Preparing Raspberry Pi 3

Install Raspbian Jessie on the Raspberry Pi 3

It is highly recommended to install Raspbian Jessie releases on 18th March 2016. http://downloads.raspberrypi.org/raspbian/images/raspbian-2016-03-18/2016-03-18-raspbian-jessie.zip

Expand file system

Expand file system by following this: https://www.raspberrypi.org/documentation/configuration/raspi-config.md

Update and Upgrade Packages

sudo apt-get update
sudo apt-get upgrade

Download sample code.

cd ~
git clone https://github.com/AtlasScientific/Raspberry-Pi-sample-code.git

FTDI MODE

FTDI mode works with Atlas Scientific's FTDI based USB to Serial devices such as the Electrically Isolated USB EZO™ Carrier Board and the Basic USB to Serial Converter

Installing dependencies for FTDI adaptors

• Install libftdi package.

    sudo apt-get install libftdi-dev
  

• Install pylibftdi python package.

    sudo pip install pylibftdi
  

• Create SYMLINK of the FTDI adaptors. NOTE: If you are using device with root permission, just skip this step.

  The following will allow ordinary users (e.g. ‘pi’ on the RPi) to access to the FTDI device without needing root permissions:

  Create udev rule file by typing sudo nano /etc/udev/rules.d/99-libftdi.rules and insert below:

    SUBSYSTEMS=="usb", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6015", GROUP="dialout", MODE="0660", SYMLINK+="FTDISerial_Converter_$attr{serial}"
  

  Press CTRL+X, Y and hit Enter to save & exit.

  Restart udev service to apply changes above.

    sudo service udev restart
  

• Modify FTDI python driver

  Since our FTDI devices use other USB PID(0x6015), we need to tweak the original FTDI Driver.

    sudo nano /usr/local/lib/python2.7/dist-packages/pylibftdi/driver.py
  

  Move down to the line 70 and add 0x6015 at the end of line.

  Original line:

    USB_PID_LIST = [0x6001, 0x6010, 0x6011, 0x6014]
  

  Added line:

    USB_PID_LIST = [0x6001, 0x6010, 0x6011, 0x6014, 0x6015]        
  

• Testing Installation.

  Connect your device, and run the following (as a regular user):

    python -m pylibftdi.examples.list_devices
  

  If all goes well, the program should report information about each connected device.

  If no information is printed, but it is when run with sudo, a possibility is permissions problems - see the section under Linux above regarding udev rules.

  You may get result like this:

    FTDI:FT230X Basic UART:DA00TN73
  

  FTDI adaptors has its own unique serial number.

  We need this to work with our sensors.

  In the result above, serial number is DA00TN73.

Using pylibftdi module for Atlas Sensors.

Run the sample code.

cd ~/Raspberry-Pi-sample-code
sudo python ftdi.py

When the program opens, it will give a list of available serial numbers. Type in the index number of the serial port you want the program to open to start communication.

For more details on the commands & responses, please refer the Datasheet of your Atlas Scientific sensors.

I2C MODE

I2C mode uses the GPIO I2C port on the Raspberry Pi to talk to one or more Atlas Scientific sensors.

Enable I2C bus on the Raspberry Pi

Enable I2C bus on the Raspberry Pi by following this:

https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c

You can confirm this with sudo i2cdetect -y 1 command.

Test Sensor

Run the sample code like below:

cd ~/Raspberry-Pi-sample-code
sudo python i2c.py

The default I2C address is 98(0x62).

To see the available I2C addresses, use List_addr command.

If you need to change the address, input ADDRESS,99 to change the address to 99(0x63)

If you need to get sensor data continuously, input POLL,3 to get data with time interval of 3 seconds.

For more details on the commands & responses, please refer the Datasheets of Atlas Sensors.

UART MODE

This mode allows use of the GPIO UART as well as non FTDI based serial port devices.

NOTE: This mode doesnt work with the Pi 3 when using the GPIO UART

Preventing Raspberry Pi from taking up the serial port

The Broadcom UART appears as /dev/ttyS0 under Linux.

There are several minor things in the way if you want to have dedicated control of the serial port on a Raspberry Pi.

• Firstly, the kernel will use the port as controlled by kernel command line contained in /boot/cmdline.txt.

  The file will look something like this:

    dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
  

  The console keyword outputs messages during boot, and the kgdboc keyword enables kernel debugging.

  You will need to remove all references to ttyAMA0.

  So, for the example above /boot/cmdline.txt, should contain:

    dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
  

  You must be root to edit this (e.g. use sudo nano /boot/cmdline.txt).

  Be careful doing this, as a faulty command line can prevent the system booting.

• Secondly, after booting, a login prompt appears on the serial port.

  This is controlled by the following lines in /etc/inittab:

    #Spawn a getty on Raspberry Pi serial line
    T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100
  

  You will need to edit this file to comment out the second line, i.e.

    #T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100
  

• Finally you will need to reboot the Raspberry Pi for the new settings to take effect.

  Once this is done, you can use /dev/ttyS0 like any normal Linux serial port, and you won't get any unwanted traffic confusing the attached devices.

To double-check, use

cat /proc/cmdline

to show the current kernel command line, and

ps aux | grep ttyS0

to search for getty processes using the serial port.

Ensure PySerial is installed for Python.

sudo pip install pyserial

Run the below Python script:

cd ~/Raspberry-Pi-sample-code
sudo python uart.py

To use other serial ports:

change the line

usbport = '/dev/ttyAMA0'

in uart.py to point to the serial port you wish to use and run the script.