61 lines
2.4 KiB
C++
61 lines
2.4 KiB
C++
#ifndef ROWSCANNER_SHIFTREGSREADSTROBED_H
|
|
#define ROWSCANNER_SHIFTREGSREADSTROBED_H
|
|
|
|
#include <Arduino.h>
|
|
#include <inttypes.h>
|
|
#include <config_keybrd.h>
|
|
#include <SPI.h>
|
|
#include <ScannerInterface.h>
|
|
|
|
/* Scanner_ShiftRegsReadStrobed reads shift registers.
|
|
Shift registers can be daisy chained for a total of 32 read pins.
|
|
This was tested on 74HC165 shift registers, which are Parallel-In-Serial-Out (PISO).
|
|
|
|
The class works with machanical switches or photointerrupter switches.
|
|
A "strobe" powers the IR LEDs for a short time while the shift registers read the photo transistors.
|
|
The IR LEDs are off most of the time to preserve IR LED life.
|
|
|
|
Example instantiation:
|
|
Scanner_ShiftRegsReadStrobed scanner_R(HIGH, 6, 4);
|
|
|
|
There are three Scanner_ShiftRegsReadStrobed parameters.
|
|
1. "activeState" paramter is active state HIGH or LOW.
|
|
2. "slaveSelect" paramter is controller pin connected to shift register's SHIFT-LOAD pin.
|
|
3. "byte_count" is the number of bytes to read from shift registers (1 to 4).
|
|
byte_count should cover all the row's keys: byte_count*8 >= row's keyCount
|
|
|
|
Hardware setup:
|
|
Each row of keys is connected to a controller by 6 wires:
|
|
* GND
|
|
* power
|
|
* CLK
|
|
* Slave Select
|
|
* MISO
|
|
* strobe
|
|
|
|
For active low:
|
|
Shift-register parallel-input pins need 10k Ohm pull-up resistors powered.
|
|
Orient diodes with cathode (banded end) towards the write pins (row)
|
|
Controller's MISO pin is connected to shift register's complementary serial output (/QH) pin
|
|
|
|
For active high:
|
|
Shift-register parallel-input pins need 10k pull-down resistors grounded.
|
|
Orient diodes with cathode (banded end) towards the read pins.
|
|
Controller's MISO pin is connected to shift register's serial output (QH) pin
|
|
|
|
If multiple rows (or any SPI divice) share a MISO line, the shift registers need to be isolated by a tri-state buffer chip.
|
|
*/
|
|
class Scanner_ShiftRegsReadStrobed : public ScannerInterface
|
|
{
|
|
private:
|
|
const bool activeState; //logic level of strobe on, active state HIGH or LOW
|
|
const uint8_t slaveSelect;//controller pin number connected to shift register SHIFT-LOAD pin
|
|
const uint8_t byte_count; //number of bytes to read from shift registers
|
|
public:
|
|
Scanner_ShiftRegsReadStrobed(const bool activeState,
|
|
const uint8_t slaveSelect, const uint8_t byte_count);
|
|
virtual void init(const uint8_t strobePin);
|
|
virtual read_pins_t scan(const uint8_t strobePin);
|
|
};
|
|
#endif
|