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Some more explanation about spread factor in LoRaWAN #10

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Some more explanation about spread factor in LoRaWAN #10

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15 changes: 11 additions & 4 deletions docs/intro-to-lora.md
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Expand Up @@ -165,8 +165,8 @@ If you followed the installation steps in the LORIOT documentation, the binary w
* If you extracted the LORIOT binary somewhere else, edit the path.
* We're CDing into the folder first, otherwise LORIOT cannot find its certificate.

1. Make the file executable: `chmod +x /etc/init.d/start-loriot.sh`.
1. Link the script: `ln -s /etc/init.d/start-loriot.sh /etc/rc5.d/S99start-loriot.sh`.
1. Make the file executable: `chmod +x /etc/init.d/start-loriot.sh`
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Removed the dots because people copy this over wrong...

1. Link the script: `ln -s /etc/init.d/start-loriot.sh /etc/rc5.d/S99start-loriot.sh`
1. Now reboot the gateway and verify that the LORIOT binary is running (via `ps aux | grep loriot`).

#### Raspberry Pi and IMST iC880A
Expand All @@ -181,8 +181,15 @@ Now off to the interesting work: building a device that can send sensor data ove

### Some notes on writing firmware

1. You cannot send data constantly because of duty cycle limitations. This is a requirement of using the open spectrum. If you send too quickly, sending will fail.
1. A disadvantage of the LoRa shield is that it blocks all the pins. You can solder some new headers on the back of the shield to add new peripherals, or use a microcontroller like the nRF51-DK that has the pins available twice, once through hole connectors and once through female headers.
#### Sending data constantly

You cannot send data constantly because of duty cycle limitations. This is a requirement of using the open spectrum. If you send too quickly, sending will fail. How fast you are allowed to send depends on the spread factor that you use. With a higher spread factor it takes longer to send a message - although the chance that it will be received by a gateway increases - thus you'll need to wait longer before you can send again. During development you can set the spread factor to SF7 (the lowest) so you can send every 6-7 seconds.

LoRaWAN has a feature called Adaptive Data Rating (ADR) where the network can control the spread factor. You probably want this enabled.

#### Blocking pins

A disadvantage of the LoRa shield is that it blocks all the pins. You can solder some new headers on the back of the shield to add new peripherals, or use a microcontroller like the nRF51-DK that has the pins available twice, once through hole connectors and once through female headers.

### Registering the device on LORIOT

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