PSoC® Creator™ Component Datasheet Resistive Touch (ResistiveTouch) 1.20 Features Supports 4-wire resistive touchscreen interface Supports the Delta Sigma Converter for both the PSoC 3 and PSoC 5 devices Supports the ADC Successive Approximation Register for PSoC 5 devices General Description This resistive touchscreen component is used to interface with a 4-wire resistive touch screen. The component provides a method to integrate and configure the resistive touch elements of a touchscreen with the emWin Graphics library. It integrates hardware-dependent functions that are called by the touchscreen driver supplied with emWin when polling the touch panel. This component is designed to work with the SEGGER emWin graphics library. This graphics library is provided by Cypress to use with Cypress devices and is available on the Cypress website at www.cypress.com/go/comp_emWin. This graphics library provides a full-featured set of graphics functions for drawing and rendering text and images. When to Use a ResistiveTouch Use a ResistiveTouch component where low cost and simple interface electronics are required. Input/Output Connections This section describes the various input and output connections for the ResistiveTouch. xm – Digital Input / Output Signal x– from axis X of the resistive touch panel (active low). xp – Analog / Digital Output Signal x+ from axis X of the resistive touch panel (active high). Cypress Semiconductor Corporation • 198 Champion Court • San Jose, CA 95134-1709 • 408-943-2600 Document Number: 001-85080 Rev. ** Revised December 7, 2012 Resistive Touch (ResistiveTouch) PSoC® Creator™ Component Datasheet ym – Digital Input / Output Signal y– from axis Y of the resistive touch panel (active low). yp – Analog / Digital Output Signal y+ from axis Y of the resistive touch panel (active high). Component Parameters Drag a ResistiveTouch component onto your design and double click it to open the Configure dialog. ADC The ADC parameter determines which ADC to use. For PSoC 3 devices, select the Delta Sigma ADC option. Application Programming Interface Application Programming Interface (API) routines allow you to configure the component using software. The following table lists and describes the interface to each function. The subsequent sections cover each function in more detail. Page 2 of 9 Document Number: 001-85080 Rev. ** PSoC® Creator™ Component Datasheet Resistive Touch (ResistiveTouch) By default, PSoC Creator assigns the instance name “ResistiveTouch_1” to the first instance of a component in a given design. You can rename it to any unique value that follows the syntactic rules for identifiers. The instance name becomes the prefix of every global function name, variable, and constant symbol. For readability, the instance name used in the following table is “ResistiveTouch”. Function Description ResistiveTouch_Start() Calls the ResistiveTouch_Init() and ResistiveTouch_Enable() APIs. ResistiveTouch_Stop() Stops the DelSig ADC or SAR ADC and stops the AMux component. ResistiveTouch_Init() Calls the Init functions of the DelSig ADC or SAR ADC and AMux components ResistiveTouch_Enable() Enables the DelSig ADC or SAR ADC and enables the AMux component. ResistiveTouch_ActivateY() Configures the pins for measurement of Y-axis. ResistiveTouch_ActivateX() Configures the pins for measurement of X-axis. ResistiveTouch_TouchDetect() Detects a touch on the screen. ResistiveTouch_Measure() Returns the result of the A/D converter. ResistiveTouch_SaveConfig() Saves the configuration of the DelSig ADC or SAR ADC. ResistiveTouch_Sleep() Prepares the DelSig ADC or SAR ADC for low-power modes by calling SaveConfig and Stop functions. ResistiveTouch_RestoreConfig() Restores the configuration of the DelSig ADC or SAR ADC. ResistiveTouch_Wakeup() Restores the DelSig ADC or SAR ADC after waking up from a low-power mode. Global Variables Variable ResistiveTouch_initVar Description Indicates whether the ResistiveTouch has been initialized. The variable is initialized to 0 and set to 1 the first time ResistiveTouch_Start() is called. This allows the component to restart without reinitialization after the first call to the ResistiveTouch_Start() routine. If reinitialization of the component is required, then the ResistiveTouch_Init() function can be called before the ResistiveTouch_Start() or ResistiveTouch_Enable() function. ResistiveTouch_enableVar This variable is used to indicate enable/disable component state. ResistiveTouch_measureVar This variable is used to indicate measure function call. Document Number: 001-85080 Rev. ** Page 3 of 9 Resistive Touch (ResistiveTouch) PSoC® Creator™ Component Datasheet void ResistiveTouch_Start(void) Description: Calls ResistiveTouch_Init() and ResistiveTouch_Enable() APIs. Parameters: None Return Value: None Side Effects: None void ResistiveTouch_Init(void) Description: Calls the Init functions of the DelSig ADC or SAR ADC and AMux components. Parameters: None Return Value: None Side Effects: None void ResistiveTouch_Enable(void) Description: Enables the DelSig ADC or SAR ADC and enables the AMux component. Parameters: None Return Value: None Side Effects: None void ResistiveTouch_Stop(void) Description: Stops the DelSig ADC or SAR ADC and stops the AMux component. Parameters: None Return Value: None Side Effects: None void ResistiveTouch_ActivateX(void) Description: Configures the pins for measurement of X-axis. Parameters: None Return Value: None Side Effects: Page 4 of 9 None Document Number: 001-85080 Rev. ** PSoC® Creator™ Component Datasheet Resistive Touch (ResistiveTouch) void ResistiveTouch_ActivateY(void) Description: Configures the pins for measurement of Y-axis. Parameters: None Return Value: None Side Effects: None int16 ResistiveTouch_Measure(void) Description: Returns the result of the A/D converter. Parameters: None Return Value: int16: The result of the ADC conversion Side Effects: None uint8 ResistiveTouch_TouchDetect(void) Description: Detects a touch on the screen. Parameters: None Return Value: uint8: The touch state 0 – untouched 1 – touched Side Effects: None void ResistiveTouch_SaveConfig(void) Description: Saves the configuration of the DelSig ADC or SAR ADC. Parameters: None Return Value: None Side Effects: None void ResistiveTouch_RestoreConfig(void) Description: Restores the configuration of the DelSig ADC or SAR ADC. Parameters: None Return Value: None Side Effects: None Document Number: 001-85080 Rev. ** Page 5 of 9 Resistive Touch (ResistiveTouch) PSoC® Creator™ Component Datasheet void ResistiveTouch_Sleep(void) Description: Prepares the DelSig ADC or SAR ADC for low-power modes by calling SaveConfig and Stop functions. Parameters: None Return Value: None Side Effects: None void ResistiveTouch Wakeup(void) Description: Restores the DelSig ADC or SAR ADC after waking up from a low-power mode. Parameters: None Return Value: None Side Effects: None MISRA Compliance This section describes the MISRA-C:2004 compliance and deviations for the component. There are two types of deviations defined: project deviations – deviations that are applicable for all PSoC Creator components specific deviations – deviations that are applicable only for this component This section provides information on component-specific deviations. Project deviations are described in the MISRA Compliance section of the System Reference Guide along with information on the MISRA compliance verification environment. The Resistive Touch component has not been verified for MISRA-C:2004 coding guidelines compliance. Sample Firmware Source Code PSoC Creator provides many example projects that include schematics and example code in the Find Example Project dialog. For component-specific examples, open the dialog from the Component Catalog or an instance of the component in a schematic. For general examples, open the dialog from the Start Page or File menu. As needed, use the Filter Options in the dialog to narrow the list of projects available to select. Refer to the “Find Example Project” topic in the PSoC Creator Help for more information. Page 6 of 9 Document Number: 001-85080 Rev. ** PSoC® Creator™ Component Datasheet Resistive Touch (ResistiveTouch) Functional Description This component provides a 4-wire resistive touch screen interface to read touchscreen coordinates and measure screen resistance. This component provides access to the touchscreen functionality of the SEGGER emWin graphics library for translation of resistance to screen coordinates. The diagram that follows shows the schematic of a 4-wire touchscreen when pressure is applied. YP RY+ YN RYRtouch XN Rx- Rx+ XP The point of contact “divides” each layer in a series resistor network with two resistors (see the diagram), and a connecting resistor between the two layers. By measuring the voltage at this point, you get information about the position of the contact point orthogonal to the voltage gradient. To get a complete set of coordinates, you must apply the voltage gradient once in the vertical and then in the horizontal direction. First, you must apply a supply voltage applied to one layer and perform a measurement of the voltage across the other layer; next connect the supply to the other layer and measure the opposite layer voltage. When in touch mode, one of the lines is connected to detect touch activity. The following table defines the configuration of the pins while measuring the coordinates or touch. XP XM YP YM touch Res Pullup Analog Hi-Z Analog Hi-Z Strong Drive X-Coordinate Strong Drive Strong Drive Analog Hi-Z Analog Hi-Z Y-Coordinate Analog Hi-Z Analog Hi-Z Strong Drive Strong Drive Document Number: 001-85080 Rev. ** Page 7 of 9 Resistive Touch (ResistiveTouch) PSoC® Creator™ Component Datasheet When a ResistiveTouch component is placed onto the project schematic, it is important that I/O port designations be set for xm, xp, ym, yp pins. Designation of these pins is not done on the symbol or schematic; instead, it is done in the Pins tab of the Design-Wide Resources window. References Refer also to the Delta Sigma ADC and SAR ADC component datasheets. Resources Depending on the configuration, the ResistiveTouch component uses the Delta Sigma ADC or SAR ADC component, and four pins. API Memory Usage The component memory usage varies significantly, depending on the compiler, device, number of APIs used and component configuration. The following table provides the memory usage for all APIs available in the given component configuration. The measurements have been done with the associated compiler configured in Release mode with optimization set for Size. For a specific design the map file generated by the compiler can be analyzed to determine the memory usage. PSoC 3 (Keil_PK51) Configuration PSoC 5 (GCC) PSoC 5LP (GCC) Flash SRAM Flash SRAM Flash SRAM Bytes Bytes Bytes Bytes Bytes Bytes Delta Sigma ADC 1459 20 2044 40 1764 28 SAR ADC N/A N/A 1028 14 1028 13 DC and AC Electrical Characteristics Depending on configuration the resistive touch component uses the Delta Sigma ADC or SAR ADC components. Therefore the resistive touch component is limited by the performance of these components. Refer to the Characteristics section of the associated ADC component datasheet for details. Page 8 of 9 Document Number: 001-85080 Rev. ** PSoC® Creator™ Component Datasheet Resistive Touch (ResistiveTouch) Component Changes Version 1.20 Description of Changes Added MISRA Compliance section. Reason for Changes / Impact The component was not verified for MISRA compliance. Updated for compatibility with PSoC Creator v2.2 1.10.a Minor edits and updates to datasheet 1.10 Added PSoC 5LP support © Cypress Semiconductor Corporation, 2012 The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in lifesupport systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. PSoC® is a registered trademark, and PSoC Creator™ and Programmable System-on-Chip™ are trademarks of Cypress Semiconductor Corp. All other trademarks or registered trademarks referenced herein are property of the respective corporations. Any Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign), United States copyright laws and international treaty provisions. 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Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in lifesupport systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. Use may be limited by and subject to the applicable Cypress software license agreement. Document Number: 001-85080 Rev. ** Page 9 of 9