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Example_Touchpads/Touchpad_LC.ino
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Example_Touchpads/Touchpad_LC.ino
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/* Copyright 2019 Frank Adams
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// This software interfaces the Teensy LC with the 3.3v PS/2 touchpad found in an HP DV9000 laptop.
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// WARNING: THE TEENSY LC NEEDS CLOCK AND DATA LEVEL TRANSLATORS TO INTERFACE WITH A 5V TOUCHPAD.
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// The ps/2 code uses the USB PJRC Mouse functions at www.pjrc.com/teensy/td_mouse.html
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// The ps/2 code has a watchdog timer so the code can't hang if a clock edge is missed.
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// In the Arduino IDE, select Tools, Teensy LC. Also under Tools, select Keyboard+Mouse+Joystick
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//
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// Revision History
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// Rev 1.0 - Nov 23, 2018 - Original Release
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// Rev 1.1 - Dec 2, 2018 - Replaced ps/2 trackpoint code from playground arduino with my own code
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// Rev 1.2 - Feb 2, 2019 - Changed the error routine and added an error LED
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// Rev 1.3 - Feb 14, 2019 - Changed the comments and I/O pins for the Teensy LC
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//
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// This code has been tested on the touchpad from an HP DV9000 touchpad
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// Touchpad part number 920-000702-04 Rev A
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// The test points on the touchpad were wired as follows:
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// T22 = 3.3V
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// T23 = Gnd (I soldered to the ground plane)
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// T10 = Clock
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// T11 = Data
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// This touchpad has active pullups so no additional pullups were required.
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//
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// The touchpad ps/2 data and clock lines are connected to the following Teensy I/O pins
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#define TP_DATA 20 // modify these I/O's to match your jumpers
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#define TP_CLK 18
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// Teensy LED will be lit if the touchpad fails to respond properly during initialization
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#define ERROR_LED 13
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//
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// Declare variable that will be used by functions
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boolean touchpad_error = LOW; // sent high when touch pad routine times out
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//
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// Function to set a pin to high impedance (acts like open drain output)
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void go_z(int pin)
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{
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pinMode(pin, INPUT);
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digitalWrite(pin, HIGH);
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}
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//
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// Function to set a pin as an input with a pullup
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void go_pu(int pin)
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{
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pinMode(pin, INPUT_PULLUP);
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digitalWrite(pin, HIGH);
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}
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//
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// Function to send a pin to a logic low
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void go_0(int pin)
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{
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pinMode(pin, OUTPUT);
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digitalWrite(pin, LOW);
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}
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//
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// Function to send a pin to a logic high
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void go_1(int pin)
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{
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pinMode(pin, OUTPUT);
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digitalWrite(pin, HIGH);
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}
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//
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// *****************Functions for Touchpad***************************
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//
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// Function to send the touchpad a byte of data (command)
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//
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void tp_write(char send_data)
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{
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unsigned int timeout = 200; // breakout of loop if over this value in msec
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elapsedMillis watchdog; // zero the watchdog timer clock
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char odd_parity = 0; // clear parity bit count
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// Enable the bus by floating the clock and data
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go_pu(TP_CLK); //
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go_pu(TP_DATA); //
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delayMicroseconds(250); // wait before requesting the bus
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go_0(TP_CLK); // Send the Clock line low to request to transmit data
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delayMicroseconds(100); // wait for 100 microseconds per bus spec
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go_0(TP_DATA); // Send the Data line low (the start bit)
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delayMicroseconds(1); //
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go_pu(TP_CLK); // Release the Clock line so it is pulled high
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delayMicroseconds(1); // give some time to let the clock line go high
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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// send the 8 bits of send_data
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for (int j=0; j<8; j++) {
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if (send_data & 1) { //check if lsb is set
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go_pu(TP_DATA); // send a 1 to TP
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odd_parity = odd_parity + 1; // keep running total of 1's sent
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}
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else {
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go_0(TP_DATA); // send a 0 to TP
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}
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == LOW) { // loop until the clock goes high
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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send_data = send_data >> 1; // shift data right by 1 to prepare for next loop
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}
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// send the parity bit
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if (odd_parity & 1) { //check if lsb of parity is set
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go_0(TP_DATA); // already odd so send a 0 to TP
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}
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else {
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go_pu(TP_DATA); // send a 1 to TP to make parity odd
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}
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == LOW) { // loop until the clock goes high
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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go_pu(TP_DATA); // Release the Data line so it goes high as the stop bit
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delayMicroseconds(80); // testing shows delay at least 40us
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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delayMicroseconds(1); // wait to let the data settle
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if (digitalRead(TP_DATA)) { // Ack bit s/b low if good transfer
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}
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while ((digitalRead(TP_CLK) == LOW) || (digitalRead(TP_DATA) == LOW)) { // loop if clock or data are low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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// Inhibit the bus so the tp only talks when we're listening
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go_0(TP_CLK);
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}
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//
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// Function to get a byte of data from the touchpad
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//
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char tp_read(void)
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{
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unsigned int timeout = 200; // breakout of loop if over this value in msec
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elapsedMillis watchdog; // zero the watchdog timer clock
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char rcv_data = 0; // initialize to zero
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char mask = 1; // shift a 1 across the 8 bits to select where to load the data
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char rcv_parity = 0; // count the ones received
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go_pu(TP_CLK); // release the clock
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go_pu(TP_DATA); // release the data
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delayMicroseconds(5); // delay to let clock go high
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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if (digitalRead(TP_DATA)) { // Start bit s/b low from tp
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// start bit not correct - put error handler here if desired
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}
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == LOW) { // loop until the clock goes high
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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for (int k=0; k<8; k++) {
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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if (digitalRead(TP_DATA)) { // check if data is high
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rcv_data = rcv_data | mask; // set the appropriate bit in the rcv data
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rcv_parity++; // increment the parity bit counter
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}
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mask = mask << 1;
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == LOW) { // loop until the clock goes high
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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}
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// receive parity
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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if (digitalRead(TP_DATA)) { // check if received parity is high
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rcv_parity++; // increment the parity bit counter
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}
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rcv_parity = rcv_parity & 1; // mask off all bits except the lsb
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if (rcv_parity == 0) { // check for bad (even) parity
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// bad parity - pass to future error handler
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}
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == LOW) { // loop until the clock goes high
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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// stop bit
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == HIGH) { // loop until the clock goes low
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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if (digitalRead(TP_DATA) == LOW) { // check if stop bit is bad (low)
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// send bad stop bit to future error handler
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}
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delayMicroseconds(1); // delay to let the clock settle out
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while (digitalRead(TP_CLK) == LOW) { // loop until the clock goes high
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if (watchdog >= timeout) { //check for infinite loop
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break; // break out of infinite loop
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}
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}
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// Inhibit the bus so the tp only talks when we're listening
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go_0(TP_CLK);
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return rcv_data; // pass the received data back
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}
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//
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void touchpad_init()
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{
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touchpad_error = LOW; // start with no error
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go_pu(TP_CLK); // float the clock and data to touchpad
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go_pu(TP_DATA);
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// Sending reset command to touchpad
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tp_write(0xff);
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if (tp_read() != 0xfa) { // verify correct ack byte
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touchpad_error = HIGH;
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}
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delay(350); // wait 350ms so tp can run its self diagnostic
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// verify proper response from tp
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if (tp_read() != 0xaa) { // verify basic assurance test passed
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touchpad_error = HIGH;
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}
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if (tp_read() != 0x00) { // verify basic assurance test passed
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touchpad_error = HIGH;
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}
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// increase resolution from 4 counts/mm to 8 counts/mm
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tp_write(0xe8); // Sending resolution command
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if (tp_read() != 0xfa) { // verify correct ack byte
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touchpad_error = HIGH;
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}
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tp_write(0x03); // value of 03 = 8 counts/mm resolution (default is 4 counts/mm)
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if (tp_read() != 0xfa) { // verify correct ack byte
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touchpad_error = HIGH;
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}
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// Sending remote mode code so the touchpad will send data only when polled
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tp_write(0xf0); // remote mode
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if (tp_read() != 0xfa) { // verify correct ack byte
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touchpad_error = HIGH;
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}
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}
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// ************************************Begin Routine*********************************************************
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void setup()
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{
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touchpad_init(); // reset touchpad, then set it's resolution and put it in remote mode
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pinMode(ERROR_LED, OUTPUT); // define teensy I/O 13 as an output
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}
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// declare and initialize variables
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char mstat; // touchpad status reg = Y overflow, X overflow, Y sign bit, X sign bit, Always 1, Middle Btn, Right Btn, Left Btn
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char mx; // touchpad x movement = 8 data bits. The sign bit is in the status register to
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// make a 9 bit 2's complement value. Left to right on the touchpad gives a positive value.
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char my; // touchpad y movement also 8 bits plus sign. Touchpad movement away from the user gives a positive value.
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boolean over_flow; // set if x or y movement values are bad due to overflow
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boolean left_button = 0; // on/off variable for left button = bit 0 of mstat
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boolean right_button = 0; // on/off variable for right button = bit 1 of mstat
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boolean old_left_button = 0; // on/off variable for left button status the previous polling cycle
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boolean old_right_button = 0; // on/off variable for right button status the previous polling cycle
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boolean button_change = 0; // Active high, shows when a touchpad left or right button has changed since last polling cycle
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// ************************************Main Loop***************************************************************
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void loop() {
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if (touchpad_error == LOW) { // check if touchpad is present
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digitalWrite(ERROR_LED, LOW); // turn off LED on Teensy to show touchpad initialized OK
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// poll the touchpad for new movement data
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over_flow = 0; // assume no overflow until status is received
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tp_write(0xeb); // request data
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if (tp_read() != 0xfa) { // verify correct ack byte
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// bad ack - pass to future error handler
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}
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mstat = tp_read(); // save into status variable
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mx = tp_read(); // save into x variable
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my = tp_read(); // save into y variable
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if (((0x80 & mstat) == 0x80) || ((0x40 & mstat) == 0x40)) { // x or y overflow bits set?
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over_flow = 1; // set the overflow flag
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}
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// change the x data from 9 bit to 8 bit 2's complement
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mx = mx & 0x7f; // mask off 8th bit
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if ((0x10 & mstat) == 0x10) { // move the sign into
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mx = 0x80 | mx; // the 8th bit position
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}
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// change the y data from 9 bit to 8 bit 2's complement and then take the 2's complement
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// because y movement on ps/2 format is opposite of touchpad.move function
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my = my & 0x7f; // mask off 8th bit
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if ((0x20 & mstat) == 0x20) { // move the sign into
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my = 0x80 | my; // the 8th bit position
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}
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my = (~my + 0x01); // change the sign of y data by taking the 2's complement (invert and add 1)
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// zero out mx and my if over_flow or touchpad_error is set
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if ((over_flow) || (touchpad_error)) {
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mx = 0x00; // data is garbage so zero it out
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my = 0x00;
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}
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// send the x and y data back via usb if either one is non-zero
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if ((mx != 0x00) || (my != 0x00)) {
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Mouse.move(mx,my);
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}
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//
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// send the touchpad left and right button status over usb if no error
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if ((0x01 & mstat) == 0x01) { // if left button set
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left_button = 1;
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}
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else { // clear left button
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left_button = 0;
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}
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if ((0x02 & mstat) == 0x02) { // if right button set
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right_button = 1;
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}
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else { // clear right button
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right_button = 0;
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}
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// Determine if the left or right touch pad buttons have changed since last polling cycle
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button_change = (left_button ^ old_left_button) | (right_button ^ old_right_button);
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// Don't send button status if there's no change since last time.
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if (button_change){
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Mouse.set_buttons(left_button, 0, right_button); // send button status
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}
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old_left_button = left_button; // remember new button status for next polling cycle
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old_right_button = right_button;
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}
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else {
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digitalWrite(ERROR_LED, HIGH);
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}
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//
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// **************************************End of touchpad routine***********************************
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//
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delay(30); // wait 30ms before repeating next polling cycle
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}
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