LoRa相关LPWAN设计

LoRaWAN HCI 草稿

2018-10-01  本文已影响6人  小鱼儿他老汉

从Bluetooth SIG和TI官网上下载了HCI规格书,参考并定义了LoRa/LoRaWAN的HCI规格。同时在STM32F401上使用MicroPython快速构建了对应的HCI Controller,并与现有的LoRaWAN网关驱动、LoRaWANPktFwd UDP服务器、MQTT代理服务器,以及自己的EPIC IoTHub进行了整合。

从市场营销角度,HCI Controller必须使用C/C++编程,这样可以实现最低成本。比如国产 CH430 + MCU(STM8) + SX127X,真的可以很便宜,还是等我以后来再做这个烂大街组合。但是从快速集成角度看,资源过于受限制的产品组合会导致非常长的周期,我还是顺手拿个MicroPython MCU来快速成型。

HCI Opcode

OpCode Binary Comment
Write_Addr FC06 SYS
Update_Baudrate FF36 SYS
Power_Mode_Config FD0C SYS
Clock_Set_Timeout FE24 SYS
Write_Codec_Config FD06 AVC
RF_Calibration FDFB PHY
Set_Power_Level FD82 PHY
Set_Test_TX FDCA PHY
Set_Test_RX FDCB PHY
Set_Test_TX_RX FDCC PHY
Set_Features FF26 DBG
Get_System_Status FE1F DBG
Read_RSSI_SNR FDFC DBG
Read_HW_Register FF00 MAC
Write_HW_Register FF01 MAC
Read_Mod_Write_Register FD09 MAC

暂时只是这些草稿,参考的是TI的Vendor Specific Command,和标准OGF/OCF有差异,可能有错误和遗漏,(至少缺乏了Data透传的定义)之后再订正和增补。

Linux BlueZ hcitool至少支持以下命令:

hcitool - HCI Tool ver 4.101
Usage:
        hcitool [options] <command> [command parameters]
Options:
        --help  Display help
        -i dev  HCI device
Commands:
        dev     Display local devices
        inq     Inquire remote devices
        scan    Scan for remote devices
        name    Get name from remote device
        info    Get information from remote device
        spinq   Start periodic inquiry
        epinq   Exit periodic inquiry
        cmd     Submit arbitrary HCI commands
        con     Display active connections
        cc      Create connection to remote device
        dc      Disconnect from remote device
        sr      Switch master/slave role
        cpt     Change connection packet type
        rssi    Display connection RSSI
        lq      Display link quality
        tpl     Display transmit power level
        afh     Display AFH channel map
        lp      Set/display link policy settings
        lst     Set/display link supervision timeout
        auth    Request authentication
        enc     Set connection encryption
        key     Change connection link key
        clkoff  Read clock offset
        clock   Read local or remote clock
        lescan  Start LE scan
        lewladd Add device to LE White List
        lewlrm  Remove device from LE White List
        lewlsz  Read size of LE White List
        lewlclr Clear LE White list
        lecc    Create a LE Connection
        ledc    Disconnect a LE Connection
        lecup   LE Connection Update

MicroPython Demo HCI代码

import pyb
import gc
import hci

led = pyb.LED(1)
usb = pyb.USB_VCP()
uart1 = pyb.UART(1, 9600)

def setup():
    print("MicroPython for LoRaWAN")
    print("Simulator of LoRaWAN HCI, STM32F401CE")
    
def hciCmdParser(data):
    print("HCI Command Parser:{}".format(data))
    # if...ifelse...ifelse...else
    
def loop():
    global led, usb, uart1
    if usb.any():
        usbline = usb.readline()
        hciCmdParser(usbline)
    
setup()
while True:
    loop()

因为这是一个Demo,主要就是hciCmdParser(data)来实现乒乓式的HCI收发。在实际工程中,需要考虑SPI驱动、LoRaWAN MAC/LLL、外部中断、定时器中断。

其中SPI/SX127X/LoRaWAN是主线程;USB_VCP已经隐含在MicroPython底层了,不需要使用线程;定时器和外部中断在MicroPython中不算是线程。其设计反而比MicroPython/ESP8266要简单。如果用C语言来做,还需要一些时间的。

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