工业物联网通讯中采用Lora模块的实践
2020-11-17 本文已影响0人
gaoshine
工业物联网通讯中采用Lora模块的实践
0.Lora通讯简介
LoRa 是LPWAN通信技术中的一种，是美国Semtech公司采用和推广的一种基于扩频技术的超远距离无线传输方案。这一方案改变了以往关于传输距离与功耗的折衷考虑方式，为用户提供一种简单的能实现远距离、长电池寿命、大容量的系统，进而扩展传感网络。目前，LoRa 主要在全球免费频段运行，包括433、868、915 MHz等。
LoRa技术具有远距离、低功耗（电池寿命长）、多节点、低成本的特性。
下图从灵敏度、链路预算、覆盖范围、传输速率、发送电流、待机电流、接收电流、2000mAh电池使用寿命、定位、抗干扰性、拓扑结构、最大终端连接数等参数上比较了Sigfox、LTE-M、ZigBee、WLAN、802.11ah和 LoRa的区别。
lora0.png
从以上的参数上看,无论是能耗,传输距离lora都有无比的优越性.在目前的窄带通讯中,5G的nbiot技术还不普及,也不免费,需要运营商基站支持,wifi通讯距离短,部署成本高,目前唯一突出的就是lora通讯.
1.lora通讯模块
主要是semtech的sx127x和sx126x系列，区别就是支持的频段、最大发射功率、扩频因子等不同。需要外加mcu，调试射频以及软件，下表总结了这些芯片的主要特性。
ra02.jpg
lora.jpg
sx127x 是SPI接口的，需要外接mcu，免去调试射频。
下面我们使用esp32和sx127x模块,搭建一套lora的通讯系统.
lora1.jpg
esp32使用micropython,esp32和sx127x的模块之间使用SPI接口连接,
ESP32.jpg
使用sx127x的python的库.
重点了解一下sx127x的调用参数:
from time import sleep
import gc
import config_lora
PA_OUTPUT_RFO_PIN = 0
PA_OUTPUT_PA_BOOST_PIN = 1
# registers
REG_FIFO = 0x00
REG_OP_MODE = 0x01
REG_FRF_MSB = 0x06
REG_FRF_MID = 0x07
REG_FRF_LSB = 0x08
REG_PA_CONFIG = 0x09
REG_LNA = 0x0c
REG_FIFO_ADDR_PTR = 0x0d
REG_FIFO_TX_BASE_ADDR = 0x0e
FifoTxBaseAddr = 0x00
# FifoTxBaseAddr = 0x80
REG_FIFO_RX_BASE_ADDR = 0x0f
FifoRxBaseAddr = 0x00
REG_FIFO_RX_CURRENT_ADDR = 0x10
REG_IRQ_FLAGS_MASK = 0x11
REG_IRQ_FLAGS = 0x12
REG_RX_NB_BYTES = 0x13
REG_PKT_RSSI_VALUE = 0x1a
REG_PKT_SNR_VALUE = 0x1b
REG_MODEM_CONFIG_1 = 0x1d
REG_MODEM_CONFIG_2 = 0x1e
REG_PREAMBLE_MSB = 0x20
REG_PREAMBLE_LSB = 0x21
REG_PAYLOAD_LENGTH = 0x22
REG_FIFO_RX_BYTE_ADDR = 0x25
REG_MODEM_CONFIG_3 = 0x26
REG_RSSI_WIDEBAND = 0x2c
REG_DETECTION_OPTIMIZE = 0x31
REG_DETECTION_THRESHOLD = 0x37
REG_SYNC_WORD = 0x39
REG_DIO_MAPPING_1 = 0x40
REG_VERSION = 0x42
# modes
MODE_LONG_RANGE_MODE = 0x80 # bit 7: 1 => LoRa mode
MODE_SLEEP = 0x00
MODE_STDBY = 0x01
MODE_TX = 0x03
MODE_RX_CONTINUOUS = 0x05
MODE_RX_SINGLE = 0x06
# PA config
PA_BOOST = 0x80
# IRQ masks
IRQ_TX_DONE_MASK = 0x08
IRQ_PAYLOAD_CRC_ERROR_MASK = 0x20
IRQ_RX_DONE_MASK = 0x40
IRQ_RX_TIME_OUT_MASK = 0x80
# Buffer size
MAX_PKT_LENGTH = 255
class SX127x:
# The controller can be ESP8266, ESP32, Raspberry Pi, or a PC.
# The controller needs to provide an interface consisted of:
# 1. a SPI, with transfer function.
# 2. a reset pin, with low(), high() functions.
# 3. IRQ pinS , to be triggered by RFM96W's DIO0~5 pins. These pins each has two functions:
# 3.1 set_handler_for_irq_on_rising_edge()
# 3.2 detach_irq()
# 4. a function to blink on-board LED.
def __init__(self,
name='SX127x',
parameters={'frequency': 433E6, 'tx_power_level': 2, 'signal_bandwidth': 125E3,
'spreading_factor': 8, 'coding_rate': 5, 'preamble_length': 8,
'implicitHeader': False, 'sync_word': 0x12, 'enable_CRC': False},
onReceive=None):
self.name = name
self.parameters = parameters
self._onReceive = onReceive
self._lock = False
def init(self, parameters=None):
if parameters: self.parameters = parameters
# check version
version = self.readRegister(REG_VERSION)
if version != 0x12:
raise Exception('Invalid version.')
# put in LoRa and sleep mode
self.sleep()
# config
self.setFrequency(self.parameters['frequency'])
self.setSignalBandwidth(self.parameters['signal_bandwidth'])
# set LNA boost
self.writeRegister(REG_LNA, self.readRegister(REG_LNA) | 0x03)
# set auto AGC
self.writeRegister(REG_MODEM_CONFIG_3, 0x04)
self.setTxPower(self.parameters['tx_power_level'])
self._implicitHeaderMode = None
self.implicitHeaderMode(self.parameters['implicitHeader'])
self.setSpreadingFactor(self.parameters['spreading_factor'])
self.setCodingRate(self.parameters['coding_rate'])
self.setPreambleLength(self.parameters['preamble_length'])
self.setSyncWord(self.parameters['sync_word'])
self.enableCRC(self.parameters['enable_CRC'])
# set LowDataRateOptimize flag if symbol time > 16ms (default disable on reset)
# self.writeRegister(REG_MODEM_CONFIG_3, self.readRegister(REG_MODEM_CONFIG_3) & 0xF7) # default disable on reset
if 1000 / (self.parameters['signal_bandwidth'] / 2 ** self.parameters['spreading_factor']) > 16:
self.writeRegister(REG_MODEM_CONFIG_3, self.readRegister(REG_MODEM_CONFIG_3) | 0x08)
# set base addresses
self.writeRegister(REG_FIFO_TX_BASE_ADDR, FifoTxBaseAddr)
self.writeRegister(REG_FIFO_RX_BASE_ADDR, FifoRxBaseAddr)
self.standby()
def beginPacket(self, implicitHeaderMode=False):
self.standby()
self.implicitHeaderMode(implicitHeaderMode)
# reset FIFO address and paload length
self.writeRegister(REG_FIFO_ADDR_PTR, FifoTxBaseAddr)
self.writeRegister(REG_PAYLOAD_LENGTH, 0)
def endPacket(self):
# put in TX mode
self.writeRegister(REG_OP_MODE, MODE_LONG_RANGE_MODE | MODE_TX)
# wait for TX done, standby automatically on TX_DONE
while (self.readRegister(REG_IRQ_FLAGS) & IRQ_TX_DONE_MASK) == 0:
pass
# clear IRQ's
self.writeRegister(REG_IRQ_FLAGS, IRQ_TX_DONE_MASK)
self.collect_garbage()
def write(self, buffer):
currentLength = self.readRegister(REG_PAYLOAD_LENGTH)
size = len(buffer)
# check size
size = min(size, (MAX_PKT_LENGTH - FifoTxBaseAddr - currentLength))
# write data
for i in range(size):
self.writeRegister(REG_FIFO, buffer[i])
# update length
self.writeRegister(REG_PAYLOAD_LENGTH, currentLength + size)
return size
def aquire_lock(self, lock=False):
if not config_lora.IS_MICROPYTHON: # MicroPython is single threaded, doesn't need lock.
if lock:
while self._lock: pass
self._lock = True
else:
self._lock = False
def println(self, string, implicitHeader=False):
self.aquire_lock(True) # wait until RX_Done, lock and begin writing.
self.beginPacket(implicitHeader)
self.write(string.encode())
self.endPacket()
self.aquire_lock(False) # unlock when done writing
def getIrqFlags(self):
irqFlags = self.readRegister(REG_IRQ_FLAGS)
self.writeRegister(REG_IRQ_FLAGS, irqFlags)
return irqFlags
def packetRssi(self):
return (self.readRegister(REG_PKT_RSSI_VALUE) - (164 if self._frequency < 868E6 else 157))
def packetSnr(self):
return (self.readRegister(REG_PKT_SNR_VALUE)) * 0.25
def standby(self):
self.writeRegister(REG_OP_MODE, MODE_LONG_RANGE_MODE | MODE_STDBY)
def sleep(self):
self.writeRegister(REG_OP_MODE, MODE_LONG_RANGE_MODE | MODE_SLEEP)
def setTxPower(self, level, outputPin=PA_OUTPUT_PA_BOOST_PIN):
if (outputPin == PA_OUTPUT_RFO_PIN):
# RFO
level = min(max(level, 0), 14)
self.writeRegister(REG_PA_CONFIG, 0x70 | level)
else:
# PA BOOST
level = min(max(level, 2), 17)
self.writeRegister(REG_PA_CONFIG, PA_BOOST | (level - 2))
def setFrequency(self, frequency):
self._frequency = frequency
frfs = {169E6: (42, 64, 0),
433E6: (108, 64, 0),
434E6: (108, 128, 0),
866E6: (216, 128, 0),
868E6: (217, 0, 0),
915E6: (228, 192, 0)}
self.writeRegister(REG_FRF_MSB, frfs[frequency][0])
self.writeRegister(REG_FRF_MID, frfs[frequency][1])
self.writeRegister(REG_FRF_LSB, frfs[frequency][2])
def setSpreadingFactor(self, sf):
sf = min(max(sf, 6), 12)
self.writeRegister(REG_DETECTION_OPTIMIZE, 0xc5 if sf == 6 else 0xc3)
self.writeRegister(REG_DETECTION_THRESHOLD, 0x0c if sf == 6 else 0x0a)
self.writeRegister(REG_MODEM_CONFIG_2, (self.readRegister(REG_MODEM_CONFIG_2) & 0x0f) | ((sf << 4) & 0xf0))
def setSignalBandwidth(self, sbw):
bins = (7.8E3, 10.4E3, 15.6E3, 20.8E3, 31.25E3, 41.7E3, 62.5E3, 125E3, 250E3)
bw = 9
for i in range(len(bins)):
if sbw <= bins[i]:
bw = i
break
# bw = bins.index(sbw)
self.writeRegister(REG_MODEM_CONFIG_1, (self.readRegister(REG_MODEM_CONFIG_1) & 0x0f) | (bw << 4))
def setCodingRate(self, denominator):
denominator = min(max(denominator, 5), 8)
cr = denominator - 4
self.writeRegister(REG_MODEM_CONFIG_1, (self.readRegister(REG_MODEM_CONFIG_1) & 0xf1) | (cr << 1))
def setPreambleLength(self, length):
self.writeRegister(REG_PREAMBLE_MSB, (length >> 8) & 0xff)
self.writeRegister(REG_PREAMBLE_LSB, (length >> 0) & 0xff)
def enableCRC(self, enable_CRC=False):
modem_config_2 = self.readRegister(REG_MODEM_CONFIG_2)
config = modem_config_2 | 0x04 if enable_CRC else modem_config_2 & 0xfb
self.writeRegister(REG_MODEM_CONFIG_2, config)
def setSyncWord(self, sw):
self.writeRegister(REG_SYNC_WORD, sw)
# def enable_Rx_Done_IRQ(self, enable = True):
# if enable:
# self.writeRegister(REG_IRQ_FLAGS_MASK, self.readRegister(REG_IRQ_FLAGS_MASK) & ~IRQ_RX_DONE_MASK)
# else:
# self.writeRegister(REG_IRQ_FLAGS_MASK, self.readRegister(REG_IRQ_FLAGS_MASK) | IRQ_RX_DONE_MASK)
# def dumpRegisters(self):
# for i in range(128):
# print("0x{0:02x}: {1:02x}".format(i, self.readRegister(i)))
def implicitHeaderMode(self, implicitHeaderMode=False):
if self._implicitHeaderMode != implicitHeaderMode: # set value only if different.
self._implicitHeaderMode = implicitHeaderMode
modem_config_1 = self.readRegister(REG_MODEM_CONFIG_1)
config = modem_config_1 | 0x01 if implicitHeaderMode else modem_config_1 & 0xfe
self.writeRegister(REG_MODEM_CONFIG_1, config)
def onReceive(self, callback):
self._onReceive = callback
if self.pin_RxDone:
if callback:
self.writeRegister(REG_DIO_MAPPING_1, 0x00)
self.pin_RxDone.set_handler_for_irq_on_rising_edge(handler=self.handleOnReceive)
else:
self.pin_RxDone.detach_irq()
def receive(self, size=0):
self.implicitHeaderMode(size > 0)
if size > 0: self.writeRegister(REG_PAYLOAD_LENGTH, size & 0xff)
# The last packet always starts at FIFO_RX_CURRENT_ADDR
# no need to reset FIFO_ADDR_PTR
self.writeRegister(REG_OP_MODE, MODE_LONG_RANGE_MODE | MODE_RX_CONTINUOUS)
# on RPi, interrupt callback is threaded and racing with main thread,
# Needs a lock for accessing FIFO.
# https://sourceforge.net/p/raspberry-gpio-python/wiki/Inputs/
# http://raspi.tv/2013/how-to-use-interrupts-with-python-on-the-raspberry-pi-and-rpi-gpio-part-2
def handleOnReceive(self, event_source):
self.aquire_lock(True) # lock until TX_Done
# irqFlags = self.getIrqFlags() should be 0x50
if (self.getIrqFlags() & IRQ_PAYLOAD_CRC_ERROR_MASK) == 0:
if self._onReceive:
payload = self.read_payload()
self.aquire_lock(False) # unlock when done reading
self._onReceive(self, payload)
self.aquire_lock(False) # unlock in any case.
def receivedPacket(self, size=0):
irqFlags = self.getIrqFlags()
self.implicitHeaderMode(size > 0)
if size > 0: self.writeRegister(REG_PAYLOAD_LENGTH, size & 0xff)
# if (irqFlags & IRQ_RX_DONE_MASK) and \
# (irqFlags & IRQ_RX_TIME_OUT_MASK == 0) and \
# (irqFlags & IRQ_PAYLOAD_CRC_ERROR_MASK == 0):
if (irqFlags == IRQ_RX_DONE_MASK): # RX_DONE only, irqFlags should be 0x40
# automatically standby when RX_DONE
return True
elif self.readRegister(REG_OP_MODE) != (MODE_LONG_RANGE_MODE | MODE_RX_SINGLE):
# no packet received.
# reset FIFO address / # enter single RX mode
self.writeRegister(REG_FIFO_ADDR_PTR, FifoRxBaseAddr)
self.writeRegister(REG_OP_MODE, MODE_LONG_RANGE_MODE | MODE_RX_SINGLE)
def read_payload(self):
# set FIFO address to current RX address
# fifo_rx_current_addr = self.readRegister(REG_FIFO_RX_CURRENT_ADDR)
self.writeRegister(REG_FIFO_ADDR_PTR, self.readRegister(REG_FIFO_RX_CURRENT_ADDR))
# read packet length
packetLength = self.readRegister(REG_PAYLOAD_LENGTH) if self._implicitHeaderMode else \
self.readRegister(REG_RX_NB_BYTES)
payload = bytearray()
for i in range(packetLength):
payload.append(self.readRegister(REG_FIFO))
self.collect_garbage()
return bytes(payload)
def readRegister(self, address, byteorder='big', signed=False):
response = self.transfer(self.pin_ss, address & 0x7f)
return int.from_bytes(response, byteorder)
def writeRegister(self, address, value):
self.transfer(self.pin_ss, address | 0x80, value)
def collect_garbage(self):
gc.collect()
if config_lora.IS_MICROPYTHON:
print('[Memory - free: {} allocated: {}]'.format(gc.mem_free(), gc.mem_alloc()))
发送消息代码:
"""
@project lola sx127x模块通讯测试
@File : rola main.py
@Contact : gaoshine2008@qq.com
@License : (C)Copyright 2018-2022, 金世达科技.微妙物联
@Modify Time @Author @Version @Desciption
------------ ------- -------- -----------
10/16/20 10:03 GAOSHENG 1.0 we.iot
"""
import sx127x
import config_lora
from time import sleep
import gc
def send(lora):
counter = 0
print("LoRa Sender")
while True:
msg = input('input')
payload = msg
print("Sending packet: \n{}\n".format(payload))
lora.println(payload)
counter += 1
sleep(5)
def receive(lora):
print("LoRa Receiver")
while True:
if lora.receivedPacket():
lora.blink_led()
try:
payload = lora.read_payload()
print("*** Received message ***\n{}".format(payload.decode()))
except Exception as e:
print(e)
print("with RSSI: {}\n".format(lora.packetRssi))
def dumpRegisters(lora):
lora.dumpRegisters()
def main():
gc.collect()
controller = config_lora.Controller()
lora = controller.add_transceiver(sx127x.SX127x(name='LoRa'),
pin_id_ss=config_lora.Controller.PIN_ID_FOR_LORA_SS,
pin_id_RxDone=config_lora.Controller.PIN_ID_FOR_LORA_DIO0)
print('lora', lora)
send(lora)
if __name__ == '__main__':
main()
接收消息代码:
"""
@project lola sx127x模块通讯测试
@File : rola main.py
@Contact : gaoshine2008@qq.com
@License : (C)Copyright 2018-2022, 金世达科技.微妙物联
@Modify Time @Author @Version @Desciption
------------ ------- -------- -----------
10/16/20 10:03 GAOSHENG 1.0 we.iot
"""
from machine import UART
import sx127x
import config_lora
from time import sleep
import gc
m5_ser = UART(1)
def sendtom5(msg):
print("Send msg to M5")
m5_ser.write(msg)
m5_ser.write(b';\n\r')
return True
def receive(lora):
print("LoRa Receiver")
while True:
if lora.receivedPacket():
lora.blink_led()
try:
payload = lora.read_payload()
msg = payload.decode()
print("*** Received message ***\n{}".format(payload.decode()))
r = sendtom5(msg)
except Exception as e:
print(e)
print("with RSSI: {}\n".format(lora.packetRssi))
def dumpRegisters(lora):
lora.dumpRegisters()
def main():
gc.collect()
controller = config_lora.Controller()
lora = controller.add_transceiver(sx127x.SX127x(name='LoRa'),
pin_id_ss=config_lora.Controller.PIN_ID_FOR_LORA_SS,
pin_id_RxDone=config_lora.Controller.PIN_ID_FOR_LORA_DIO0)
print('lora', lora)
receive(lora)
if __name__ == '__main__':
main()
