AT07899: SAM3S/4E/4S Analog Comparator Controller (ACC) Driver. Introduction. SMART ARM-based Microcontrollers APPLICATION NOTE

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1 SMART ARM-based Microcontrollers AT07899: SAM3S/4E/4S Analog Comparator Controller (ACC) Driver APPLICATION NOTE Introduction This driver for Atmel SMART ARM -based microcontrollers provides an interface for the configuration and management of the device's Analog Comparator Controller functionality. The Analog Comparator compares two voltages, and the result of this comparison gives a compare output. The user application can select whether to use a high-speed or a low-power option as well as selecting the hysteresis level, edge detection, and polarity. Devices from the following series can use this module: Atmel SMART SAM3S Atmel SMART SAM4E Atmel SMART SAM4S The outline of this documentation is as follows: Prerequisites Module Overview Special Considerations Extra Information Examples API Overview

2 Table of Contents Introduction Software License Prerequisites Module Overview Special Considerations Configuration Changes I/O Lines Power Management Interrupt Fault Output Extra Information Examples API Overview Macro Definitions Hysteresis Levels Function Definitions Function acc_disable() Function acc_disable_interrupt() Function acc_enable() Function acc_enable_interrupt() Function acc_get_comparison_result() Function acc_get_interrupt_status() Function acc_get_writeprotect_status() Function acc_init() Function acc_reset() Function acc_set_input() Function acc_set_output() Function acc_set_writeprotect() Extra Information for Analog Comparator Controller Acronyms Dependencies Errata Module History Examples for Analog Comparator Controller Quick Start Guide for the ACC driver Use Cases ACC Basic Usage

3 Setup Steps Usage Steps Analog Comparator Controller - Example Interrupt Event Generation Purpose Requirements Main Files Compilation Information Usage Document Revision History

4 1. Software License Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. The name of Atmel may not be used to endorse or promote products derived from this software without specific prior written permission. 4. This software may only be redistributed and used in connection with an Atmel microcontroller product. THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 4

5 2. Prerequisites There are no prerequisites for this module. 5

6 3. Module Overview The Analog Comparator Controller configures the Analog Comparator, and generates an interrupt according to the user application's settings. The analog comparator embeds 8 to 1 multiplexers on both its plus and minus inputs. The Analog Comparator compares two voltages, and the result of this comparison gives a compare output and an interrupt can be generated accordingly. The user application can select a high-speed or low-power option, the hysteresis level, edge detection, and polarity. The ACC can also generate a comparison event that can be used by the Pulse Width Modulation (PWM) module. 6

7 4. Special Considerations 4.1. Configuration Changes As soon as the analog comparator settings are modified, the output of the analog comparator is masked for the time that its output may be invalid. Depending on the user application the following function calls may require the comparator output to be valid before continuing: acc_enable() acc_set_input() acc_set_output() The following code may be used to check if the comparator output is valid before continuing: * while ((acc_get_interrupt_status(acc) & ACC_ISR_MASK) == ACC_ISR_MASK) { * } 4.2. I/O Lines The analog input pins (AD0-AD7 and DAC0-1) are multiplexed with general-purpose input/output (GPIO) lines. The assignment of these pins to ACC module inputs is automatically done when the corresponding input is assigned to the comparator's plus/minus inputs by the user application performing a write to the module's Mode Register Power Management The ACC module is clocked through the Power Management Controller (PMC), thus the user application must first configure the PMC, in order to enable the Analog Comparator Controller clock. Note: The voltage regulator must be activated before the Analog Comparator module is used Interrupt The ACC module has an interrupt line connected to the Nested Vectored Interrupt Controller (NVIC). Handling the ACC interrupt requires that the NVIC is configured before configuring the ACC Fault Output The ACC module has a FAULT output that is connected to the FAULT input of the PWM module. Refer to "fault mode" and the implementation of the PWM in the device-specific datasheet. 7

8 5. Extra Information For extra information, see Extra Information for Analog Comparator Controller. This includes: Acronyms Dependencies Errata Module History 8

9 6. Examples For a list of examples related to this driver, see Examples for Analog Comparator Controller. 9

10 7. API Overview 7.1. Macro Definitions Hysteresis Levels Refer to the "Analog Comparator Characteristics" table in the "Electrical Characteristics" chapter of the device-specific datasheet Macro ACC_ACR_HYST_0mv_max #define ACC_ACR_HYST_0mv_max Macro ACC_ACR_HYST_50mv_max #define ACC_ACR_HYST_50mv_max Macro ACC_ACR_HYST_90mv_max #define ACC_ACR_HYST_90mv_max 7.2. Function Definitions Function acc_disable() Disable the ACC module. void acc_disable( Acc * p_acc) Table 7-1 Parameters Data direction Parameter name [in, out] p_acc Module hardware register base address pointer Function acc_disable_interrupt() Disable the ACC comparison edge interrupt. void acc_disable_interrupt( Acc * p_acc) Table 7-2 Parameters Data direction Parameter name [out] p_acc Module hardware register base address pointer 10

11 Function acc_enable() Enable the ACC module. void acc_enable( Acc * p_acc) Table 7-3 Parameters Data direction Parameter name [in, out] p_acc Module hardware register base address pointer Function acc_enable_interrupt() Enable the ACC comparison edge interrupt. void acc_enable_interrupt( Acc * p_acc) Table 7-4 Parameters Data direction Parameter name [out] p_acc Module hardware register base address pointer Function acc_get_comparison_result() Get the ACC comparison result. uint32_t acc_get_comparison_result( Acc * p_acc) Table 7-5 Parameters Data direction Parameter name [in] p_acc Module hardware register base address pointer Returns The ACC comparison result. Table 7-6 Return Values Return value 0 Comparator minus input is greater than its plus input (inn>inp) 1 Comparator plus input is greater than its minus input (inp>inn) Function acc_get_interrupt_status() Get the ACC comparison edge interrupt status. uint32_t acc_get_interrupt_status( Acc * p_acc) 11

12 Table 7-7 Parameters Data direction Parameter name [in] p_acc Module hardware register base address pointer Returns The ACC comparison edge interrupt status Function acc_get_writeprotect_status() Get the ACC register write-protection status. uint32_t acc_get_writeprotect_status( Acc * p_acc) Table 7-8 Parameters Data direction Parameter name [in] p_acc Module hardware register base address pointer Returns The ACC register write-protection status. Table 7-9 Return Values Return value 0 No write-protection error ACC_WPSR_WPROTERR Write-protection error Function acc_init() Initialize the ACC module. void acc_init( Acc * p_acc, uint32_t ul_select_plus, uint32_t ul_select_minus, uint32_t ul_edge_type, uint32_t ul_invert) Note: This function performs a software reset on the ACC module prior to its initialization. Table 7-10 Parameters Data direction Parameter name [in, out] p_acc Module hardware register base address pointer [in] ul_select_plus Selection for the plus comparator input (inp) [in] ul_select_minus Selection for the minus comparator input (inn) 12

13 Data direction Parameter name [in] ul_edge_type Comparison flag triggering mode [in] ul_invert Invert the comparator output mode Where the input parameter ul_select_plus is one of the following: Parameter Value ACC_MR_SELPLUS_AD0 ACC_MR_SELPLUS_AD1 ACC_MR_SELPLUS_AD2 ACC_MR_SELPLUS_AD3 ACC_MR_SELPLUS_AD4 ACC_MR_SELPLUS_AD5 ACC_MR_SELPLUS_AD6 ACC_MR_SELPLUS_AD7 Select AD0 as the plus input Select AD1 as the plus input Select AD2 as the plus input Select AD3 as the plus input Select AD4 as the plus input Select AD5 as the plus input Select AD6 as the plus input Select AD7 as the plus input Where the input parameter ul_select_minus is one of the following: Parameter Value ACC_MR_SELMINUS_TS ACC_MR_SELMINUS_ADVREF ACC_MR_SELMINUS_DAC0 ACC_MR_SELMINUS_DAC1 ACC_MR_SELMINUS_AD0 ACC_MR_SELMINUS_AD1 ACC_MR_SELMINUS_AD2 ACC_MR_SELMINUS_AD3 Select TS as the minus input Select ADVREF as the minus input Select DAC0 as the minus input Select DAC1 as the minus input Select AD0 as the minus input Select AD1 as the minus input Select AD2 as the minus input Select AD3 as the minus input Where the input parameter ul_edge_type is one of the following: Parameter Value ACC_MR_EDGETYP_RISING ACC_MR_EDGETYP_FALLING ACC_MR_EDGETYP_ANY Rising edge of comparator output Falling edge of comparator output Any edge of comparator output 13

14 Where the input parameter ul_invert is one of the following: Parameter Value ACC_MR_INV_DIS ACC_MR_INV_EN Comparator output is directly processed Comparator output is inverted prior to being processed Function acc_reset() Software reset the ACC module. void acc_reset( Acc * p_acc) Table 7-11 Parameters Data direction Parameter name [out] p_acc Module hardware register base address pointer Function acc_set_input() Set the ACC comparator plus/minus input sources. void acc_set_input( Acc * p_acc, uint32_t ul_select_minus, uint32_t ul_select_plus) Table 7-12 Parameters Data direction Parameter name [in, out] p_acc Module hardware register base address pointer [in] ul_select_minus Selection for the minus comparator input (inn) [in] ul_select_plus Selection for the plus comparator input (inp) Where the input parameter ul_select_minus is one of the following: Parameter Value ACC_MR_SELMINUS_TS ACC_MR_SELMINUS_ADVREF ACC_MR_SELMINUS_DAC0 ACC_MR_SELMINUS_DAC1 ACC_MR_SELMINUS_AD0 ACC_MR_SELMINUS_AD1 Select TS as the minus input Select ADVREF as the minus input Select DAC0 as the minus input Select DAC1 as the minus input Select AD0 as the minus input Select AD1 as the minus input 14

15 Parameter Value ACC_MR_SELMINUS_AD2 ACC_MR_SELMINUS_AD3 Select AD2 as the minus input Select AD3 as the minus input Where the input parameter ul_select_plus is one of the following: Parameter Value ACC_MR_SELPLUS_AD0 ACC_MR_SELPLUS_AD1 ACC_MR_SELPLUS_AD2 ACC_MR_SELPLUS_AD3 ACC_MR_SELPLUS_AD4 ACC_MR_SELPLUS_AD5 ACC_MR_SELPLUS_AD6 ACC_MR_SELPLUS_AD7 Select AD0 as the plus input Select AD1 as the plus input Select AD2 as the plus input Select AD3 as the plus input Select AD4 as the plus input Select AD5 as the plus input Select AD6 as the plus input Select AD7 as the plus input Function acc_set_output() Set the ACC output. void acc_set_output( Acc * p_acc, uint32_t ul_invert, uint32_t ul_fault_enable, uint32_t ul_fault_source) Table 7-13 Parameters Data direction Parameter name [in, out] p_acc Module hardware register base address pointer [in] ul_invert Invert comparator output [in] ul_fault_enable Fault enable [in] ul_fault_source Selection of fault source Where the input parameter ul_invert is one of the following: Parameter Value ACC_MR_INV_DIS ACC_MR_INV_EN Comparator output is directly processed Comparator output is inverted prior to being processed Where the input parameter ul_fault_enable is one of the following: 15

16 Parameter Value ACC_MR_FE_DIS The FAULT output is tied to 0 ACC_MR_FE_EN The FAULT output is driven by ul_fault_source Where the input parameter ul_fault_source is one of the following: Parameter Value ACC_MR_SELFS_CF The CF flag is used to drive the FAULT output ACC_MR_SELFS_OUTPUT The output of the Analog Comparator flag is used to drive the FAULT output Function acc_set_writeprotect() Set the ACC register write-protection. void acc_set_writeprotect( Acc * p_acc, uint32_t ul_enable) Table 7-14 Parameters Data direction Parameter name [out] p_acc Module hardware register base address pointer [in] ul_enable 1 to enable, 0 to disable 16

17 8. Extra Information for Analog Comparator Controller 8.1. Acronyms Below is a table listing the acronyms used in this module, along with their intended meanings. Acronym AD DAC GPIO NVIC PMC PWM QSG Definition Analog to Digital Digital to Analog Converter General Purpose Input Output Nested Vectored Interrupt Controller Power Management Controller Pulse Width Modulator Quick Start Guide 8.2. Dependencies This driver has the following dependencies: None 8.3. Errata There are no errata related to this driver Module History An overview of the module history is presented in the table below, with details on the enhancements and fixes made to the module since its first release. The current version of this corresponds to the newest version in the table. Changelog Initial document release 17

18 9. Examples for Analog Comparator Controller This is a list of the available Quick Start guides (QSGs) and example applications for SAM3S/4E/4S Analog Comparator Controller (ACC) Driver. QSGs are simple examples, with step-by-step instructions to configure and use this driver in a selection of use cases. Note that a QSG can be compiled as a standalone application or be added to the user application. Quick Start Guide for the ACC driver Analog Comparator Controller - Example Interrupt Event Generation 9.1. Quick Start Guide for the ACC driver This is the quick start guide for the SAM3S/4E/4S Analog Comparator Controller (ACC) Driver, with stepby-step instructions on how to configure and use the driver for a specific use case. The code examples can be copied into e.g. the main application loop or any other function that will need to control the ACC module Use Cases ACC Basic Usage ACC Basic Usage This use case will demonstrate how to initialize the ACC module in interrupt mode Setup Steps Prerequisites This module requires the following service: Setup Code System Clock Management (sysclock) Add this to your main application C-file: void ACC_Handler(void) { } Add this to the main loop or a setup function: pmc_enable_periph_clk(id_acc); Workflow 1. Initialize the ACC module so that: ADC channel 5 is connected to its positive input DAC channel 0 is connected to its negative input Generate an interrupt on either edge of the output Disable the ACC module output inversion acc_init(acc, ACC_MR_SELPLUS_AD5, ACC_MR_SELMINUS_DAC0, ACC_MR_EDGETYP_ANY, ACC_MR_INV_DIS); 18

19 2. Enable the ACC module interrupt: NVIC_EnableIRQ(ACC_IRQn); acc_enable_interrupt(acc); Usage Steps Usage Code In the ACC_Handler() function, check if the output result is available by: if ((ul_status & ACC_ISR_CE) == ACC_ISR_CE) { } In the ACC_Handler() function, check if ADC channel 5 is greater than DAC channel 0 by: if (acc_get_comparison_result(acc)) { do_something_with_a_greater_result(); } In the ACC_Handler() function, check if ADC channel 5 is less than DAC channel 0 by: if (!acc_get_comparison_result(acc)) { do_something_with_a_lesser_result(); } 9.2. Analog Comparator Controller - Example Interrupt Event Generation Purpose This example demonstrates how to use the ACC driver to perform a voltage comparison on a pair of inputs and generate an interrupt Requirements This example can be used on the following evaluation kits: SAM4S EK SAM4S EK The DAC0 and AD5 signals are selected as the inputs to the analog comparator. The user can change the output voltage of DAC0 and also change the voltage on AD5 by adjusting VR1 on the evaluation kit. The DAC0 output voltage can be adjusted between (1/6)*ADVREF and (5/6)*ADVREF in software, whilst the input voltage on AD5 can vary between 0 and ADVREF. A comparison interrupt event is generated when the input voltages are no longer equal Main Files acc.c: Analog Comparator Controller driver acc.h: Analog Comparator Controller driver header file acc_example.c: Analog Comparator Controller example application 19

20 Compilation Information Usage This software is written for GNU GCC and IAR Embedded Workbench for Atmel. Other compilers may or may not work. 1. Build the program and download it into the evaluation board. 2. On the computer, open, and configure a terminal application (e.g., HyperTerminal on Microsoft Windows ) with these settings: baud 8 bits of data No parity 1 stop bit No flow control 3. Start the application. 4. In the terminal window, the following text should appear: -- ACC IRQ Example xxx xxxxxx-xx -- Compiled: xxx xx xxxx xx:xx:xx Menu Choices for this example-- -- s: Set new DAC0 output voltage v: Get voltage on potentiometer m: Display this menu again Enter a character on the terminal to select a menu option. 6. Change the voltage on AD5 by adjusting VR1 on the evaluation kit in order. To see what comparison events occur. 20

21 10. Document Revision History Doc. Rev. Date Comments 42292B 07/2015 Updated title of application note and added list of supported devices 42292A 05/2014 Initial document release 21

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