你不知道也不會怎樣的關於pinMode的奇淫巧技
呼叫函式如digitalRead或analogWrite時，難道不就決定這個pin是用來INPUT或OUTPUT了嗎，那在pinMode宣告的意義為何呢?
這是個人筆記 沒有深入淺出 不會旁徵博引 只有很多隨著思考方向跳出的補充內容
- 你可以digitalRead一個OUTPUT的pin
/code/
The panoramic view of the VR experience study, including weapons, monsters, and turrets.
• Participants use each weapon in a controlled sequence, interacting with monsters that appear one at a time or hitting tennis balls shot from turrets.
• This setup provided a vivid, comprehensive gauge of how dynamic PAF and force direction can significantly enhance realism and immersion in virtual environments. The careful calibration and design of VR interactions based on realistic haptic feedback models were central to achieving this advanced level of user experience.
上面這段程式劈頭就宣告了digital pin 13為OUTPUT，竟又在最後恬不知恥的以其呼叫digitalRead，OUTPUT和read in這兩者不應該是矛盾的嗎？
Yes im OUTPUT, yes I read in, we exist.
要解答這個問題，還得先從arduino的晶片講起。
不失一般姓，以arduino uno 為例
Uno使用的是ATmega328P 一個8bit 的avr晶片
The panoramic view of the VR experience study, including weapons, monsters, and turrets.
• Participants use each weapon in a controlled sequence, interacting with monsters that appear one at a time or hitting tennis balls shot from turrets.
• This setup provided a vivid, comprehensive gauge of how dynamic PAF and force direction can significantly enhance realism and immersion in virtual environments. The careful calibration and design of VR interactions based on realistic haptic feedback models were central to achieving this advanced level of user experience.
The panoramic view of the VR experience study, including weapons, monsters, and turrets.
• Participants use each weapon in a controlled sequence, interacting with monsters that appear one at a time or hitting tennis balls shot from turrets.
• This setup provided a vivid, comprehensive gauge of how dynamic PAF and force direction can significantly enhance realism and immersion in virtual environments. The careful calibration and design of VR interactions based on realistic haptic feedback models were central to achieving this advanced level of user experience.
AVR 晶片上的每個 port-line 都受三個暫存器控制，分別是 (x 代表 B, C, D):
B: 對應 Arduino 的 Digital pin 8 to 13
C: 對應 Arduino 的 Analog input pin 0 to 5
D: 對應 Arduino 的 Digital pins 0 to 7
- DDRx 暫存器: 用來控制pin是 INPUT 或 OUTPUT。
- PORTx 暫存器: Port-B Register (PBR)
用來控制OUTPUT pin的輸出訊號為 HIGH 或 LOW
- PINx 暫存器: 唯讀，用來讀取INPUT pin的輸入訊號
舉例來說，pin13對應到PORTB的第一個bit，bit1，所以也叫做PB1。
每個pin對應的暫存器可以參考schemic
(UNO Schemic https://www.arduino.cc/en/uploads/Main/arduino-uno-schematic.pdf)
實際上，當你拿某個OUTPUT的pin 來執行digitalRead的函式時，你會讀取一個叫做PORTx的暫存器裡面某一個bit的值，而這個值則代表了這個OUTPUT pin現在的輸出狀態，也就是HIGH或LOW。
再看看上面這段程式，每秒鐘讀取一次pin13的狀態，接著寫入一個與其reverse的狀態，所以達到在每秒之間交替寫入0跟1(也就是HIGH跟LOW)的效果，也就是你能夠用一行程式就完成arduino 101 — blink。
當然你也可以 digitalwrite 一個 input pin
這時你在write的是pullup 也就是跟pinMode() to INPUT_PULLUP一樣
(https://www.arduino.cc/reference/en/language/functions/digital-io/digitalwrite/)
turns on or off the internal pull-up resistor
＃pull up 是甚麼…
Writing high will pretty reliably make it read high unless the pin is connected to ground some other way. Writing low to it will leave it floating and it will read whatever noise it picks up. If it was previously written high it will probably stay that way for a bit.
所以當你呼叫函釋digitalREAD/ digitalWtrite時 這個腳為是Input跟outout都有可能的，因此需要pinmode。
那如果是analog腳為呢
因為analogwrite
Analogread
Source code
https://github.com/arduino/ArduinoCore-avr/blob/master/cores/arduino/wiring_analog.c
所以他們只有在 是合理的
Output digitalREAd digitalwrite analogwrite
Input digitalread digitalwrite analogread
最後整理
Arduino 在通電時 所有腳位都會設定成Input 所以其實digital的input都不用先宣告。
(除了中間要將output腳為轉成input使用)
必須、非得用pinmode: digital output analogwrite會自動
可用 可不用 digital INPUT or analog OUTPUT (PWM) analogread
Pin 14-19
Analog腳為怎麼當成digital來用哩
表格
而要使用digitalwrite 就要先宣告是output了
這時就會當成gpio來使用
https://www.arduino.cc/en/Tutorial/Foundations/AnalogInputPins
補充 and 部分
analog需要Pinmode的特例
需要注意的是 如果中間需要轉換成input 讀取analog數值，那這時候就需要pinmode 轉乘input了 舉例來說
pinMode(A3, OUTPUT);
digitalWrite(A3, LOW);
// other stuff
iResult = analogRead (A3) ;
這時你的analog只會讀取到low 而不是正確的數值。
總結來說 analog需要使用pinmode的時機就是Setting the mode of that same pin AS A DIGITAL PIN is possible, and, when switching from analog to digital mode, or from digital mode to analog mode, required.
Tx
Rx
可用來replace usb 或連接兩個版子 或藍芽模組
Tx to rx
Rx to tx
Vin 根外接電源一樣 6v以上
Reset 跟 reset 按鈕一樣
Pwm on any pin
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