Help Debugging RadioLib Init (-2 Error) on XIAO S3 + Wio-SX1262 (Meshtastic Works!)

[rallep71]

Hi RadioLib Community

I'm facing a persistent issue trying to get a minimal RadioLib sketch working on a Seeed Studio XIAO ESP32-S3 connected to a Wio-SX1262 LoRa module via the B2B connector. The strange thing is that Meshtastic firmware runs perfectly fine on this exact hardware setup, sending and receiving packets.

However, when I try to run even the most basic RadioLib initialization sketch (just calling radio.begin()), it consistently fails with error code -2 (RADIOLIB_ERR_CHIP_NOT_FOUND).

Hardware & Confirmed Pinout:

• Board: Seeed Studio XIAO ESP32-S3
• LoRa Module: Wio-SX1262 (B2B Connector)
• Pinout (Confirmed via Meshtastic platformio.ini and pins_arduino.h for seeed_xiao_esp32s3):
  • SCK: GPIO 36
  • MISO: GPIO 37
  • MOSI: GPIO 35
  • NSS: GPIO 7
  • RESET: GPIO 4
  • DIO1: GPIO 1
  • BUSY: GPIO 2
• TCXO Voltage: 1.8V (Confirmed via Meshtastic platformio.ini and Wio-SX1262 Datasheet)
• Regulator: DC-DC (Confirmed via Wio-SX1262 Datasheet)

What I've Tried in Minimal Sketches:

(Using PlatformIO with latest stable ESP32 Core & RadioLib v7.1.2 / v6.5.0)

• Using the confirmed Pinout 1 (see above).
• Performing specific manual reset sequences before SPI/Radio init (digitalWrite(RST, LOW); delay(50); digitalWrite(RST, HIGH); delay(200);).
• Setting SPI frequency explicitly (e.g., 1 MHz).
• Using the radio.begin() variant that explicitly sets the TCXO voltage (1.8f).
• Tried radio.begin() variants forcing LDO mode (just in case, though datasheet says DC-DC).
• Ensured SPI is initialized before radio.begin().
• Tested with both latest RadioLib (v7.1.2) and an older one (v6.5.0).

The core issue remains: radio.begin() fails with -2.

Since Meshtastic works flawlessly, it strongly suggests there's some crucial pre-initialization step, specific GPIO configuration (pull-ups/downs?), power management setup, or a subtle RadioLib configuration detail that Meshtastic performs for the XIAO ESP32-S3 + Wio-SX1262 combo, which is missing in a standard minimal RadioLib example.

My Question:

Could anyone familiar with the Meshtastic codebase for the seeed_xiao_esp32s3 variant shed some light on what specific initialization steps or configurations Meshtastic applies before or during the RadioLib initialization that might be critical for the SX1262 chip to be detected correctly on this hardware? Any pointers to the relevant sections in the Meshtastic source code (e.g., specific functions in src/variants/ or elsewhere) would be greatly appreciated!

Thanks in advance for any help!

Minimal Failing Example (PlatformIO main.cpp):

#include <Arduino.h>
#include <SPI.h>
#include <RadioLib.h>

// === Pinout 1 (Forum - Wahrscheinlich korrekt) ===
// Direkt hier definiert, um Probleme mit build_flags zu umgehen
#define LORA_NSS_PIN   7   // GPIO 7
#define LORA_DIO1_PIN  1   // GPIO 1
#define LORA_RESET_PIN 4   // GPIO 4
#define LORA_BUSY_PIN  2   // GPIO 2
#define LORA_SCLK_PIN  36  // GPIO 36
#define LORA_MISO_PIN  37  // GPIO 37
#define LORA_MOSI_PIN  35  // GPIO 35

// === RadioLib Modul Instanz (Pins aus #define oben) ===
SX1262 radio = new Module(LORA_NSS_PIN, LORA_DIO1_PIN, LORA_RESET_PIN, LORA_BUSY_PIN);

// TCXO Spannung aus build_flags Makro holen (dieses Makro sollte noch funktionieren)
#ifdef RADIO_TCXO_VOLTAGE
  const float tcxoVoltage = RADIO_TCXO_VOLTAGE;
#else
  #warning "RADIO_TCXO_VOLTAGE not defined in build_flags, using default 1.8V"
  const float tcxoVoltage = 1.8; // Hardcode fallback
#endif


int packetCounter = 0; // Zähler für gesendete Pakete

void setup() {
  Serial.begin(115200);
  delay(2000); // Warte auf Serielle Verbindung
  Serial.println();
  Serial.println("=====================================");
  Serial.println("PlatformIO RadioLib SX1262 Test - v3 (Pins in Code, TCXO Explicit)");
  Serial.println("=====================================");

  // --- Manueller Reset (Spezifisches Timing) ---
  Serial.println("Performing manual reset (Pin GPIO " + String(LORA_RESET_PIN) + ", 50ms LOW, 200ms wait)...");
  pinMode(LORA_RESET_PIN, OUTPUT);
  digitalWrite(LORA_RESET_PIN, LOW);
  delay(50);
  digitalWrite(LORA_RESET_PIN, HIGH);
  delay(200);
  Serial.println("Manual reset done.");

  // --- SPI Initialisierung (mit Pinout 1 #defines) ---
  Serial.print("Initializing SPI with SCK=");
  Serial.print(LORA_SCLK_PIN);
  Serial.print(", MISO=");
  Serial.print(LORA_MISO_PIN);
  Serial.print(", MOSI=");
  Serial.println(LORA_MOSI_PIN);

  // Sicherer mit expliziten Pins
  SPI.begin(LORA_SCLK_PIN, LORA_MISO_PIN, LORA_MOSI_PIN);

  // --- Setze SPI Frequenz ---
  unsigned long spiFrequency = 1000000; // 1 MHz
  Serial.print("Setting SPI frequency to 1 MHz...");
  SPI.setFrequency(spiFrequency);
  Serial.println(" Done.");
  delay(50);

  // --- LoRa Radio Initialisierung mit explizitem TCXO ---
  Serial.print("Initializing SX1262 (Pinout 1) with TCXO=");
  Serial.print(tcxoVoltage);
  Serial.print("V, Default Regulator (DC-DC)... ");

  int state = radio.begin(868.1, 125.0, 7, 5, RADIOLIB_SX126X_SYNC_WORD_PUBLIC, 14, 8, tcxoVoltage);

  if (state == RADIOLIB_ERR_NONE) {
    Serial.println("\n**************************************");
    Serial.println("********** SUCCESS! Chip found! **********");
    Serial.println("**************************************");
    // Stop here for minimal test
    while(true);
  } else {
    Serial.print("FAILED! Chip not found or basic init failed, error code: ");
    Serial.println(state);
    Serial.println("Überprüfe #define Pins, TCXO, oder B2B-Kontakt.");
    while (true); // Stopp nach dem Test bei Fehler
  }
}

void loop() {
  // Empty for this minimal test
}

[jgromes]

I don't have experience with that specific board, but there is one thing that seems odd - you are initializing the SPI with what I assume are non-default SPI pins. However, in Module constructor, you have not specified a non-default SPI instance. This means that when you call radio.begin, RadioLib will try to initialize SPI with SPI.begin(), so it's getting called twice. I don't know how the ESP32 handles that, but it seems suspicious. See this wiki page on non-default SPI setups.

Otherwise, I would also enable debug logging at SPI level. That will at least let us know if the device returns some data.

[rallep71]

Hi everyone,

I'm at my wit's end trying to get a minimal RadioLib sketch to detect the SX1262 chip on a Seeed Studio XIAO ESP32-S3 connected via B2B connector to a Wio-SX1262 LoRa module. The baffling part is that Meshtastic firmware runs perfectly fine on this exact hardware, indicating the hardware itself (pins, module, antenna) is functional.

However, every attempt to initialize RadioLib in a minimal sketch (using PlatformIO) consistently fails with Error code: -2 (RADIOLIB_ERR_CHIP_NOT_FOUND).

Confirmed Hardware & Configuration (Based on Meshtastic Configs & Datasheets):

• Board: Seeed Studio XIAO ESP32-S3
• LoRa Module: Wio-SX1262 (B2B Connector)
• Pinout (Pinout 1 - Confirmed via Meshtastic):
  • SCK: GPIO 36
  • MISO: GPIO 37
  • MOSI: GPIO 35
  • NSS: GPIO 7
  • RESET: GPIO 4
  • DIO1: GPIO 1
  • BUSY: GPIO 2
  • PWR_EN: GPIO 5 (Power Enable for Wio module)
• TCXO Voltage: 1.8V
• Regulator: DC-DC (Module Default)

Extensive Troubleshooting Steps Taken (All Failed with Error -2):

• Verified Pinout 1 against Meshtastic configuration files.
• Used the correct RadioLib Module constructor, passing the SPI object and SPISettings explicitly (as recommended by jgromes).
• Tried various SPISettings (2MHz, 8MHz, SPI_MODE0, MSBFIRST).
• Implemented specific manual reset sequences with longer delays (100ms LOW, 500ms HIGH).
• Crucially: Explicitly activated the PWR_EN pin (GPIO 5) before any other initialization.
• Set appropriate pinMode for all relevant pins (NSS HIGH initially, BUSY/DIO1 INPUT, MISO INPUT_PULLUP tested).
• Used different radio.begin() variants (with/without explicit TCXO voltage parameter, with/without forcing LDO mode).
• Tested with different RadioLib versions (v7.1.2, v6.5.0).
• Used an up-to-date ESP32 Core via PlatformIO (platform = espressif32@^6.10.0).
• Performed Clean Build in PlatformIO multiple times.
• Confirmed basic serial communication works on the XIAO.
• Confirmed low-level SPI test fails to get a response (returns 0xFF or 0x00).

The Core Problem & Question:

Despite applying all known requirements (PWR_EN, correct pins, TCXO voltage, proper SPI initialization method for RadioLib), the SX1262 chip is never detected by radio.begin() in a minimal sketch, always returning error -2.

Since Meshtastic does work, it must be doing something fundamentally different during its initialization phase that we are missing. This could be:

1. A very specific, undocumented pre-initialization step for GPIOs or power rails on the XIAO S3 required before SPI or RadioLib init.
2. A subtle difference in how Meshtastic configures/uses the specific version of RadioLib or the ESP32 Core/Framework it depends on.
3. An unknown hardware quirk that Meshtastic implicitly handles.

Could anyone familiar with the Meshtastic (seeed_xiao_esp32s3 variant) or RadioLib integration shed light on what might be missing? Is there any other configuration (e.g., specific ESP32 component settings, different RadioLib function calls) that Meshtastic applies which could explain this discrepancy?

Any pointers or insights would be incredibly helpful!

Last Failing Code (PlatformIO):

platformio.ini:

[env:seeed_xiao_esp32s3]
platform = espressif32@^6.10.0 ; Using a recent version
board = seeed_xiao_esp32s3
framework = arduino
monitor_speed = 115200
upload_protocol = esptool
lib_deps =
    jgromes/RadioLib@^7.1.2 ; Tested also with 6.5.0

build_flags =
    -D RADIO_TCXO_VOLTAGE=1.8

#include <Arduino.h>
#include <SPI.h>
#include <RadioLib.h>

// Pinout 1 (Forum - Confirmed via Meshtastic Config)
#define LORA_NSS_PIN   7
#define LORA_DIO1_PIN  1
#define LORA_RESET_PIN 4
#define LORA_BUSY_PIN  2
#define LORA_SCLK_PIN  36
#define LORA_MISO_PIN  37
#define LORA_MOSI_PIN  35
#define LORA_PWR_EN_PIN 5 // Power Enable Pin

// SPISettings (Tried 2MHz and 8MHz)
SPISettings sx1262SpiSettings(8000000, MSBFIRST, SPI_MODE0); // 8 MHz

// RadioLib Module Instanz (Correct Constructor)
SX1262 radio = new Module(LORA_NSS_PIN, LORA_DIO1_PIN, LORA_RESET_PIN, LORA_BUSY_PIN, SPI, sx1262SpiSettings);

// TCXO Spannung aus build_flags
#ifdef RADIO_TCXO_VOLTAGE
  const float tcxoVoltage = RADIO_TCXO_VOLTAGE;
#else
  #warning "RADIO_TCXO_VOLTAGE not defined, using 1.8V"
  const float tcxoVoltage = 1.8;
#endif

void setup() {
  Serial.begin(115200);
  delay(2000);
  Serial.println("\n=====================================");
  Serial.println("PlatformIO RadioLib SX1262 Test - v13 (8MHz SPI, No TCXO in begin, MISO Pullup)");
  Serial.println("=====================================");

  // Schritt 1: Stromversorgung aktivieren
  Serial.print("Activating LORA_PWR_EN_PIN (GPIO "); Serial.print(LORA_PWR_EN_PIN); Serial.println(")...");
  pinMode(LORA_PWR_EN_PIN, OUTPUT);
  digitalWrite(LORA_PWR_EN_PIN, HIGH);
  delay(100);
  Serial.println("Power Enable Done.");

  // Schritt 2: Pin Modes setzen
  Serial.println("Setting initial pin modes...");
  pinMode(LORA_NSS_PIN, OUTPUT); digitalWrite(LORA_NSS_PIN, HIGH);
  pinMode(LORA_RESET_PIN, OUTPUT); digitalWrite(LORA_RESET_PIN, HIGH);
  pinMode(LORA_BUSY_PIN, INPUT);
  pinMode(LORA_DIO1_PIN, INPUT);
  pinMode(LORA_MISO_PIN, INPUT_PULLUP); // Tested with and without PULLUP
  Serial.println("Pin modes set.");

  // Schritt 3: Manueller Reset
  Serial.println("Performing manual reset...");
  digitalWrite(LORA_RESET_PIN, LOW); delay(100);
  digitalWrite(LORA_RESET_PIN, HIGH); delay(500);
  Serial.println("Manual reset done.");

  // Schritt 4: SPI Init (Handled by RadioLib Constructor)
  Serial.println("SPI initialization handled by RadioLib constructor with SPISettings(8MHz).");
  delay(50);

  // Schritt 5: Radio Initialisierung (Tried with and without tcxoVoltage param here)
  Serial.print("Initializing SX1262 (Pinout 1), TCXO voltage "); Serial.print(tcxoVoltage); Serial.print("V assumed from build flags, using default regulator...");
  int state = radio.begin(868.1, 125.0, 7, 5, RADIOLIB_SX126X_SYNC_WORD_PUBLIC, 14, 8); // Tried with tcxoVoltage param too

  if (state == RADIOLIB_ERR_NONE) {
    Serial.println("\n********** SUCCESS! Chip found! **********");
    while(true) { delay(1000); }
  } else {
    Serial.print("FAILED! Chip not found or basic init failed, error code: "); Serial.println(state);
    Serial.println("Last attempt failed. Hardware check (B2B) or deeper Meshtastic code analysis needed.");
    while (true);
  }
}

void loop() { }

[HeadBoffin]

Was this recycled through some AI with the bold section on Could anyone familiar with the Meshtastic added using some passive-aggressive mode?

I doubt anyone has the (voluntary) time to figure how your question has changed, so best post the details that @jgromes suggested or tell us what's new.

Even @jgromes, the ultimate subject matter expert on RL, would have to trawl through the Meshtastic code for your hardware combo to look for differences in setup - is there something stopping you doing that?