacitance usually refers to the capacitance composed of a scanning electrode and ground. On the surface of the glass, there are transverse and longitudinal scanning electrodes made of ITO, and between these electrodes and the ground form a capacitive pole. When touched by hand or stylus, a capacitor is added in parallel to the circuit, thus changing the overall capacitance of the scan line.

Interaction capacitance, also known as spanning capacitance, forms a capacitance at the intersection of transverse and longitudinal ITO electrodes on the glass surface. The interactive capacitance scanning method is to scan the capacitance change at each intersection to determine the position of the touch point. When touched, it will affect the coupling of adjacent electrodes, thereby changing the capacitance at the intersection, and the scanning method of the interactive capacitance can detect the capacitance value of each intersection and the capacitance change after touching, so it requires a longer scanning time than the scanning method of self-capacitance, and it needs to scan and detect X*Y electrodes. At present, the touch screens of smartphones, tablets, etc., all use interactive capacitive technology. (The LCD of the author's punctual atomic elite board is a capacitive touch screen)

The transmissive capacitive touch screen uses two columns of electrodes in the vertical and horizontal columns to form a sensing matrix to sense touch. Two crossed electrode matrices, the X-axis electrode and the Y-axis electrode, are used to detect the capacitance change of each cell. The electrode in the picture is actually transparent, and it is here for the convenience of everyone. In the figure, the accuracy and resolution of the transparent electrode capacitive screen in the X and Y axes are related to the number of channels in the X and Y axes, and the more channels, the higher the accuracy.