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Example_Touchpads/ADB_Trackball.ino

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+/* 
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+       http://www.apache.org/licenses/LICENSE-2.0
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+// This software implements an Apple ADB interface for a trackball. It uses a  
+// Teensy 3.2 and is based on the code from this Imgur post https://imgur.com/a/BQjt9le
+// 
+// Revision History
+// Initial Release Aug 3, 2021
+// 
+#define ADB_DATA_PIN 5 // TB bidirectional data pin
+//
+// TB Constants
+int ADB_TIMEOUT = 10000;
+// TB Functions
+static void send_0bit() {
+ digitalWrite(ADB_DATA_PIN, LOW);
+ delayMicroseconds(65);
+ digitalWrite(ADB_DATA_PIN, HIGH);
+ delayMicroseconds(35);
+}
+
+static void send_1bit() {
+ digitalWrite(ADB_DATA_PIN, LOW);
+ delayMicroseconds(35);
+ digitalWrite(ADB_DATA_PIN, HIGH);
+ delayMicroseconds(65);
+}
+
+static void attn() {
+  //delay(1);
+  digitalWrite(ADB_DATA_PIN, LOW);
+  delayMicroseconds(800-35);
+  send_0bit();
+}
+
+void send_talk_command() {
+ //attn
+ pinMode(ADB_DATA_PIN, OUTPUT);
+ attn();
+ //address (3) 0011
+ //0
+  send_0bit();
+  send_0bit();
+  send_1bit();
+  send_1bit();
+ //talk 11
+  send_1bit();
+  send_1bit();
+ //register 00
+  send_0bit();
+  send_0bit();
+ //stop bit
+  send_0bit();
+ //start to stop time
+ delayMicroseconds(140);
+
+}
+int receive_data_packet() {
+ pinMode(ADB_DATA_PIN, INPUT);
+ int data_time = 0;
+ bool command_stop = false;
+ int adb_data = 0;
+ //begin reading ADB datapin
+ 
+ while(digitalRead(ADB_DATA_PIN)!=LOW && data_time < ADB_TIMEOUT){
+  //wait for beginning of start bit
+  data_time+=1;
+  delayMicroseconds(1);
+ }
+
+  while(digitalRead(ADB_DATA_PIN)!=HIGH && data_time < ADB_TIMEOUT){
+  //wait for end of start bit
+  data_time+=1;
+  delayMicroseconds(1);
+ }
+
+ while(digitalRead(ADB_DATA_PIN)!=LOW && data_time < ADB_TIMEOUT){
+  //wait for beginning of first data bit
+  data_time+=1;
+  delayMicroseconds(1);
+ }
+
+ //data packet
+ data_time = 0;
+ while(!command_stop && data_time < ADB_TIMEOUT) {
+  int low = 0;
+  int high = 0;
+  bool bit_stop = false;
+  while(!bit_stop && data_time < ADB_TIMEOUT) {
+    
+    int adb_stream = digitalRead(ADB_DATA_PIN);
+    if(adb_stream == LOW) low+=1;
+    if(adb_stream == HIGH) high+=1;
+    if(adb_stream == LOW && high > 0) bit_stop = true;
+    if(high > 240){
+      bit_stop = true;
+      break;
+    }
+    data_time+=1;
+    delayMicroseconds(1);
+  }
+  if(high > 240){
+    command_stop = true;
+  }
+  //append the new data bit to adb_data
+  if(high > low && !command_stop) adb_data = (adb_data << 1) + 1;
+  if(low > high && !command_stop) adb_data = adb_data << 1;
+  
+ }
+ //stop bit 
+ return adb_data;
+}
+
+void parse_data(int data) {
+      if(data !=0) {
+       int mousex = data & 0b0000000001111111;
+       int mousey = (data >> 8) & 0b01111111;
+       //the mouse value is
+        //7 bit two's complement
+       if((mousey & 0b1000000) != 0) {
+          mousey =  ((~mousey + 1) & 0b01111111) * -1;
+       }
+       if((mousex & 0b1000000) != 0) {
+          mousex =  ((~mousex + 1) & 0b01111111) * -1;
+       }
+       Mouse.move(mousex, mousey);
+       Mouse.move(mousex, mousey);
+
+      int mouseClick = data & 0b1000000000000000;
+      
+      if(mouseClick == 0) {
+        Mouse.set_buttons(1,0,0);
+      }
+      else if(mouseClick != 0) {
+        Mouse.set_buttons(0,0,0);
+      }
+     }
+}
+
+//
+//----------------------------------Setup-------------------------------------------
+void setup() {
+  
+}
+//
+//---------------------------------Main Loop---------------------------------------------
+//
+void loop() {   
+   send_talk_command();
+   parse_data(receive_data_packet());
+//
+  delay(20); // 
+}