203 lines
7.9 KiB
C
203 lines
7.9 KiB
C
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// ---------------------------------------------------------------------------
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// Created/Adapted by Bill Perry 2012-03-16
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// Copyright 2012 - Under creative commons license 3.0:
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// Attribution-ShareAlike CC BY-SA
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//
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// This software is furnished "as is", without technical support, and with no
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// warranty, express or implied, as to its usefulness for any purpose.
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//
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// @file LiquidCrystal_SR2W.h
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// Connects a hd44780 LCD using 2 pins from the Arduino, via an 8-bit
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// ShiftRegister (SR2W from now on).
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//
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// @brief
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// This is the 2 wire shift register interface class for the LCD library
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//
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// The functionality provided by this class and its base class is a superset of
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// the original functionality of the Arduino LiquidCrystal library and can
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// be used as such.
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// See the LCD class for a full description of the API functions available.
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//
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// It works with a 8-bit unlatched, no-tristate, unidirectional SIPO (Serial-In-Parallel-Out)
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// shift register (IE a very simple SR), and an hd44780 LCD in 4-bit mode.
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// Any such shift register should do (pref. 74LS family IC's for 2-wire).
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// 74LS164 and 74HC595 have been exstensively tested.
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//
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//
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// 2 Pins required from the Arduino:
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// - Data/Enable
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// - Clock
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// The Data pin is also used to control the enable signal
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// LCD RW-pin hardwired to LOW (only writing to LCD).
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// Busy Flag (BF, data bit D7) is not read.
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//
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// Original project homepage: http://code.google.com/p/arduinoshiftreglcd/
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//
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// Shift register bits
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// Bit #0 - (cannot be used on 74HC595)
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// Bit #1 - optional backlight control
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// Bit #2 - connects to RS (Register Select) on the LCD
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// Bit #3 - connects to LCD data inputs D4
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// Bit #4 - connects to LCD data inputs D5
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// Bit #5 - connects to LCD data inputs D6
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// Bit #6 - connects to LCD data inputs D7
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// Bit #7 - enables the LCD enable-puls (via the diode-resistor AND "gate")
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//
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// Wiring for a 74LS164
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// ---------------------
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// 1k/4.7k
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// +--------[ Resistor ]--------+---(LCD Enable)
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// | |
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// | 74LS164 (VCC) |
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// | +----u----+ | _V_ diode
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// (data pin)---+---+--1-|A VCC|-14-+ |
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// | | | |
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// +--2-|B Q7|-13------+
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// 3-|Q0 Q6|-12--(LCD D7)
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// (BL Circuit)--------4-|Q1 Q5|-11--(LCD D6)
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// (LCD RS)------------5-|Q2 Q4|-10--(LCD D5)
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// (LCD D4)------------6-|Q3 /MR|--9--(VCC)
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// +-7-|GND CP|--8--(clock pin)
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// | +---------+
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// | 0.1uf
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// (gnd)-----||----(vcc)
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//
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// Wiring for a 74HC595
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// --------------------
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// NOTE: the 74HC595 is a latching shift register. In order to get it to operate
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// in a "non latching" mode, RCLK and SCLK are tied together. The side effect of this
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// is that the latched output is one clock behind behind the internal shift register bits.
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// To compensate for this the wiring is offset by one bit position lower.
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// For example, while the backlight is hooked to Q0 it is still using bit 1 of
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// of the shift register because the outputs are 1 clock behind the real internal shift
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// register.
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//
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// 74HC595 (VCC)
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// +----u----+ | +-----------------------(BL circuit)
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// (LCD RS)------------1-|Q1 VCC|-16-+ | +--------------------(data pin)
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// (LCD D4)------------2-|Q2 Q0|-15----+ | 1k/4.7k
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// (LCD D5)------------3-|Q3 SER|-14-------+---[ Resistor ]--+--(LCD Enable)
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// (LCD D6)------------4-|Q4 /OE|-13--(gnd) |
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// (LCD D7)------------5-|Q5 RCLK|-12-------+ |
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// | | | |
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// +------6-|Q6 SCLK|-11-------+--(clock pin) |
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// | 7-|Q7 /MR|-10--(VCC) |
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// | +-8-|GND Q6'|--9 |
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// | | +---------+ diode _V_
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// | | 0.1uf |
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// | (gnd)-----||----(vcc) |
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// +-----------------------------------------------+
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//
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//
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// Backlight Control circuit
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// -------------------------
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// Because the shift resiter is not latching the outputs, the backlight circuitry
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// will "see" the output bits as they are shifted into the shift register which
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// can cause the backlight to flicker rather than remain constantly on/off.
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// The circuit below slows down the transitions to the transistor to remove
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// the visible flicker. When the BL input is HIGH the LCD backlight will turn on.
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//
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// (value depends on LCD, 100ohm is usually safe)
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// (LCD BL anode)---[ resistor ]---(vcc)
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//
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// (LCD BL cathode)-------------------------------+
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// |
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// D
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// |
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// (BL input)----[ 4.7k Resistor ]----+-------G-|-< (2N7000 FET)
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// | |
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// (0.1uf) = S
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// | |
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// (gnd) (gnd)
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//
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//
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//
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//
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// History
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// 2012.03.16 bperrybap - creation/adaption from SR header to create SR2W header.
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// Fixed typo in SR2W mask define names
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// @author B. Perry - bperrybap@opensource.billsworld.billandterrie.com
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// --------------------------------------------------------------------------------
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#ifndef _LIQUIDCRYSTAL_SR2W_
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#define _LIQUIDCRYSTAL_SR2W_
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#include <inttypes.h>
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#include "LCD.h"
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#include "FastIO.h"
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// two-wire SR output bit constants
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// ---------------------------------------------------------------------------
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#define SR2W_BL_MASK 0x02
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#define SR2W_RS_MASK 0x04
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#define SR2W_DATA_MASK 0x78 // data bits are hard coded to be SR bits 6,5,4,3
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#define SR2W_EN_MASK 0x80 // cannot ever be changed
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class LiquidCrystal_SR2W : public LCD
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{
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public:
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/*!
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@method
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@abstract LCD 2 wire SHIFT REGISTER constructor.
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@discussion Defines the pin assignments that connect to the shift register.
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The constructor does not initialize the LCD. Assuming 1 line 8 pixel high
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font.
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@param srdata[in] Arduino pin for shift register data line.
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@param srclock[in] Arduino pin for shift register clock line.
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@param blpol[in] optional backlight polarity (default = POSITIVE)
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*/
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LiquidCrystal_SR2W (uint8_t srdata, uint8_t srclock, t_backlighPol blpol = POSITIVE);
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/*!
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@function
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@abstract Send a particular value to the LCD.
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@discussion Sends a particular value to the LCD for writing to the LCD or
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as an LCD command using the shift register.
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Users should never call this method.
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@param value[in] Value to send to the LCD.
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@param mode[in] DATA=8bit data, COMMAND=8bit cmd, FOUR_BITS=4bit cmd
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the LCD.
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*/
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virtual void send(uint8_t value, uint8_t mode);
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/*!
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@function
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@abstract Switch-on/off the LCD backlight.
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@discussion Switch-on/off the LCD backlight.
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The setBacklightPin has to be called before setting the backlight for
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this method to work. @see setBacklightPin.
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@param mode[in] backlight mode (0 off, non-zero on)
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*/
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void setBacklight ( uint8_t mode );
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private:
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/*!
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@method
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@abstract Initializes the LCD pin allocation
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@discussion Initializes the LCD pin allocation and configuration.
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*/
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void init ( uint8_t srdata, uint8_t srclock, t_backlighPol blpol, uint8_t lines, uint8_t font );
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/*!
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* @method
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* @abstract takes care of shifting and the enable pulse
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*/
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void loadSR (uint8_t val);
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fio_register _srDataRegister; // Serial Data pin
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fio_bit _srDataMask;
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fio_register _srClockRegister; // Clock Pin
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fio_bit _srClockMask;
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uint8_t _blPolarity;
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uint8_t _blMask;
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};
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#endif
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