From b93dee7fe6e4a96ba8be38af97a4a4d764551b43 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Mon, 5 Nov 2018 13:02:22 +1100
Subject: [PATCH] AP_RCProtocol: switched SRXL to SoftSerial decoder

---
 .../AP_RCProtocol/AP_RCProtocol_SRXL.cpp      | 65 ++-----------------
 libraries/AP_RCProtocol/AP_RCProtocol_SRXL.h  |  7 +-
 2 files changed, 7 insertions(+), 65 deletions(-)

diff --git a/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.cpp b/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.cpp
index e3b366993e..1d6260d177 100644
--- a/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.cpp
+++ b/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.cpp
@@ -49,69 +49,12 @@ uint16_t AP_RCProtocol_SRXL::srxl_crc16(uint16_t crc, uint8_t new_byte)
 
 void AP_RCProtocol_SRXL::process_pulse(uint32_t width_s0, uint32_t width_s1)
 {
-    // convert to bit widths, allowing for up to about 4usec error, assuming 115200 bps
-    uint16_t bits_s0 = ((width_s0+4)*(uint32_t)115200) / 1000000;
-    uint16_t bits_s1 = ((width_s1+4)*(uint32_t)115200) / 1000000;
-    uint8_t bit_ofs, byte_ofs;
-    uint16_t nbits;
-
+    uint8_t b;
+    if (ss.process_pulse(width_s0, width_s1, b)) {
+        _process_byte(clock_us, b, 115200);
+    }
     // keep a clock based on the pulses
     clock_us += (width_s0 + width_s1);
-
-    if (bits_s0 == 0 || bits_s1 == 0) {
-        // invalid data
-        goto reset;
-    }
-
-    byte_ofs = srxl_state.bit_ofs/10;
-    bit_ofs = srxl_state.bit_ofs%10;
-    if (byte_ofs >= SRXL_FRAMELEN_MAX) {
-        goto reset;
-    }
-    // pull in the high bits
-    nbits = bits_s0;
-    if (nbits+bit_ofs > 10) {
-        nbits = 10 - bit_ofs;
-    }
-    srxl_state.bytes[byte_ofs] |= ((1U<<nbits)-1) << bit_ofs;
-    srxl_state.bit_ofs += nbits;
-    bit_ofs += nbits;
-    if (bits_s0 - nbits > 10) {
-        // we have a full frame
-        uint8_t byte;
-        uint8_t i;
-        for (i=0; i <= byte_ofs; i++) {
-            // get raw data
-            uint16_t v = srxl_state.bytes[i];
-
-            // check start bit
-            if ((v & 1) != 0) {
-                break;
-            }
-            // check stop bits
-            if ((v & 0x200) != 0x200) {
-                break;
-            }
-            byte = ((v>>1) & 0xFF);
-            _process_byte(clock_us, byte, 115200);
-        }
-        memset(&srxl_state, 0, sizeof(srxl_state));
-    }
-
-    byte_ofs = srxl_state.bit_ofs/10;
-    bit_ofs = srxl_state.bit_ofs%10;
-
-    if (bits_s1+bit_ofs > 10) {
-        // invalid data
-        goto reset;
-    }
-
-    // pull in the low bits
-    srxl_state.bit_ofs += bits_s1;
-
-    return;
-reset:
-    memset(&srxl_state, 0, sizeof(srxl_state));
 }
 
 
diff --git a/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.h b/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.h
index f48c0ba076..fb4119f604 100644
--- a/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.h
+++ b/libraries/AP_RCProtocol/AP_RCProtocol_SRXL.h
@@ -18,6 +18,7 @@
 #pragma once
 
 #include "AP_RCProtocol.h"
+#include "SoftSerial.h"
 
 #define SRXL_MIN_FRAMESPACE_US 8000U    /* Minumum space between srxl frames in us (applies to all variants)  */
 #define SRXL_MAX_CHANNELS 20U           /* Maximum number of channels from srxl datastream  */
@@ -62,8 +63,6 @@ private:
     uint16_t crc_fmu = 0U;                       /* CRC calculated over payload from srxl datastream on this machine */
     uint16_t crc_receiver = 0U;                  /* CRC extracted from srxl datastream  */
     uint32_t clock_us;                           /* clock calculated from pulse lengths */
-    struct {
-        uint16_t bytes[SRXL_FRAMELEN_MAX];
-        uint16_t bit_ofs;
-    } srxl_state;
+
+    SoftSerial ss{115200, SoftSerial::SERIAL_CONFIG_8N1};
 };