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commit 6f1edad8f58f5efaa078f2c2a068c51a800a5f67 Author: Arjav Patel <[email protected]> AuthorDate: Sat Mar 7 03:48:45 2026 +0530 docs/examples/sx127x_demo: Expand SX127X demo documentation Add default configuration, short-range FSK testing tips, and troubleshooting guidance for the SX127X demo example. Signed-off-by: Arjav Patel <[email protected]> --- .../applications/examples/sx127x_demo/index.rst | 65 ++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/Documentation/applications/examples/sx127x_demo/index.rst b/Documentation/applications/examples/sx127x_demo/index.rst index 7e3cc329c96..3512e266865 100644 --- a/Documentation/applications/examples/sx127x_demo/index.rst +++ b/Documentation/applications/examples/sx127x_demo/index.rst @@ -3,3 +3,68 @@ ============================ This example demonstrates the use of the ``SX127X`` radio. + +Overview +======== + +The ``sx127x_demo`` application exercises the `SX127X` low-power wide-area +network (LPWAN) radio driver in both transmit and receive modes. It is +typically enabled via a board defconfig together with +``CONFIG_LPWAN_SX127X`` and the appropriate SPI and GPIO wiring for the +target module. + +Default configuration +===================== + +Unless explicitly overridden in the board or application configuration, +the SX127X driver uses the following relevant defaults: + +* RF frequency: ``CONFIG_LPWAN_SX127X_RFFREQ_DEFAULT`` (board-specific, + for example 433 MHz, 868 MHz or 915 MHz). +* TX power: ``CONFIG_LPWAN_SX127X_TXPOWER_DEFAULT``. + The global default is **17 dBm**, which provides a stronger and more + reliable link than the previous 14 dBm default. +* CRC: ``CONFIG_LPWAN_SX127X_CRCON``. + The global default is **1** (CRC enabled), so payloads are protected + by a checksum and corrupted frames are rejected. + +Individual boards may override these values in their ``defconfig`` files. +For example, some boards tested with integrated SX1276 modules may set +``CONFIG_LPWAN_SX127X_TXPOWER_DEFAULT=20`` and adjust +``CONFIG_LPWAN_SX127X_RFFREQ_DEFAULT`` to match the module’s band. + +Short-range FSK testing +======================= + +When running short-range FSK tests (for example, two modules placed +around one meter apart on a lab bench), the following settings are +recommended: + +* Keep ``CONFIG_LPWAN_SX127X_TXPOWER_DEFAULT`` at **17 dBm** or higher + (some modules work well at 20 dBm) to avoid marginal RSSI values that + can lead to intermittent reception. +* Ensure ``CONFIG_LPWAN_SX127X_CRCON=1`` on both transmitter and + receiver so corrupted frames are discarded instead of being printed + with incorrect data. + +These defaults are based on empirical testing reported by users and are +intended to provide robust communication without requiring additional +per-board tuning. + +Troubleshooting +=============== + +If the receiver occasionally shows no data, truncated data, or payloads +that do not match what was transmitted, check the following: + +* Verify that the RF frequency and modulation settings are identical on + both sides. +* Inspect the reported RSSI and SNR values; very low RSSI at short + distance can indicate insufficient TX power or antenna issues. +* Confirm that CRC is enabled and that both peers are configured + consistently (either both with CRC enabled or both with it disabled, + though enabling CRC is recommended). + +Adjusting TX power or antenna placement and ensuring consistent CRC +settings on the link typically resolves data integrity problems seen in +simple FSK tests.
