Lora_Pico_Driver

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Description

The Lora_Pico_Driver project is an open source project based on the Raspberry Pi Pico, Lora Radio, and freeRTOS. It's goal is to give hobbyists and developers a strong starting point for their projects involving Lora. This project is the PHY layer of the Lora modem, with LoraWAN functionality coming soon.

Functionality

An open driver for Lora on a Raspberry Pi Pico would not easily allow for the expansion of an application. Adding freeRTOS to the Raspberry Pi Pico allows an application developer to easily create new functionalities. For example, it would be challenging to add a new sensor to a sensor array with Lora in a single superloop, but with freeRTOS we can create a new task, or individually addressable superloop, that interacts with the Lora task independently of the original sensor array. In this project there are three tasks, and main():

1. vSimpleLEDTask is a few lines to show the structure of a task with the setup being above the infinite loop, and the blinking of the onboard pico LED to show the action of the infinite loop.
2. vUsbIOTask which takes input from a serial monitor over usb using getchar(). A 0x00 or NULL is appended to the end of the unsigned 8 bit pointer array used as a dynamic ascii character array for a NULL terminated 'string'. The address of the pointer array is then sent to vSx1280Task for sending through the sx1280.
3. vSx1280Task will take the pointer array from vUsbIOTask through a Task Notification and reassign the pointer to a task local pointer array. This is done because there are functions called which delays vSx1280Task and would allow vUsbIOTask to overwrite the Task Notification pointer array. Once the data is task local vSx1280Task will perform a Tx operation, followed by an Rx operation. Both operations are done by using the sx1280Setup, sx1280Tx, and sx1280Rx functions, also in main.c.

File Structure

The file structure of this project is dictated by the use of the C/C++ SDK offered by Raspberry Pi, and by freeRTOS. The files CMakeLists.txt, and pico_sdk_import.cmake come from the C/C++ SDK, the file include/FreeRTOSConfig.h, and the directory FreeRTOS-Kernel come from the use of freeRTOS. If you have not, I encourage you to go through the getting started with pico documentation to set up your coding environment. The directory tree should resemble the list below:

• pico_projects
  • pico_sdk
  • Lora_Pico_driver
    • docs
    • FreeRTOS-Kernel
      • include
        • FreeRTOSConfig.h
    • src
      • main.c
    • CMakeLists.txt
    • pico_sdk_import.cmake
    • FreeRTOS_Kernel_import.cmake

How To Use

This project is not meant to be used as a library, instead it's a template to begin a given project involving a Raspberry Pi Pico, and Lora Modem. In the vSx1280Task you will find an example of how to send and receive message packets over 2.4GHz Lora. This example even includes input over usb through a serial monitor which is included in an outbound message. I encourage you to add sensors, or displays and create your own long range wireless Internet of Things network.

There are two ways of using this project:

1. Creating functions to handle new hardware, and using them in vSx1280Task
2. Creating a task to handle new hardware with functions used in the newly written task

The second method is recomended, as it is more dynamic and easier to debug. Once downloaded however, it is your code with which you may do as you please.

Given a new task has been created to handle new hardware there must be communication between tasks. Thats where freeRTOS Task Notifications come in. They are fast and easy to use for sending data between task in a memory efficient manner. In your new task you should create an 8 bit pointer array to store data in an sx1280 message compatible format:

uint8_t *dataBuffer = 0;

Allocate the appropriate amount of memory, in 8 bit chunks, that you'll need to send your data:

dataBuffer = ( uint8_t * ) malloc( 256 * sizeof( uint8_t ) );

Here 256 is being used because that is the maximum Lora packet size on the sx1280.
Assign your data to the newly allocated data buffer:

*( dataBuffer + 0 ) = 0x48; // 0x48 is ASCII Hexadecimal 'H' 
*( dataBuffer + 1 ) = 0x49; // 0x49 is ASCII Hexadecimal 'I'

Use the xTaskNotify() function to send a task notification from your new task to vSx1280Task:

xTaskNotify(  
            xSx1280TaskHandle,                  /* TaskHandle_t xTaskToNotify */  
            ( uint32_t ) &*( dataBuffer ),      /* uint32_t ulValue (int)&buffer[0] */  
            eSetValueWithoutOverwrite );        /* eNotifyAction eAction */  
           )

In vSx1280Task the xTaskNotifyWait() will accept Task Notifications from all tasks that are sending them. You must process the current Task Notification before allowing another task to run or the current Task Notification may be overwritten by an incoming Task Notification from another task.