ODROID – A Raspberry Pi Alternative

The ODROID is a series of single-board computers manufactured by Hardkernel in South Korea. The ODROID-C1+ ($35) and the ODROID-C2 ($46) have a form factor similar to the Raspberry Pi 3. The higher end ODROID-XU($59) which is around 5 times faster than the Pi 3 has a signifigently different board layout.

For my testing I looked at the ODROID-C2 ($46), it is a little more expensive than a Pi 3 but the literature states that it’s 2-3 times faster.

My goal was to see if I could use the ODROID-C2 for some typical Raspberry Pi applications. In this blog I will be looking at doing C, Python and NodeRed programming from a Pi user perspective.

OD_PI

I’ve been happy with the functionality and openness of the Raspberry Pi platform, however I find its desktop performance to be sluggish. For only a few dollars more than a Pi 3 the ODROID-C2 CPU, RAM and GPU specs are impressive.

ODROID-C2 / Raspberry Pi 3 Hardware Comparison
Odroid C2 Raspberry Pi 3
CPU Amlogic S905 SoC
4 x ARM Cortex-A53 1.5GHz
64bit ARMv8 Architecture @28nm
Broadcom BCM2837
4 x ARM Cortex-A53 1.2Ghz
64bit ARMv7 Architecture @40nm
RAM 2GB 32bit DDR3 912MHz 1GB 32bit LPDDR2 450MHz
GPU 3 x ARM Mali-450 MP 700MHz 1 x VideoCore IV 250MHz
USB 4 Ports 4 Ports
Ethernet / LAN 10 / 100 / 1000 Mbit/s 10 / 100 Mbit/s
Built in WiFi No Yes
Built in Bluetooth No Yes
IR Receiver Built in Needs add-on
I/O Expansion 40 + 7 pin port
GPIO / UART / I2C / I2S / ADC
40 pin port
GPIO / UART / SPI / I2S
Camera Input USB 720p MIPI CSI 1080p
List Price (US) $46 $35

First Impressions

The ODROID-C2 is almost the same footprint as the Raspberry Pi 3 but not exactly. I found that because the microSD mounting is different some, but not all, of my Pi cases could be used .

lego_case

When you are designing your projects it is important to note that the ODROID-C2 does not have a built in Wifi or Bluetooth adapters, so you’ll need wired connections or USB adapters. Like some of the Orange Pi modules the ODROID-C2 has a built-in IR connection.

ODROID-C2 can be loaded with Ubuntu, Arch Linux and Android images. For my testing I used the Armbian 5.40 Ubuntu desktop and the performance was signifigently faster than my Raspberry Pi 3 Raspian desktop. I could definitely see ODROID-C2 being used as a low cost Web browser station.

The ODROID-C2 images are quite lean, so you will need to go the ODROID Wiki, https://wiki.odroid.com, for instructions on loading additional software components.

The ODROID-C2 has a 40 pin General Purpose Input/Output (GPIO) arrangement like the Pi 3, so it is possible to use Pi prototyping hats on the ODROID-C2 .

pi_hats

There are some noticeable differences in the pin definitions between the two modules, so for this reason I didn’t risk using any of my intelligent Pi hats on the ODROID-C2. The gpio command line tool can be used to view the pin definitions:

Od_readall

The Raspberry Pi GPIO names are in the range of 2 to 27, whereas the ODROID-C2 GPIO ranges are in the 200’s, because of this don’t expect to be able to run all your Raspberry Pi code “as is” on the ODROID-C2.

Unlike the Arduino the Raspberry Pi platform has no built in support for analog inputs. I got pretty excited when I noticed that the ODROID-C2 had two built in Analog-to-Digital Converter (ADC) pins (AIN.1 on pin 37 and AIN.0 on pin 40). However after some investigation I found that these pins had virtually no example code and they only support 1.8 volts. Most of my analog input sensors require 3.3V or 5V so I’m not sure how often these ADC pins will be used.

Python Applications

The ODROID-C2 Wiki references the RPi.GPIO and wiringpi Python libraries. I tested both of these libraries and I found that standard reads and writes worked, but neither of these libraries supported the callback functions like the Raspberry Pi versions.

For existing Pi projects where you are using callback functions for rising and/or falling digital signals (like intrusion alarms) you will need to do some re-coding with a polling method. It’s also important to note that the ODROID RPi.GPIO library is a little confusing because it uses the Pi pin names and not the ODROID pin names, so for example ODROID-C2 physical pin 7 is referenced as GPIO.04 (as on a PI) and not GPIO.249 (the ODROID-C2 name). Below is simple Python example that polls for a button press and then toggles an LED output when a button press is caught.

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)

button = 4 # physical pin 7, PI GPIO.04, ODROID-C2 GPIO.249
led = 17 # physical pin 11, PI GPIO.17, ODROID-C2 GPIO.247
GPIO.setup(led, GPIO.OUT, initial=GPIO.LOW)
GPIO.setup(button, GPIO.IN, pull_up_down = GPIO.PUD_UP)

print ('Wait for button...')
while True:
    if GPIO.input(button) == 1:
        GPIO.output(led,0)
    else:
    GPIO.output(led,1)
    print "button pressed"

There are some excellent Python libraries that are designed to work with the Raspberry Pi. However it will require some trial and error to determine which libraries will and won’t work with the ODROID-C2.

I tried testing the DHT11 temperature and humidity sensor with the ODROID-C2, and unfortunately the library had a “Segmentation Error” when I tried running an example.

Node-Red

NodeRed can be installed on ODROID-C2 by using the manual install instructions for Raspbian at nodered.org. This install procedure will add a start item to the desktop Application menu, but due to hardware differences the Raspberry Pi GPIO input/output components will not load.

To read and write to Raspberry Pi GPIO a simple workaround is to use exec nodes to call the gpio utility.

Odroid_NodeRed

The command line syntax for writing a gpio output is: gpio write pin state, and for reading it is: gpio read pin. One of the limitations of this workaround is that you will need to add a polling mechanism, luckily there are some good scheduling nodes such as Big Timer that can be used.

C Applications

Programming in C is fairly well documented and an ODROID “C Tinkering Kit” is sold separately. The wiringPi library is used in C applications.

Below is a C version of the Python example above. It is important to note that these 2 examples talk to the same physical pins but the C wiringPi library uses the ODROID-C2 wPi numbers and the Python RPi.GPIO library uses the Pi BCM numbers.

// led.c - Read/Write "C" example for an Odroid-C2
//
#include  <wiringPi.h>

int main(void)
{
    wiringPiSetup();
    int led = 0;
    int button = 7;
    pinMode(led, OUTPUT);
    pinMode(button, INPUT);
 
    for (;;)
    {
        if (digitalRead(button) == 1) {
           digitalWrite(led, LOW); 
        }
	else
	{
           digitalWrite(led, HIGH); 
        }
    }
    return 0;
}

To compile and run this program:

$ gcc -o led led.c -lwiringPi -lpthread
$ sudo ./led

Summary

I liked that I could reuse some of my Pi cases and prototyping hats with the ODROID-C2.

As a PI user I found that coding in C, Python and NodeRed on the ODROID-C2 was fairly easy, but there were many limitation compared to the Pi platform. The ODROID Wiki had the key product documentation, but it was no where near the incredibly rich documentation that exists with Raspberry Pi modules.

There are a some excellent Python libraries and PI hardware add-ons that support a variety of sensors and I/O applications, these may or not work with the ODROID hardware.

During the development cycle of a project it is nice to have a faster interface, but typically my final projects do not need any high end processing and they can often run on low end Raspberry Pi 1 modules. So for now I would stick to a Raspberry Pi for GPIO/hardware type projects.

I enjoying playing with the ODROID-C2 and for projects requiring higher performance such as video servers, graphic or Web applications then the ODROID-C2 module is definitely worth considering.