fix: enable LoRa CRC on SX127x for RNode interop#45
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After reset, SX127x hardware leaves REG_MODEM_CONFIG_2 bit 2 (RxPayloadCrcOn) cleared, and RadioLib's SX127x::begin() does not touch it. Upstream RNode firmware explicitly enables CRC on every LoRa transmit and receive path (sx127x::enableCrc in RNode_Firmware.ino:531, sx127x.cpp:160), so a real RNode will silently drop frames that arrive without a valid CRC. This means T-Beam and LoRa32 V2.1 users running the example LoRaInterface cannot interop with real RNodes over LoRa today: outbound packets are dropped at the RNode, inbound packets may be accepted but silently corrupted. Fix by calling chip->setCRC(true) after SX1276::begin() in the SX127x branch of LoRaInterface::start(). The new call is gated on the prior begin() having succeeded, and its own error is folded into state so the existing RADIOLIB_ERR_NONE check catches it. No change required on the SX126x branches: RadioLib's SX126x::begin() already calls setCRC(2), so RAK4631, Heltec V3, and Heltec V4 inherit CRC-on.
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Many thanks for the patch. |
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Summary
Enable LoRa CRC in the SX127x branch of the example
LoRaInterface.Without this, T-Beam and LoRa32 V2.1 boards running microReticulum
cannot interoperate with real RNode hardware: outbound frames are
silently dropped at the RNode, and inbound frames lack the CRC check
that Arduino-LoRa-era receivers used to rely on.
Why
After reset,
REG_MODEM_CONFIG_2bit 2 (RxPayloadCrcOn) on SX127xis
0, andSX127x::begin()does not touch it.SX127x::config()only disables frequency hopping. So CRC stays off.
Upstream RNode firmware explicitly enables CRC on SX127x:
RNode_Firmware/RNode_Firmware.ino:531:LoRa->enableCrc();RNode_Firmware/sx127x.cpp:160:enableCrc();called from theequivalent of
begin().So any peer speaking the RNode wire format expects a CRC on every
LoRa frame and drops those that arrive without one. microReticulum's
example interface needs to match that expectation.
What changed
One file, inside
LoRaInterface::start()in theBOARD_TBEAM / BOARD_LORA32_V21branch, immediately afterchip->begin(...):Gated on the prior
begin()having succeeded; its own return valueis folded into
stateso the existingRADIOLIB_ERR_NONEcheckbelow catches a CRC-enable failure too.
Not changed
SX126x branches (RAK4631, Heltec V3, Heltec V4) are untouched.
RadioLib's
SX126x::begin()already callssetCRC(2)internally(
SX126x.cpp:61,114), so those boards inherit CRC-on by default.Adding an explicit call there would be defensive but noisy; happy to
add it if you prefer.
Test plan
announces that a real RNode (or Python RNS with
RNodeInterface) receives and delivers into transport.microReticulum node.
and interoperate unchanged.
Note: this PR was prepared with the help of generative AI as part of work on the RTReticulum project. While the problem was manually identified, the patch, commit message, and this description were drafted by an AI assistant and reviewed by a human before submission.