Add native SPI LoRa driver (SX1276/SX1262) as MEDIUM_LORA channel type

Introduces loraspi.c — a native Linux SPI/GPIO driver for SX1276 and
SX1262 LoRa chips — as a new channel medium alongside MEDIUM_RADIO,
MEDIUM_NETTNC, and MEDIUM_SERTNC.

New source files:
  src/loraspi.c  — driver: chip init, rx_thread (dlq_rec_frame injection),
                   tx_thread (AX.25 → TNC2 → LoRa preamble → SPI TX),
                   hardware profile table (loraspi_apply_profile)
  src/loraspi.h  — public API: loraspi_init, loraspi_send_packet,
                   loraspi_apply_profile

Modified source files:
  src/audio.h      — MEDIUM_LORA added to enum medium_e; ~18 lora_*[]
                     config fields added to struct audio_s
  src/config.c     — LCHANNEL, LORAHW, LORAFREQ, LORASF, LORABW, LORACR,
                     LORASW, LORATXPOWER directives parsed; all
                     chan_medium validity checks extended for MEDIUM_LORA
  src/direwolf.c   — loraspi_init() called at startup after sertnc_init()
  src/tq.c         — transmit queue routes MEDIUM_LORA packets to
                     loraspi_send_packet()
  src/beacon.c     — MEDIUM_LORA accepted for PBEACON/OBEACON channels
  src/digipeater.c — MEDIUM_LORA accepted as valid receive channel
  src/cdigipeater.c — MEDIUM_LORA accepted; bounds check widened from
                     MAX_RADIO_CHANS to MAX_TOTAL_CHANS for virtual channels
  src/CMakeLists.txt — loraspi.c added to direwolf source list

The driver is Linux-only; non-Linux platforms get empty stubs so the build
is unconditional.  A per-channel pthread_mutex_t serialises SPI access
between the rx and tx threads.  The chip is re-armed to continuous RX mode
after each transmission (SX1276 drops to STDBY on TX_DONE).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/CMakeLists.txt

@@ -88,6 +88,7 @@ list(APPEND direwolf_SOURCES
   tnc_common.c
   nettnc.c
   sertnc.c
+  loraspi.c
   serial_port.c
   pfilter.c
   ptt.c

src/audio.h

@@ -61,7 +61,8 @@ enum medium_e { MEDIUM_NONE = 0,	// Channel is not valid for use.
 		MEDIUM_RADIO,		// Internal modem for radio.
 		MEDIUM_IGATE,		// Access IGate as ordinary channel.
 		MEDIUM_NETTNC, 		// Remote network TNC.  (new in 1.8)
-		MEDIUM_SERTNC };	// Local serial TNC.  (new in 1.8)
+		MEDIUM_SERTNC,		// Local serial TNC.  (new in 1.8)
+		MEDIUM_LORA };		// Native SPI LoRa hat (SX1276/SX1262).
 
 
 typedef enum sanity_e { SANITY_APRS, SANITY_AX25, SANITY_NONE } sanity_t;
@@ -154,6 +155,7 @@ struct audio_s {
 					// MEDIUM_IGATE allows application access to IGate.
 					// MEDIUM_NETTNC for external TNC via TCP.
 					// MEDIUM_SERTNC for external TNC via serial port.
+					// MEDIUM_LORA   for native SPI LoRa hat (SX1276/SX1262).
 
 	int igate_vchannel;		/* Virtual channel mapped to APRS-IS. */
 					/* -1 for none. */
@@ -172,6 +174,27 @@ struct audio_s {
 
 	int sertnc_baud[MAX_TOTAL_CHANS];		// Serial TNC baud rate.
 
+	// Applies only to native SPI LoRa channels (MEDIUM_LORA).
+
+	int  lora_chip[MAX_TOTAL_CHANS];		// LORA_CHIP_SX1276 or LORA_CHIP_SX1262 (from loraspi.h)
+	float lora_freq_mhz[MAX_TOTAL_CHANS];		// Centre frequency, e.g. 915.0
+	int  lora_sf[MAX_TOTAL_CHANS];			// Spreading factor 6-12
+	float lora_bw_khz[MAX_TOTAL_CHANS];		// Bandwidth: 125, 250, 500 kHz
+	int  lora_cr[MAX_TOTAL_CHANS];			// Coding rate 5-8 (denominator of 4/x)
+	int  lora_sw[MAX_TOTAL_CHANS];			// Sync word (0x12 private, 0x34 LoRa-APRS)
+	int  lora_txpower[MAX_TOTAL_CHANS];		// TX power dBm
+	int  lora_pin_cs[MAX_TOTAL_CHANS];		// GPIO chip-select (BCM)
+	int  lora_pin_reset[MAX_TOTAL_CHANS];		// GPIO reset (-1 = not wired)
+	int  lora_pin_irq[MAX_TOTAL_CHANS];		// GPIO DIO0/IRQ (-1 = not wired)
+	int  lora_pin_busy[MAX_TOTAL_CHANS];		// GPIO BUSY for SX1262 (-1 = not used)
+	int  lora_pin_tx_en[MAX_TOTAL_CHANS];		// GPIO TX-enable for E22 (-1 = not used)
+	int  lora_pin_rx_en[MAX_TOTAL_CHANS];		// GPIO RX-enable for E22 (-1 = not used)
+	int  lora_pa_boost[MAX_TOTAL_CHANS];		// 1 = use PA_BOOST pin (SX1276)
+	int  lora_tcxo[MAX_TOTAL_CHANS];		// 1 = TCXO fitted (SX1262)
+	float lora_tcxo_voltage[MAX_TOTAL_CHANS];	// TCXO supply voltage, e.g. 1.8
+	int  lora_spi_bus[MAX_TOTAL_CHANS];		// spidev bus number (default 0)
+	int  lora_spi_dev[MAX_TOTAL_CHANS];		// spidev device number (default 0)
+	int  lora_spi_speed[MAX_TOTAL_CHANS];		// SPI clock Hz (default 8000000)
 
 
 	/* Properties for each radio channel, common to receive and transmit. */

src/beacon.c

@@ -166,7 +166,8 @@ void beacon_init (struct audio_s *pmodem, struct misc_config_s *pconfig, struct
 
 	  if (g_modem_config_p->chan_medium[chan] == MEDIUM_RADIO ||
 	      g_modem_config_p->chan_medium[chan] == MEDIUM_NETTNC ||
-	      g_modem_config_p->chan_medium[chan] == MEDIUM_SERTNC) {
+	      g_modem_config_p->chan_medium[chan] == MEDIUM_SERTNC ||
+	      g_modem_config_p->chan_medium[chan] == MEDIUM_LORA) {
 
 	    if (strlen(g_modem_config_p->mycall[chan]) > 0 &&
 			 strcasecmp(g_modem_config_p->mycall[chan], "N0CALL") != 0 &&

src/cdigipeater.c

@@ -132,10 +132,11 @@ void cdigipeater (int from_chan, packet_t pp)
 	// Connected mode is allowed only for channels with internal modem.
 	// It probably wouldn't matter for digipeating but let's keep that rule simple and consistent.
 
-	if ( from_chan < 0 || from_chan >= MAX_RADIO_CHANS ||
+	if ( from_chan < 0 || from_chan >= MAX_TOTAL_CHANS ||
 		(save_audio_config_p->chan_medium[from_chan] != MEDIUM_RADIO &&
 		save_audio_config_p->chan_medium[from_chan] != MEDIUM_NETTNC &&
-		save_audio_config_p->chan_medium[from_chan] != MEDIUM_SERTNC)  ) {
+		save_audio_config_p->chan_medium[from_chan] != MEDIUM_SERTNC &&
+		save_audio_config_p->chan_medium[from_chan] != MEDIUM_LORA)  ) {
 	  text_color_set(DW_COLOR_ERROR);
 	  dw_printf ("cdigipeater: Did not expect to receive on invalid channel %d.\n", from_chan);
 	  return;

src/config.c

@@ -63,6 +63,7 @@
 #include "xmit.h"
 #include "tt_text.h"
 #include "ax25_link.h"
+#include "loraspi.h"
 
 #if USE_CM108		// Current Linux or Windows only
 #include "cm108.h"
@@ -1444,6 +1445,181 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	    }
 	  }
 
+/*
+ * LCHANNEL  chan
+ *
+ *	Declare a virtual channel as a native SPI LoRa channel (SX1276/SX1262).
+ *	Sets the current channel context so subsequent MYCALL, LORAHW, LORAFREQ,
+ *	LORASF, LORABW, LORACR, LORASW, LORATXPOWER directives apply to it.
+ *
+ *	Example:
+ *		LCHANNEL 10
+ *		MYCALL   K6ATV-2
+ *		LORAHW   lorapi_rfm95w
+ *		LORAFREQ 915.0
+ *		LORASF   12
+ */
+	  else if (strcasecmp(t, "LCHANNEL") == 0) {
+	    t = split(NULL,0);
+	    if (t == NULL) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: Missing channel number for LCHANNEL command.\n", line);
+	      continue;
+	    }
+	    int lchan = atoi(t);
+	    if (lchan >= MAX_RADIO_CHANS && lchan < MAX_TOTAL_CHANS) {
+	      if (p_audio_config->chan_medium[lchan] == MEDIUM_NONE) {
+	        p_audio_config->chan_medium[lchan] = MEDIUM_LORA;
+	        /* Set defaults */
+	        p_audio_config->lora_freq_mhz[lchan]    = 915.0f;
+	        p_audio_config->lora_sf[lchan]           = 12;
+	        p_audio_config->lora_bw_khz[lchan]       = 125.0f;
+	        p_audio_config->lora_cr[lchan]           = 5;
+	        p_audio_config->lora_sw[lchan]           = 0x34;	/* LoRa-APRS sync word */
+	        p_audio_config->lora_txpower[lchan]      = 20;
+	        p_audio_config->lora_pin_cs[lchan]       = -1;
+	        p_audio_config->lora_pin_reset[lchan]    = -1;
+	        p_audio_config->lora_pin_irq[lchan]      = -1;
+	        p_audio_config->lora_pin_busy[lchan]     = -1;
+	        p_audio_config->lora_pin_tx_en[lchan]    = -1;
+	        p_audio_config->lora_pin_rx_en[lchan]    = -1;
+	        p_audio_config->lora_pa_boost[lchan]     = 0;
+	        p_audio_config->lora_tcxo[lchan]         = 0;
+	        p_audio_config->lora_tcxo_voltage[lchan] = 1.8f;
+	        p_audio_config->lora_spi_bus[lchan]      = 0;
+	        p_audio_config->lora_spi_dev[lchan]      = 0;
+	        p_audio_config->lora_spi_speed[lchan]    = 8000000;
+	        channel = lchan;	/* set context for subsequent LORAHW etc. */
+	      }
+	      else {
+	        text_color_set(DW_COLOR_ERROR);
+	        dw_printf ("Line %d: LCHANNEL can't use channel %d because it is already in use.\n", line, lchan);
+	      }
+	    }
+	    else {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LCHANNEL number must be in range %d to %d.\n", line, MAX_RADIO_CHANS, MAX_TOTAL_CHANS-1);
+	    }
+	  }
+
+/*
+ * LORAHW  profile-name
+ *
+ *	Load GPIO pin and chip settings from a built-in hardware profile.
+ *	Must follow an LCHANNEL directive.  Profile names match entries in
+ *	the s_profiles[] table in loraspi.c.
+ *	Example: LORAHW lorapi_rfm95w
+ */
+	  else if (strcasecmp(t, "LORAHW") == 0) {
+	    if (channel < MAX_RADIO_CHANS || p_audio_config->chan_medium[channel] != MEDIUM_LORA) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LORAHW must follow an LCHANNEL directive.\n", line);
+	      continue;
+	    }
+	    t = split(NULL,0);
+	    if (t == NULL) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: Missing hardware profile name for LORAHW.\n", line);
+	      continue;
+	    }
+	    if (loraspi_apply_profile(channel, t, p_audio_config) != 0) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: Unknown LoRa hardware profile '%s'.\n", line, t);
+	    }
+	  }
+
+/*
+ * LORAFREQ  frequency_mhz
+ *	Example: LORAFREQ 915.0
+ */
+	  else if (strcasecmp(t, "LORAFREQ") == 0) {
+	    if (channel < MAX_RADIO_CHANS || p_audio_config->chan_medium[channel] != MEDIUM_LORA) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LORAFREQ must follow an LCHANNEL directive.\n", line);
+	      continue;
+	    }
+	    t = split(NULL,0);
+	    if (t != NULL) p_audio_config->lora_freq_mhz[channel] = (float)atof(t);
+	  }
+
+/*
+ * LORASF  spreading_factor    (6-12)
+ *	Example: LORASF 12
+ */
+	  else if (strcasecmp(t, "LORASF") == 0) {
+	    if (channel < MAX_RADIO_CHANS || p_audio_config->chan_medium[channel] != MEDIUM_LORA) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LORASF must follow an LCHANNEL directive.\n", line);
+	      continue;
+	    }
+	    t = split(NULL,0);
+	    if (t != NULL) {
+	      int sf = atoi(t);
+	      if (sf >= 6 && sf <= 12) p_audio_config->lora_sf[channel] = sf;
+	      else { text_color_set(DW_COLOR_ERROR); dw_printf ("Line %d: LORASF must be 6-12.\n", line); }
+	    }
+	  }
+
+/*
+ * LORABW  bandwidth_khz    (125, 250, or 500)
+ *	Example: LORABW 125
+ */
+	  else if (strcasecmp(t, "LORABW") == 0) {
+	    if (channel < MAX_RADIO_CHANS || p_audio_config->chan_medium[channel] != MEDIUM_LORA) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LORABW must follow an LCHANNEL directive.\n", line);
+	      continue;
+	    }
+	    t = split(NULL,0);
+	    if (t != NULL) p_audio_config->lora_bw_khz[channel] = (float)atof(t);
+	  }
+
+/*
+ * LORACR  coding_rate    (5-8, meaning 4/5 to 4/8)
+ *	Example: LORACR 5
+ */
+	  else if (strcasecmp(t, "LORACR") == 0) {
+	    if (channel < MAX_RADIO_CHANS || p_audio_config->chan_medium[channel] != MEDIUM_LORA) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LORACR must follow an LCHANNEL directive.\n", line);
+	      continue;
+	    }
+	    t = split(NULL,0);
+	    if (t != NULL) {
+	      int cr = atoi(t);
+	      if (cr >= 5 && cr <= 8) p_audio_config->lora_cr[channel] = cr;
+	      else { text_color_set(DW_COLOR_ERROR); dw_printf ("Line %d: LORACR must be 5-8.\n", line); }
+	    }
+	  }
+
+/*
+ * LORASW  sync_word_hex    (0x12 for private, 0x34 for LoRa-APRS standard)
+ *	Example: LORASW 0x34
+ */
+	  else if (strcasecmp(t, "LORASW") == 0) {
+	    if (channel < MAX_RADIO_CHANS || p_audio_config->chan_medium[channel] != MEDIUM_LORA) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LORASW must follow an LCHANNEL directive.\n", line);
+	      continue;
+	    }
+	    t = split(NULL,0);
+	    if (t != NULL) p_audio_config->lora_sw[channel] = (int)strtol(t, NULL, 0);
+	  }
+
+/*
+ * LORATXPOWER  dbm
+ *	Example: LORATXPOWER 20
+ */
+	  else if (strcasecmp(t, "LORATXPOWER") == 0) {
+	    if (channel < MAX_RADIO_CHANS || p_audio_config->chan_medium[channel] != MEDIUM_LORA) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Line %d: LORATXPOWER must follow an LCHANNEL directive.\n", line);
+	      continue;
+	    }
+	    t = split(NULL,0);
+	    if (t != NULL) p_audio_config->lora_txpower[channel] = atoi(t);
+	  }
+
 /*
  * MYCALL station
  */
@@ -2813,7 +2989,8 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 
 	    if (p_audio_config->chan_medium[from_chan] != MEDIUM_RADIO &&
 	        p_audio_config->chan_medium[from_chan] != MEDIUM_NETTNC &&
-	        p_audio_config->chan_medium[from_chan] != MEDIUM_SERTNC) {
+	        p_audio_config->chan_medium[from_chan] != MEDIUM_SERTNC &&
+	        p_audio_config->chan_medium[from_chan] != MEDIUM_LORA) {
 	      text_color_set(DW_COLOR_ERROR);
 	      dw_printf ("Config file, line %d: FROM-channel %d is not valid.\n", 
 							line, from_chan);
@@ -2842,7 +3019,8 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 
 	    if (p_audio_config->chan_medium[to_chan] != MEDIUM_RADIO &&
 	        p_audio_config->chan_medium[to_chan] != MEDIUM_NETTNC &&
-	        p_audio_config->chan_medium[to_chan] != MEDIUM_SERTNC) {
+	        p_audio_config->chan_medium[to_chan] != MEDIUM_SERTNC &&
+	        p_audio_config->chan_medium[to_chan] != MEDIUM_LORA) {
 	      text_color_set(DW_COLOR_ERROR);
 	      dw_printf ("Config file, line %d: TO-channel %d is not valid.\n", 
 							line, to_chan);
@@ -3177,7 +3355,8 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 
 	      if (p_audio_config->chan_medium[from_chan] != MEDIUM_RADIO &&
 		  p_audio_config->chan_medium[from_chan] != MEDIUM_NETTNC &&
-		  p_audio_config->chan_medium[from_chan] != MEDIUM_SERTNC) {
+		  p_audio_config->chan_medium[from_chan] != MEDIUM_SERTNC &&
+		  p_audio_config->chan_medium[from_chan] != MEDIUM_LORA) {
 	        text_color_set(DW_COLOR_ERROR);
 	        dw_printf ("Config file, line %d: FROM-channel %d is not valid.\n", 
 							line, from_chan);
@@ -3216,7 +3395,8 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	      }
 	      if (p_audio_config->chan_medium[to_chan] != MEDIUM_RADIO &&
 		  p_audio_config->chan_medium[to_chan] != MEDIUM_NETTNC &&
-		  p_audio_config->chan_medium[to_chan] != MEDIUM_SERTNC) {
+		  p_audio_config->chan_medium[to_chan] != MEDIUM_SERTNC &&
+		  p_audio_config->chan_medium[to_chan] != MEDIUM_LORA) {
 	        text_color_set(DW_COLOR_ERROR);
 	        dw_printf ("Config file, line %d: TO-channel %d is not valid.\n", 
 							line, to_chan);
@@ -4497,7 +4677,8 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	        }
 	        else if (p_audio_config->chan_medium[x] != MEDIUM_RADIO &&
 			 p_audio_config->chan_medium[x] != MEDIUM_NETTNC &&
-			 p_audio_config->chan_medium[x] != MEDIUM_SERTNC) {
+			 p_audio_config->chan_medium[x] != MEDIUM_SERTNC &&
+			 p_audio_config->chan_medium[x] != MEDIUM_LORA) {
 	          text_color_set(DW_COLOR_ERROR);
 	          dw_printf ("Config file, line %d: TTOBJ transmit channel %d is not valid.\n", line, x);
 	          x = -1;
@@ -5940,7 +6121,8 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	  if (strlen(p_igate_config->t2_login) > 0 &&
 	      (p_audio_config->chan_medium[i] == MEDIUM_RADIO ||
 	        p_audio_config->chan_medium[i] == MEDIUM_NETTNC ||
-	        p_audio_config->chan_medium[i] == MEDIUM_SERTNC)) {
+	        p_audio_config->chan_medium[i] == MEDIUM_SERTNC ||
+	        p_audio_config->chan_medium[i] == MEDIUM_LORA)) {
 
 	    if (strcmp(p_audio_config->mycall[i], "NOCALL") == 0  || strcmp(p_audio_config->mycall[i], "N0CALL") == 0) {
 	      text_color_set(DW_COLOR_ERROR);
@@ -5968,7 +6150,8 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	  for (j=0; j<MAX_TOTAL_CHANS; j++) {
 	    if (p_audio_config->chan_medium[j] == MEDIUM_RADIO ||
 	        p_audio_config->chan_medium[j] == MEDIUM_NETTNC ||
-	        p_audio_config->chan_medium[j] == MEDIUM_SERTNC) {
+	        p_audio_config->chan_medium[j] == MEDIUM_SERTNC ||
+	        p_audio_config->chan_medium[j] == MEDIUM_LORA) {
 	      if (p_digi_config->filter_str[MAX_TOTAL_CHANS][j] == NULL) {
 	        p_digi_config->filter_str[MAX_TOTAL_CHANS][j] = strdup("i/180");
 	      }

src/digipeater.c

@@ -157,7 +157,8 @@ void digipeater (int from_chan, packet_t pp)
 	if ( from_chan < 0 || from_chan >= MAX_TOTAL_CHANS ||
 	     (save_audio_config_p->chan_medium[from_chan] != MEDIUM_RADIO &&
 	      save_audio_config_p->chan_medium[from_chan] != MEDIUM_NETTNC &&
-	      save_audio_config_p->chan_medium[from_chan] != MEDIUM_SERTNC)) {
+	      save_audio_config_p->chan_medium[from_chan] != MEDIUM_SERTNC &&
+	      save_audio_config_p->chan_medium[from_chan] != MEDIUM_LORA)) {
 	  text_color_set(DW_COLOR_ERROR);
 	  dw_printf ("APRS digipeater: Did not expect to receive on invalid channel %d.\n", from_chan);
 	}

src/direwolf.c

@@ -132,6 +132,7 @@
 #include "deviceid.h"
 #include "nettnc.h"
 #include "sertnc.h"
+#include "loraspi.h"
 
 
 //static int idx_decoded = 0;
@@ -1063,6 +1064,7 @@ int main (int argc, char *argv[])
  */
 	nettnc_init (&audio_config);
 	sertnc_init (&audio_config);
+	loraspi_init (&audio_config);
 
 /*
  * Initialize the touch tone decoder & APRStt gateway.