Difference between Arduino and 8051(89c51,89c52) Microcontrollers

• 8051(MCS51) Developed by Intel in 1980.
• Followed Harvard Architecture-CISC (Complex Instruction Set Computer). 
• ​8051 is an 8-bit microcontroller. 16 and 32 bit are also available in market. But we will only focus on 8-bit controllers.

• Developed at at the Interaction Design Institute Ivrea (IDII) in Ivrea, Italy in 2003 by some graduating students.
• Followed Modified Harvard Architecture-RISC(Reduced instruction set computing)
• Arduino houses 8-bit AVR microcontrollers. 32 bit development boards are also released but we will focus on general 8-bits.
• The initial version is named as Arduino Uno and it houses an AVR Atmega328 microcontroller.
• Other development board also comes out with time that houses many other AVR series microcntrollers such as ATmega8, ATmega168, ATmega1280, ATmega2560 

• 8051 operating voltage is between +5 volts to max 6.6 volts.
  
• 8051 operating minimum current is 25 mA.
  
• Its GPIO pins can source out 15mA at Max.

• Arduino boards can work on +5 volts to max 20 volts. On board voltage regulators converters input voltages to +5 volts for microcontroller operation. 
• Arduino boards can be powered through USB port of computer/laptop as well as with external adopter.
• Arduino boards are present in logic 5 volts and 3.3 volts. This makes arduino more versatile than 8051. We can interface 5 volt logic devices with 5 volt logic boards and 3.3 volt sensors with 3.3 volts boards. We don’t need to have a level converter. 
• Arduino minimum operating current is 25mA. Approximately same as 8051.
• Its GPIO pins can source out 40mA of current. A big advantage on 8051 gpio’s.

• Flash Memory = 8 kB
• RAM(Random Access Memory) = 256 Bytes
• EEPROM= No eeprom

More recent 8051 microcontrollers contains eeprom in them, but many popular 8051 series microcontrollers do not have eeprom in them.
​

• Arduino uno Flash Memory = 32 kB
• Arduino uno RAM(Random Access Memory) = 2 kB
• Arduino uno EEPROM= 1 kB

The upper features are of arduino uno board others boards offer more flash, ram and eeprom.

• Clock speed = 12 Mhz 
  
• ​One machine cycle = 12 clock cycles
  
• ​Single instruction executed in 2 machine cycles
  
• More recent microcontrollers have clock speed higher than 100 Mhz but their speed is always less than their equivalent arduino boards.

• Clock Speed = 16 Mhz could be increase to 20 Mhz
• ​One machine cycle = 1 clock cycle
• Single instruction executed in single machine cycle 

Thus arduino has more instruction executing speed.

• Generally keil Uvision IDE is used to write and compile code for 8051 microcontroller.
• One has to know about the registers and pins definitions by compiler to write code for 8051 microcontroller.
• To upload code in 8051 flash we need an external programmer. ​​

• Arduino Ide is used to write compile and upload code to the board.
• A lay man can easily write code for arduino in arduino ide. Its very simple and easy to understand.
• In arduino flash we can upload code by just connecting the board usb port with out computer/laptop and pressing the upload button in arduino ide. We do not need an external programmer. Arduino board has programmer built on it. 

• 40 pin package offers 32 GPIO pins.
  
• Supports hardware and software interrupts, internal as well as external.
  
• No internal pull up resistors.
  
• Offer 8/16 bit timers event/counters.
  
• No built in ADC(analog to digital converter).
  
• One RS232 Uart.
  
• No I2C interface.
  
• No SPI interface.

• ​Arduino uno GPIO pins = 14 + 6(ADC) analog to digital pins- can be used as digital. So total GPIO pins = 20
  
• Supports hardware and software interrupts, internal as well as external.
  
• Internal pull up resistors available (10k)
  
• ​Offer 8/16 bit timers event/counters.
  
• Offers 6 ADC(analog to digital channels)
  
• One-Two RS232 Uart channels.
  
• One I2C interface.
  
• One SPI interface.

• Some 8051 development kits are available in market, but the support is poor.
• Lesser development community.  
• Very few sensors kits available in market.

• Many development kits are available in market, with strong support.
• Huge development community and forums.
• Many sensors. actuators, motors kits are available in market which reduces circuit making and development time such as rtc(real time clock), temperature, motor drivers, water level sensors, gas sensors etc .

Shields are available in market which can be mounted on the arduino board and can be used instantly. Some arduino stack-able shields.

• Arduino lcd shield.
• Arduino WIFI shield.
• Arduino GSM and GPS shield.
• Arduino Ethernet shield