In this post update, We will compare different micro-controller candidates based on multiple criteria and examine each candidate as a possible processor option of each micro node.

The main two criteria of selecting the node micro-controller are the cost and availability of the micro-controller in the third world countries. Other criteria are power consumption, processing power, buffer depth for the Bluetooth and Wi-Fi links, memory speed and memory cost.

Small Memory size can be an issue if each node stores and forwards multiple message which can lead to a high message traffic even if only short text messages are sent. The micro-controller should be selected carefully to make sure each message is delivered. The node system can be slow as SMS without guarantee of timely delivery of messages but the system should not lose messages due to limitation of network data throughput.

Here are microcontroller candidates:

• Raspberry Pi Zero W
• Raspberry Pi 2
• Raspberry Pi 3
• Arduino Yún
• Arduino MKR1000
• Particle Photon
• Adafruit Feather nRF52 Bluefruit LE
• Adafruit Feather HUZZAH with ESP8266 WiFi
  
• Omega2
• ODROID-C0
• WiPy 2.0
• Intel® Edison

Raspberry Pi Zero W

• SoC: Broadcom BCM2835
• CPU: 1 GHz ARM11 Broadcom CPU
• Memory: 512 MB
• Storage: microSD card slot 4GB and more
• OS: Linux
• Wireless Connection: 802.11n wireless LAN , Bluetooth Low Energy, Bluetooth 4.1
• Wireless Chip: Cypress BCM43438 CYW43438
• USB: 1 micro USB
• Power consumption:
  • 5.25V @ 2A
  • IDLE: 0.12 A
  • LOAD: 0.23 A
• Price: $10

Raspberry Pi 3 B

• SoC: Broadcom BCM2837 (roughly 50% faster than the Pi 2)
• CPU: 1.2 GHz quad-core ARM Cortex-A53 CPU
• Memory: 1 GB
• Storage: microSD card slot 4GB and more
• OS: Linux
• Wireless Connection: on-board 802.11n wireless LAN , Bluetooth Low Energy, Bluetooth 4.0
• Wireless Chip: Cypress BCM43438 CYW43438
• USB: 4 x USB 2 ports
• Power consumption:
  • 5.25V @ 2A
  • IDLE: 0.23 A - 0.31 A
  • LOAD: 1 Thread : 0.35 A - 4 Threads: 0.72 A
• Price: $35

Raspberry Pi 2 B

• SoC: Broadcom BCM2836
• CPU: 900 MHz quad-core ARM Cortex A7
• Memory: 1 GB
• Storage: microSD card slot 4GB and more
• OS: Linux
• Wireless Connection: No on-board 802.11n wireless LAN , No on-boardBluetooth
• USB: 4 x USB 2 ports
• Power consumption:
  • 5.25V @ 2A
  • IDLE: 0.23 A
  • LOAD: 1 Thread : 0.28 A - 4 Threads:0.42 A
• Price: $35

Arduino Yún

• CPU: ATmega32U4
• Memory: 64 MB DDR2
• Storage: 16 MB and MicroSD Card slot
• Wireless Connection: on-board 802.11b/g/n 2.4 GHz
• USB: 1 x USB 2 ports
• Wireless Chip: Atheros AR9331
• Power consumption:
  • 5 V @ 2A
  • LOAD: 1 Thread : 0.28 A
• Price: $ 68.20

https://store.arduino.cc/usa/arduino-yun

Arduino MKR1000

• CPU: SAMD21 Cortex-M0+ 32bit low power ARM MCU
• Flash Memory: 256 KB
• SRAM: 32 KB
• EEPROM: NO
• Wireless Connection: on-board low power 802.11 b/g/n WiFi network
• USB: 1 Micro USB
• Wireless Chip: WINC1500
• Power consumption:
  • 5 V @ 2A
  • LOAD: 1 Thread : 0.12 A
• Price: $ 34.99

https://store.arduino.cc/usa/arduino-mkr1000

Particle Photon

• CPU: STM32 ARM Cortex M3
• Flash Memory: 1MB
• SRAM: 128K
• Wireless Connection: on-board low power 2.4GHz IEEE 802.11b/g/n
• USB: 1 Micro USB
• Wireless Chip: Cypress BCM43362 Wi-Fi chip
• Power consumption:
• 5 V @ 1A
• Price: $19.00

https://www.particle.io/products/hardware/photon-wifi-dev-kit

Adafruit Feather nRF52 Bluefruit LE

• CPU: ARM Cortex M4F
• Flash Memory: 512KB
• SRAM: 64KB
• Wireless Connection: Bluetooth LE
• USB: 1 Micro USB ( Only for programming )
• Wireless Chip: nRF52832 Bluetooth chip-set from Nordic
• Power consumption:
  • 5 V @ 2A
• Price: $ 24.95

https://www.adafruit.com/product/3406

Adafruit Feather HUZZAH with ESP8266 WiFi

• CPU: ARM Cortex M4F
• Flash Memory: 4MB
• SRAM: 128KB
• Wireless Connection: on-board low power 2.4GHz IEEE 802.11b/g/n
• USB: 1 Micro USB ( Only for programming )
• Wireless Chip: ESP8266 Wi-Fi Chipset
• Power consumption:
  • 5 V @ 2A
  • LOAD: 1 Thread : 0.25 A to 0.35 A
• Price: $16.95

https://www.adafruit.com/product/2821

Omega2

• CPU: MIPS32® 24Kc
• Flash Memory: 64 MB
• SRAM: 16 MB
• Wireless Connection: on-board low power 2.4GHz IEEE 802.11b/g/n
• Bluetooth connection requires Bluetooth extension board which adds to the cost
• Omega’s WiFi signal is able to travel up to 100m. An external antenna can be used to extend the range of WiFi connectivity or provide a very directional signal
• USB: 1 Micro USB
• Power consumption:
  • 5 V @ 1A
• Price: $7.5

https://onion.io/omega2/

ODROID-C0

• CPU: Amlogic ARM® Cortex®-A5
• Flash Memory: eMMC4.5 HS200 Flash Storage slot / UHS-1 SDR50 MicroSD Card slot
• SRAM: 1Gbyte DDR3 SDRAM
• Wireless Connection: No on-board low power 2.4GHz IEEE 802.11b/g/n and No Bluetooth chipset
• USB: 1 x USB 2 ports
• Power consumption:
  • 5 V @ 2A
• Price: $28

http://www.hardkernel.com/main/products/prdt_info.php?g_code=G145326484280

WiPy 2.0

• CPU: Espressif ESP32 dual processor 2.4 GHz Wi-Fi and Bluetooth combo chip
• Flash Memory: 4MB and MicroSD Card slot
• RAM: 512KB
• Wireless Connection: on-board 802.11b/g/n 16 mbps with 1km range and on-board Bluetooth LE
• USB: 1 x USB 2 ports
• Power consumption:
• 3.3V – 5.5V
• LOAD: 260mA
• Price: $22

https://www.seeedstudio.com/WiPy-2.0-p-2786.html

Intel Edison

• CPU: Atom 2-Core 2.4 GHz Wi-Fi and Bluetooth combo chip
• Flash Memory: 4 GB EMMC
• RAM: 1 GB
• Wireless Connection: on-board 802.11b/g/n and on-board Bluetooth LE
• USB: 2 x Micro USB 2 ports when Breakout Kit is added
• Power consumption:
  • 3.15-4.5 V
• It requires Breakout Kit to be programmed
• Price: $49.95 and $74.95 with Breakout Kit

https://software.intel.com/en-us/iot/hardware/edison

Summary

After comparing all the candidates,it can be concluded that raspberry pi zero W offers all the necessary features mentioned list of criteria. raspberry pi zero W has an affordable cost for third world countries and offers both Bluetooth and Wi-Fi Chip-set.The flash Memory can be extended by switching the micro SD card and external USB Antenna can be added as well.Omega2 offers smaller Memory size and requires external Bluetooth Chip-set which adds to the cost.WiPy 2.0 offers smaller Memory size comparing to raspberry pi zero W but it offers on board long range ( 1 KM ) on-board 802.11b/g/n Wi-Fi chip-set and on-board Bluetooth LE chip-set. WiPy 2.0 offers the option to add external antenna the extend Wi-Fi.

We will go over external antenna options in future posts/updates.