Spark Connection Settings
The Spark service can connect to the controller using either Wifi, or USB.
Controllers can either be automatically discovered, or connected to by address.
Connection settings are specified by editing the Spark service arguments in the
Wifi vs USB
Wifi and USB have their own set of advantages and disadvantages while connecting. Once connected, both will behave the same.
- Spark controller must be in the same Wifi network as the service host (Raspberry Pi).
- Spark controller must be logged in to the wifi network (
- Spark controller must be connected to service host (Raspberry Pi) over USB.
- Spark controller must be plugged in before Spark service is started.
Discovery vs Address
The Spark service is able to automatically discover Spark controllers over both Wifi and USB.
Note that the order in which controllers are discovered is not guaranteed. If you are using multiple Spark controllers, you will want to specify a device address or serial number.
The Spark service uses multiple arguments to determine how and where to find the Spark controller it should connect to. These arguments are:
The following diagram is a (simplified) display of the decision process to select a device. If discovery fails, the service reboots. This is because of a limitation in how Docker handles USB devices: the service must be started after the device was plugged in.
--device-host are the most specific arguments, and will take priority.
Note that device ID will not be checked when using these arguments.
spark-one: ... command: > --device-host=192.168.0.60
spark-one: ... command: > --device-serial=/dev/ttyACM0
--discovery has three possible values:
all is the default.
Because USB devices are more specific, they will always be checked first.
device-id is used to disqualify discovered devices. If
--device-id is not set, all discovered devices are valid.
The argument value is the unique serial number of your Spark controller. While your Spark controller is connected over USB, you can get its serial number by running the following command in your terminal:
docker run --rm --privileged brewblox/brewblox-devcon-spark:rpi-edge --list-devices
Example output (SER is the serial number):
pi@brewpipi:~/brewblox $ docker run --privileged brewblox/brewblox-devcon-spark:rpi-edge --list-devices 2019/02/01 10:41:05 INFO brewblox_service.service Creating [spark] application 2019/02/01 10:41:05 INFO __main__ Listing connected devices: 2019/02/01 10:41:05 INFO __main__ >> /dev/ttyACM0 | P1 - P1 Serial | USB VID:PID=2B04:C008 SER=300045000851353532343835 LOCATION=1-1.2:1.0
Specific device, over Wifi or USB:
spark-one: ... command: > --device-id=300045000851353532343835
Specific device, USB only:
spark-one: ... command: > --discovery=usb --device-id=300045000851353532343835
First discovered device, Wifi only:
spark-one: ... command: > --discovery=wifi