# Basic Wiring
:::success
- Prior knowledge:
- [Breadboard Introduction](https://www.youtube.com/watch?v=_j1oCHseWAc)
:::
## Pickit Appearance
5. **Indicator LEDs** of Pickit4 will show on the green line on the pickit4 in the figure.
>
6. **Push Button** of Pickit4 is the black circle on the pickit4 in the figure.
## [TTL](https://zh.wikipedia.org/wiki/%E9%9B%BB%E6%99%B6%E9%AB%94%EF%BC%8D%E9%9B%BB%E6%99%B6%E9%AB%94%E9%82%8F%E8%BC%AF)
> Red: +5V
> Black: GND
> Green: TXD(transmit data)(used in UART)
> White: RXD(receive data)(used in UART)
## Wiring
### PIC18F4520 Pins
### Pickit-PIC18F4520 Connection
- Pickit Pin 1 -- PIC18F4520 Pin 1(VPP)
- Pickit Pin 2 -- PIC18F4520 Pin 11(VDD)
- Pickit Pin 3 -- PIC18F4520 Pin 12(VSS)
- Pickit Pin 4 -- PIC18F4520 Pin 40(PGD)
- Pickit Pin 5 -- PIC18F4520 Pin 39(PGC)
###
## Example for Testing -- Control one LED
### Wiring
- Put the LED on the Pin19(RD0). **Remember to add a resistor to reduce the current.**
### Project Setting
- Select Tool: Pickit3 or Pickit4
- Select Compiler: mpasm
- New an assembly file and paste the following code

#include "p18f4520.inc"

  CONFIG  OSC = INTIO67         ; Oscillator Selection bits (Internal oscillator block, port function on RA6 and RA7)
  CONFIG  WDT = OFF             ; Watchdog Timer Enable bit (WDT disabled (control is placed on the SWDTEN bit))
  CONFIG  PBADEN = OFF           ; PORTB A/D Enable bit (PORTB<4:0> pins are configured as analog input channels on Reset)
  CONFIG  LVP = OFF             ; Single-Supply ICSP Enable bit (Single-Supply ICSP disabled)
  org 0x00
    
    init:
    CLRF    TRISD	; set PORTD as output
    CLRF    LATD	; 0000 0000 , RD0~RD7 = 0
    
    s1:
    INCF    LATD	; 0000 0001 , RD0 = 1, turn on RD0
    NOP
    
    end

### Run Project
1. Set up the breakpoint at line `CLRF LATD` and Debug Main Project. **The LED is off now.**
2. Press F7(step over). **RD0 = 1. The LED is on.**
3. Modify the LATD to 0x00 in SFRs(You will see the LED is off now.)
## FAQ
## Reference
- [Why do we use a USB to TTL converter?](https://www.quora.com/What-is-a-TTL-signal-in-communication-and-when-using-a-USB-port-why-do-we-use-a-USB-to-TTL-converter)
- [Pickit 3 User Manual](https://www.sparkfun.com/datasheets/Programmers/PICkit_3_User_Guide_51795A.pdf)
- [Pickit 4 User Manual](http://ww1.microchip.com/downloads/en/DeviceDoc/MPLAB_PICkit4_Debugger_UG_DS50002751A.pdf)