/*
Quick GPIO reference for pin and function 
Paste at the top of your program

GPIO   | Label | Notes              | Assingment 
-------|-------|--------------------|----------------
GPIO01 | TXD   | UART0 TX           |  
GPIO02 | D2    | Built-in LED       | ext Led 
GPIO03 | RXD   | UART0 RX           |  
GPIO04 | D4    | PWM, SPI           | DS18B20 
GPIO05 | D5    | PWM, SPI           |  
GPIO12 | D12   | PWM, SPI, I2C      |  
GPIO13 | D13   | PWM, SPI, I2C      |  
GPIO14 | D14   | PWM, SPI, I2C      |  
GPIO15 | D15   | PWM, SPI           |  
GPIO16 | RX2   | UART2 RX           |  
GPIO17 | TX2   | UART2 TX           |  
GPIO18 | D18   | PWM, SPI           |  
GPIO19 | D19   | PWM, SPI           |  
GPIO21 | D21   | PWM, I2C           |  
GPIO22 | D22   | PWM, SPI, I2C      |  
GPIO23 | D23   | PWM, SPI           |  
GPIO25 | D25   | DAC, can be output |  
GPIO26 | D26   | DAC, can be output |  
GPIO27 | D27   | ADC, can be input  |  
GPIO32 | D32   | ADC, can be input  |  
GPIO33 | D33   | ADC, can be input  |  
GPIO34 | D34   | Input-only (ADC)   |  
GPIO35 | D35   | Input-only (ADC)   |  
GPIO36 | VP    | Input-only (ADC)   |  
GPIO39 | VN    | Input-only (ADC)   |  
*/