arduino:arduino_crash_course:misc
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arduino:arduino_crash_course:misc [2015/02/15 04:42] – mithat | arduino:arduino_crash_course:misc [2015/02/16 04:22] (current) – [Serial communication] mithat | ||
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===== Uno hardware ===== | ===== Uno hardware ===== | ||
- | Each of the 14 digital pins on the Uno can be used as an input or output, using '' | + | "Each of the 14 digital pins on the Uno can be used as an input or output, using '' |
* **Serial: 0 (RX) and 1 (TX).** Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip. | * **Serial: 0 (RX) and 1 (TX).** Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip. | ||
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* **LED: 13.** There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off. | * **LED: 13.** There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off. | ||
- | The Uno has 6 analog inputs, labeled '' | + | "The Uno has 6 analog inputs, labeled '' |
* **TWI: A4 or SDA pin and A5 or SCL pin.** Support TWI communication using the Wire library. | * **TWI: A4 or SDA pin and A5 or SCL pin.** Support TWI communication using the Wire library. | ||
- | There are a couple of other pins on the board: | + | "There are a couple of other pins on the board: |
* **AREF.** Reference voltage for the analog inputs. Used with analogReference(). | * **AREF.** Reference voltage for the analog inputs. Used with analogReference(). | ||
- | * **Reset.** Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board. | + | * **Reset.** Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board." ((http:// |
- | ===== I/O config ===== | + | ==== "Most preferred" |
- | * "The analog input pins can be used as digital pins, referred to as A0, A1, etc." | + | Special functions are consumed by: |
- | ==== Binary output | + | * **I2C (TWI):** A4 and A5. |
+ | * **SPI:** 10, 11, 12, 13. | ||
+ | * **Interrupts: | ||
+ | * **Serial:** 0, 1 | ||
+ | |||
+ | This leaves: | ||
+ | |||
+ | * **Digital out/in:** 4, 7, 8 | ||
+ | * **PWM out:** 9, 10, and 11; pins 5 and 6 have higher-than-expected duty cycles. | ||
+ | * **Analog or digital out/in:** A0, A1, A2, A3 | ||
+ | |||
+ | Note that pin 13 also has a pullup resistor on it for the internal LED, meaning it's a poor choice for use as an input even if you're not using SPI. | ||
+ | |||
+ | ---- | ||
+ | |||
+ | |||
+ | ===== I/O ===== | ||
+ | |||
+ | ==== Output ==== | ||
+ | |||
+ | === Digital output | ||
* Output is limited to 40mA. More current draw can destroy the chip. | * Output is limited to 40mA. More current draw can destroy the chip. | ||
- | * There are no output resistors | + | * There are no output resistors. |
+ | * Some sources suggest that pin 13 on the Uno has a resistor. Examining the schematic suggests that the resistor is only connected to the internal LED. Pin 13 is naked. | ||
<code c> | <code c> | ||
- | const int LED = 13; | + | const int LED_PIN |
setup() { | setup() { | ||
- | pinMode(LED, OUTPUT); | + | pinMode(LED_PIN, OUTPUT); |
} | } | ||
loop() { | loop() { | ||
- | digitalWrite(LED, HIGH); | + | digitalWrite(LED_PIN, HIGH); |
- | digitalWrite(LED, LOW); | + | digitalWrite(LED_PIN, LOW); |
} | } | ||
</ | </ | ||
- | ==== PWM output | + | * "The analog input pins can be used as digital pins, referred to as A0, A1, etc." ((http:// |
+ | * "The analog pins can be used identically to the digital pins, using the aliases A0 (for analog input 0), A1, etc. For example, the code would look like this to set analog pin 0 to an output, and to set it HIGH: " ((http:// | ||
<code c> | <code c> | ||
- | const int LED = 11; /* 3,5,6,9,10,11 on Uno. */ | + | pinMode(A0, OUTPUT); |
+ | digitalWrite(A0, HIGH); | ||
+ | </code> | ||
- | setup() { | + | === PWM output === |
- | | + | * PWM around 490 or 980 Hz. |
- | } | + | * "You do not need to call pinMode() to set the pin as an output before calling analogWrite()." |
+ | | ||
+ | |||
+ | <code c> | ||
+ | const int LED_PIN = 11; /* 3, | ||
loop() { | loop() { | ||
- | analogWrite(LED, /*0 to 255*/); | + | analogWrite(LED_PIN, 127); /* 0 to 255. */ |
} | } | ||
</ | </ | ||
- | ==== Binary input ==== | + | ==== Input ==== |
- | * " | + | |
+ | === Digital input === | ||
+ | * " | ||
* Internal pullup resistors are disabled by default. | * Internal pullup resistors are disabled by default. | ||
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btnState = digitalRead(BUTTON); | btnState = digitalRead(BUTTON); | ||
} | } | ||
+ | </ | ||
+ | |||
+ | * "The analog input pins can be used as digital pins, referred to as A0, A1, etc." ((http:// | ||
+ | * "The analog pins can be used identically to the digital pins, using the aliases A0 (for analog input 0), A1, etc." ((http:// | ||
+ | |||
+ | <code c> | ||
+ | pinMode(A0, INPUT); | ||
+ | btnState = digitalRead(A0); | ||
</ | </ | ||
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"The value of this pullup depends on the microcontroller used. On most AVR-based boards, the value is guaranteed to be between 20kΩ and 50kΩ. On the Arduino Due, it is between 50kΩ and 150kΩ. | "The value of this pullup depends on the microcontroller used. On most AVR-based boards, the value is guaranteed to be between 20kΩ and 50kΩ. On the Arduino Due, it is between 50kΩ and 150kΩ. | ||
- | " | + | " |
<code c> | <code c> | ||
Line 80: | Line 119: | ||
</ | </ | ||
- | ==== A/D input ==== | + | === A/D input === |
+ | * 10-bit unsigned A/D conversion with about 10kHz sample rate. | ||
+ | * Default reference to 5VDC. Can be overridden via '' | ||
+ | * No setup is needed. | ||
<code c> | <code c> | ||
+ | int ANALOG_PIN = 3; // Maps to A3 we think. | ||
+ | int val = 0; | ||
+ | |||
+ | void loop() { | ||
+ | val = analogRead(ANALOG_PIN); | ||
+ | } | ||
</ | </ | ||
+ | ---- | ||
+ | |||
+ | ===== Serial communication ===== | ||
+ | |||
+ | * Serial I/O consumes pins 0 (for RX) and 1 (for TX) if used. | ||
+ | * [[http:// | ||
+ | |||
+ | ==== Serial output ==== | ||
+ | |||
+ | Simple reporting: | ||
+ | <code c> | ||
+ | void setup() { | ||
+ | Serial.begin(9600); | ||
+ | } | ||
+ | |||
+ | void loop() { | ||
+ | Serial.write(65); | ||
+ | Serial.print(42); | ||
+ | Serial.println(" | ||
+ | Serial.print(78, | ||
+ | Serial.println(1.23456, | ||
+ | Serial.end(); | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | ==== Serial output ==== | ||
+ | Later. | ||
+ | |||
+ | |||
+ | ---- | ||
arduino/arduino_crash_course/misc.1423975347.txt.gz · Last modified: 2015/02/15 04:42 by mithat