From c46ec5778d4d4d7be2b5041c6a83e321406f83c1 Mon Sep 17 00:00:00 2001
From: Adam Novak <interfect@gmail.com>
Date: Sun, 13 Feb 2022 18:40:30 -0500
Subject: [PATCH] Actually implement Linux SPI access

---
 LoRa.cpp | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 LoRa.h   | 16 ++++++++++------
 Makefile |  3 +++
 3 files changed, 59 insertions(+), 7 deletions(-)

diff --git a/LoRa.cpp b/LoRa.cpp
index 1ce035d..1b20596 100644
--- a/LoRa.cpp
+++ b/LoRa.cpp
@@ -11,6 +11,10 @@
   #include <unistd.h>
   // And we need to use the filesystem and IOCTLs instead of an SPI global
   #include <fcntl.h>
+  #include <sys/ioctl.h>
+  #include <linux/spi/spidev.h>
+  // And to have memset
+  #include <cstring>
   // And we need to be able to report errors
   #include <stdio.h>
   #include <errno.h>
@@ -683,6 +687,7 @@ uint8_t ISR_VECT LoRaClass::singleTransfer(uint8_t address, uint8_t value)
   uint8_t response;
   
 #if LIBRARY_TYPE == LIBRARY_ARDUINO
+  // Select chip, send address, and send/read data, the Arduino way
   digitalWrite(_ss, LOW);
 
   SPI.beginTransaction(_spiSettings);
@@ -692,7 +697,47 @@ uint8_t ISR_VECT LoRaClass::singleTransfer(uint8_t address, uint8_t value)
 
   digitalWrite(_ss, HIGH);
 #elif LIBRARY_TYPE == LIBRARY_C
-
+  // Select chip, send address, and send/read data, the Linux way
+  
+  // In Linux, chip select is automatically turned off outside of transactions.
+  
+  int status;
+  
+  // Configure SPI speed and mode to match settings
+  status = ioctl(_fd, SPI_IOC_WR_MODE, &_spiSettings.mode);
+  if (status < 0) {
+    perror("ioctl SPI_IOC_WR_MODE failed");
+    exit(1);
+  }
+  status = ioctl(_fd, SPI_IOC_WR_LSB_FIRST, &_spiSettings.bitness);
+  if (status < 0) {
+    perror("ioctl SPI_IOC_WR_LSB_FIRST failed");
+    exit(1);
+  }
+  status = ioctl(_fd, SPI_IOC_WR_MAX_SPEED_HZ, &_spiSettings.frequency);
+  if (status < 0) {
+    perror("ioctl SPI_IOC_WR_MAX_SPEED_HZ failed");
+    exit(1);
+  }
+  
+  // We have two transfers: one send-only to send the address, and one
+  // send/receive, to send the value and get the response. 
+  struct spi_ioc_transfer xfer[2];
+  memset(xfer, 0, sizeof xfer);
+  
+  xfer[0].tx_buf = (unsigned long) &address;
+  xfer[0].len = 1;
+  
+  xfer[1].tx_buf = (unsigned long) &value;
+  xfer[1].rx_buf = (unsigned long) &response;
+  xfer[1].len = 1;
+  
+  // Do the transaction
+  status = ioctl(_fd, SPI_IOC_MESSAGE(2), xfer);
+  if (status < 0) {
+    perror("ioctl SPI_IOC_MESSAGE failed");
+    exit(1);
+  }
 #else
     #error "SPI transfer not implemented for library type"
 #endif
diff --git a/LoRa.h b/LoRa.h
index 5793337..e57543a 100644
--- a/LoRa.h
+++ b/LoRa.h
@@ -22,16 +22,20 @@
     
     typedef unsigned char byte;
     
-    // Arduino SPI is not available.
+    // Arduino SPI is not available, so make a Linux-ish version of SPISettings
     #define MSBFIRST 0
-    #define SPI_MODE0 0
+    #define LSBFIRST 1
+    #define SPI_MODE0 SPI_MODE_0
+    #define SPI_MODE1 SPI_MODE_1
+    #define SPI_MODE2 SPI_MODE_2
+    #define SPI_MODE3 SPI_MODE_3
     class SPISettings {
     public:
-      inline SPISettings(int frequency, int bitness, int mode) : frequency(frequency), bitness(bitness), mode(mode) {};
+      inline SPISettings(uint32_t frequency, byte bitness, byte mode) : frequency(frequency), bitness(bitness), mode(mode) {};
       SPISettings& operator=(const SPISettings& other) = default;
-      int frequency;
-      int bitness;
-      int mode;
+      uint32_t frequency;
+      byte bitness;
+      byte mode;
     };
     
 #endif
diff --git a/Makefile b/Makefile
index fda102b..b66d955 100644
--- a/Makefile
+++ b/Makefile
@@ -151,3 +151,6 @@ obj/MD5.o: MD5.cpp MD5.h Config.h ROM.h Platform.h prep-linux
 obj/LoRa.o: LoRa.cpp LoRa.h Platform.h prep-linux
 	$(CC) -c -o $@ $<
 	
+obj/RNode_firmware.o: RNode_firmware.ino Utilities.h Config.h LoRa.h ROM.h Framing.h MD5.h Platform.h prep-linux
+	$(CC) -c -o $@ $<
+