LoRa
来自Jack's Lab
目录 |
1 Key Concepts
1.1 Spreading Factor
Note:
The Spreading Factor must be known in advance on both transmit and receive sides of the link as different spreading factors are orthogonal to each other
Spreading Factor 6:
- Set Spreading Factor = 6 in Reg_ModemConfig2
- The head must be set to Implicit mode
- Set the DetectionOptimize of Reg_LoRaDetectOptimize to value '0b101'
- Write 0x0C in the RegDetectionThreshold
1.2 Signal Bandwidth
Note:
The Spreading Factor must be known in advance on both transmit and receive sides of the link
1.3 Coding Rate
2 TX
- Static configuration registers can only be accessed in Sleep, Standby or FSTX mode
- The LoRa FIFO can only be filled in Standby mode
- Data TX is initiated by sending TX mode request
- Upon completion the TxDone interrupt is issued and the radio returns to Standby mode
- Following transmission the radio can be manually placed in Sleep mode or the FIFO refilled for subsequent TX operation
LoRa TX data FIFO filling:
- Set Reg_FifoAddrPtr to Reg_FifoTxBaseAddr
- Write PayloadLength bytes to the FIFO (Reg_Fifo)
Reg_Fifo 是 FIFO 的统一读写口,SPI 读写 Reg_Fifo,就会去 FIFO 内部地址为 Reg_FifoAddrPtr 的位置取放数据
TX_Modem 直接去 FIFO 地址为 Reg_FifoTxBaseAddr 的位置,取 PayloadLength 字节的数据
3 TX Power
1. Set Reg_PaConfig[7:7] to select PA output pin
- 0 to select RFO pin, Output power is limited to +14 dBm (25mW)
- 1 to select PA_BOOST pin, Output power is limited to +20 dBm (100mW)
2. Set Reg_PaConfig[6:4] to select max output power
- Pmax = 10.8 + 0.6 * MaxPower [dBm], valide when user select the RFO pin as the output
3. Set Reg_PaConfig[3:0] to select OutputPower
- Pout = Pmax - (15 - OutputPower) if PaSelect = 1 (RFO pin)
- Pout = 17 - (15 - OutputPower) if PaSelect = 1 (PA_BOOST pin)
4 Schematics
http://modtronix.com/prod/imod/inair4/inair4_r1_sch.pdf
5 Chip
5.1 SX1278
- http://www.semtech.com/wireless-rf/rf-transceivers/sx1278/
- http://www.semtech.com/images/datasheet/LoraLowEnergyDesign_STD.pdf
- http://www.semtech.com/images/datasheet/LoraDesignGuide_STD.pdf
- http://www.semtech.com/images/datasheet/AN1200.19_SX127x_RefDesign_STD.pdf
- http://www.semtech.com/images/datasheet/an120014-xo-guidance-lora-modulation.pdf
6 Reference
- http://www.semtech.com/wireless-rf/rf-transceivers/
- http://cpham.perso.univ-pau.fr/LORA/RPIgateway.html