Kai Liu / Mbed 2 deprecated Nucleo_LoRaPHY

LoRaPHY project, based upon SX1276Lib, hardware with NUCLEO-F103EB/L053R8 and other boards as well as multiple Radio modules of SX1272/1276/1278. The code contains MACRO definitions and can be configured as TX/RX only, PINGPONG and consider to be a code base of RTTY.

Dependencies:   SX1276Lib mbed

Bugs

Table of Contents

  1. Bugs
  2. XTAL configuration
  3. PA channel
  4. TX timer overflow
  5. RX error

Bugs

  • XTAL configuration
  • PA channel
  • TX timer overflow
  • RX error

XTAL configuration

By default, the RF carrier is set to LF 434MHz with 32MHz external Crystal. The POR default value for RegFrfMsb/RegFrfMid/RegFrfLsb registers are 6C8000.

Due to unknown historical reason, the supplier of RFM100L released source code in a wrong RF carrier configuration. It seems to setup a carrier on 433MHz with 26MHz. However the module has 32MHz crystal on board, therefore its code is running on 532.92MHz, which beyond Semtech's specification for 525MHz for LF band.

PA channel

After carefully compare the schematics between official dev boards from Semtech and RF module manufacturers, we found out:

  • Semtech SX1276 use 14dBm RFO_LF/HF as RF output
  • SX1278 RF modules usually use 20dBm PA_BOOST pin as RF output

Therefore, if we reuse SX1276Lib, the receiver will get very weak signal around -120dBm, since it has no matching antenna at all.

TX timer overflow

If system timer to used to trigger TX mode, the system time must be reset, and keep it running after that reset. Otherwise the system timer will overflow about 30 minutes.

RX error

The STM32L053R8/mbed5 port shows up RX_TIMEOUT_OR_ERROR on terminal, while STM32F103RB/mbed2 doesn't show up such error at very beginning. And we found it is caused by CRC ERROR，something wrong with register setup. That was proved by synchronization of SX1276Lib.

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