vbox-firmware/azero_pins.md

SAMD21 Pinout Table

Pin Number	Board Pin	Pin	Label/Name	Comments
	Digital Low
0	0 -> RX	PA11		EIC/EXTINT[11] ADC/AIN[19] PTC/X[3] *SERCOM0/PAD[3] SERCOM2/PAD[3] TCC0/WO[3] TCC1/WO[1]
1	1 <- TX	PA10		EIC/EXTINT[10] ADC/AIN[18] PTC/X[2] *SERCOM0/PAD[2] TCC0/WO[2] TCC1/WO[0]
2	2	PA14		EIC/EXTINT[14] SERCOM2/PAD[2] SERCOM4/PAD[2] TC3/WO[0] TCC0/WO[4]
3	~3	PA09		EIC/EXTINT[9] ADC/AIN[17] PTC/X[1] SERCOM0/PAD[1] SERCOM2/PAD[1] *TCC0/WO[1] TCC1/WO[3]
4	~4	PA08		EIC/NMI ADC/AIN[16] PTC/X[0] SERCOM0/PAD[0] SERCOM2/PAD[0] *TCC0/WO[0] TCC1/WO[2]
5	~5	PA15		EIC/EXTINT[15] SERCOM2/PAD[3] SERCOM4/PAD[3] *TC3/WO[1] TCC0/WO[5]
6	~6	PA20		EIC/EXTINT[4] PTC/X[8] SERCOM5/PAD[2] SERCOM3/PAD[2] *TCC0/WO[6]
7	7	PA21		EIC/EXTINT[5] PTC/X[9] SERCOM5/PAD[3] SERCOM3/PAD[3] TCC0/WO[7]
	Digital High
8	~8	PA06		EIC/EXTINT[6] ADC/AIN[6] AC/AIN[2] PTC/Y[4] SERCOM0/PAD[2] *TCC1/WO[0]
9	~9	PA07		EIC/EXTINT[7] ADC/AIN[7] AC/AIN[3] PTC/Y[5] SERCOM0/PAD[3] *TCC1/WO[1]
10	~10	PA18		EIC/EXTINT[2] PTC/X[6] +SERCOM1/PAD[2] SERCOM3/PAD[2] *TC3/WO[0] TCC0/WO[2]
11	~11	PA16		EIC/EXTINT[0] PTC/X[4] +SERCOM1/PAD[0] SERCOM3/PAD[0] *TCC2/WO[0] TCC0/WO[6]
12	~12	PA19		EIC/EXTINT[3] PTC/X[7] +SERCOM1/PAD[3] SERCOM3/PAD[3] TC3/WO[1] *TCC0/WO[3]
13	~13	PA17		EIC/EXTINT[1] PTC/X[5] +SERCOM1/PAD[1] SERCOM3/PAD[1] *TCC2/WO[1] TCC0/WO[7]
	Analog Connector
14	A0	PA02		EIC/EXTINT[2] *ADC/AIN[0] DAC/VOUT PTC/Y[0]
15	A1	PB08		EIC/EXTINT[8] *ADC/AIN[2] PTC/Y[14] SERCOM4/PAD[0] TC4/WO[0]
16	A2	PB09		EIC/EXTINT[9] *ADC/AIN[3] PTC/Y[15] SERCOM4/PAD[1] TC4/WO[1]
17	A3	PA04		EIC/EXTINT[4] *ADC/AIN[4] AC/AIN[0] PTC/Y[2] SERCOM0/PAD[0] TCC0/WO[0]
18	A4	PA05		EIC/EXTINT[5] *ADC/AIN[5] AC/AIN[1] PTC/Y[5] SERCOM0/PAD[1] TCC0/WO[1]
19	A5	PB02		EIC/EXTINT[2] *ADC/AIN[10] PTC/Y[8] SERCOM5/PAD[0]
	Wire
20	SDA	PA22		EIC/EXTINT[6] PTC/X[10] *SERCOM3/PAD[0] SERCOM5/PAD[0] TC4/WO[0] TCC0/WO[4]
21	SCL	PA23		EIC/EXTINT[7] PTC/X[11] *SERCOM3/PAD[1] SERCOM5/PAD[1] TC4/WO[1] TCC0/WO[5]
	SPI (Legacy ICSP)
22	1	PA12		EIC/EXTINT[12] SERCOM2/PAD[0] *SERCOM4/PAD[0] TCC2/WO[0] TCC0/WO[6]
	2
23	4	PB10		EIC/EXTINT[10] *SERCOM4/PAD[2] TC5/WO[0] TCC0/WO[4]
24	3	PB11		EIC/EXTINT[11] *SERCOM4/PAD[3] TC5/WO[1] TCC0/WO[5]
	5
	6
	USB
27		PA28		EIC/EXTINT[8]
28		PA24		*USB/DM
29		PA25		*USB/DP
	LEDs
25		PB03
26		PA27
	EDBG
30		PB22		*SERCOM5/PAD[2]
31		PB23		*SERCOM5/PAD[3]
32		PA22		Pin 20 (SDA)
33		PA23		Pin 21 (SCL)
34		PA19		EIC/EXTINT[3] *SERCOM1/PAD[3] SERCOM3/PAD[3] TC3/WO[1] TCC0/WO[3]
35		PA16		EIC/EXTINT[0] *SERCOM1/PAD[0] SERCOM3/PAD[0] TCC2/WO[0] TCC0/WO[6]
36		PA18		EIC/EXTINT[2] *SERCOM1/PAD[2] SERCOM3/PAD[2] TC3/WO[0] TCC0/WO[2]
45		PA31		SWDIO, alternate use EXTINT[11] TCC1/WO[1] SERCOM1/PAD[3]
37		PA17		EIC/EXTINT[1] *SERCOM1/PAD[1] SERCOM3/PAD[1] TCC2/WO[1] TCC0/WO[7]
38	ATN	PA13		EIC/EXTINT[13] SERCOM2/PAD[1] SERCOM4/PAD[1] *TCC2/WO[1] TCC0/WO[7]
39		PA21		Pin 7
40		PA06		Pin 8
41		PA07		Pin 9
	GND
42	AREF	PA03		EIC/EXTINT[3] *[ADC
43		PA02		Alternate use of A0 (DAC output)
44		PA30		SWCLK, alternate use EXTINT[10] TCC1/WO[0] SERCOM1/PAD[2]

what does EIC/EXTINT[11] means ?

In the context of the SAMD21 microcontroller, EIC/EXTINT[11] is a reference to a specific external interrupt configuration on pin PA11 (or other associated pins depending on the device's pin mapping).

Breakdown of Terms

• EIC:

  • Stands for External Interrupt Controller.
  • The EIC manages external interrupts from the microcontroller's I/O pins.

• EXTINT[11]:

  • Refers to External Interrupt Line 11.
  • The number inside the brackets (11) identifies which external interrupt line is associated with the specific pin.
  • In this example, PA11 would likely be mapped to EXTINT[11].

How It Works

When PA11 is configured with EIC/EXTINT[11], it means the pin can trigger an interrupt when a specific signal change (rising edge, falling edge, or level change) occurs.

Typical Usage

1. Wake-up from Sleep: External interrupts can wake up the SAMD21 from a low-power state.
2. Button Press Detection: Connecting a button to PA11 and enabling the EXTINT[11] interrupt allows the microcontroller to handle button events asynchronously.
3. Event-Driven Systems: Useful for monitoring external signals without constantly polling the pin.

Example in Code

Using Arduino with the SAMD21:

attachInterrupt(digitalPinToInterrupt(11), myInterruptHandler, RISING);

In this example:

• The digitalPinToInterrupt(11) would map to PA11 with EXTINT[11] behind the scenes.
• RISING triggers the interrupt on a rising edge.

what does PTC/X[3] means ?

PTC/X[3] on the SAMD21 refers to a specific pin's capability as part of the Peripheral Touch Controller (PTC).

Breakdown

• PTC:

  • Stands for Peripheral Touch Controller.
  • This is a hardware module on the SAMD21 designed for capacitive touch sensing applications, such as touch buttons, sliders, and wheels.

• X[3]:

  • The X-line 3 refers to one of the electrode channels used for touch detection.
  • The PTC uses a matrix of X-lines (transmitter) and Y-lines (receiver) to measure capacitance changes on a touch-sensitive electrode.

How It Works

• Each X-line is connected to a specific GPIO pin on the microcontroller.
• When configured for touch sensing, the pin generates a signal to detect changes in capacitance caused by a finger touching the corresponding electrode.

Example Use Case

If you're designing a capacitive touch button using X[3], you would:

1. Connect the electrode to the pin corresponding to PTC/X[3].
2. Enable and configure the PTC in your firmware to monitor capacitance changes on this pin.

Why It Matters

• Using PTC/X[3] allows you to implement touch-sensitive controls without needing additional external ICs.
• The SAMD21 provides efficient touch sensing hardware, reducing the need for software-based polling.