HAL_Linux: added RCInput_115200

this is a RCInput module for multiple R/C uart protocols running at
115200 baud 8-bit. We can decode multiple protocols in parallel with
this module, relying on frame timing and CRCs to get the right
protocol

libraries/AP_HAL_Linux/RCInput.cpp

@@ -12,6 +12,8 @@
 
 #include <AP_HAL/AP_HAL.h>
 #include <AP_HAL/utility/dsm.h>
+#include <AP_HAL/utility/sumd.h>
+#include <AP_HAL/utility/st24.h>
 
 #include "RCInput.h"
 #include "sbus.h"
@@ -408,6 +410,61 @@ void RCInput::add_dsm_input(const uint8_t *bytes, size_t nbytes)
 }
 
 
+/*
+  add some bytes of input in SUMD serial stream format, coping with partial packets
+ */
+void RCInput::add_sumd_input(const uint8_t *bytes, size_t nbytes)
+{
+    uint16_t values[LINUX_RC_INPUT_NUM_CHANNELS];
+    uint8_t rssi;
+    uint8_t rx_count;
+    uint16_t channel_count;
+
+    while (nbytes > 0) {
+        if (sumd_decode(*bytes++, &rssi, &rx_count, &channel_count, values, LINUX_RC_INPUT_NUM_CHANNELS) == 0) {
+            if (channel_count > LINUX_RC_INPUT_NUM_CHANNELS) {
+                return;
+            }
+            for (uint8_t i=0; i<channel_count; i++) {
+                if (values[i] != 0) {
+                    _pwm_values[i] = values[i];
+                }
+            }
+            _num_channels = channel_count;
+            new_rc_input = true;
+        }
+        nbytes--;
+    }
+}
+
+/*
+  add some bytes of input in ST24 serial stream format, coping with partial packets
+ */
+void RCInput::add_st24_input(const uint8_t *bytes, size_t nbytes)
+{
+    uint16_t values[LINUX_RC_INPUT_NUM_CHANNELS];
+    uint8_t rssi;
+    uint8_t rx_count;
+    uint16_t channel_count;
+
+    while (nbytes > 0) {
+        if (st24_decode(*bytes++, &rssi, &rx_count, &channel_count, values, LINUX_RC_INPUT_NUM_CHANNELS) == 0) {
+            if (channel_count > LINUX_RC_INPUT_NUM_CHANNELS) {
+                return;
+            }
+            for (uint8_t i=0; i<channel_count; i++) {
+                if (values[i] != 0) {
+                    _pwm_values[i] = values[i];
+                }
+            }
+            _num_channels = channel_count;
+            new_rc_input = true;
+        }
+        nbytes--;
+    }
+}
+
+
 /*
   add some bytes of input in SBUS serial stream format, coping with partial packets
  */

libraries/AP_HAL_Linux/RCInput.h

@@ -34,7 +34,12 @@ public:
     // add some SBUS input bytes, for RCInput over a serial port
     void add_sbus_input(const uint8_t *bytes, size_t nbytes);
 
+    // add some SUMD input bytes, for RCInput over a serial port
+    void add_sumd_input(const uint8_t *bytes, size_t nbytes);
 
+    // add some st24 input bytes, for RCInput over a serial port
+    void add_st24_input(const uint8_t *bytes, size_t nbytes);
+    
 protected:
     void _process_rc_pulse(uint16_t width_s0, uint16_t width_s1);
     void _update_periods(uint16_t *periods, uint8_t len);

libraries/AP_HAL_Linux/RCInput_115200.cpp

@@ -0,0 +1,119 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*
+  this is a driver for R/C input protocols that use a 115200 baud
+  non-inverted 8-bit protocol. That includes:
+    - DSM
+    - SUMD
+    - ST24
+ */
+
+#include <AP_HAL/AP_HAL.h>
+
+#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_DISCO
+#include "RCInput_115200.h"
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/ioctl.h>
+#include <termios.h>
+#include <AP_HAL/utility/sumd.h>
+#include <AP_HAL/utility/st24.h>
+#include <AP_HAL/utility/dsm.h>
+
+extern const AP_HAL::HAL& hal;
+
+using namespace Linux;
+
+void RCInput_115200::init()
+{
+    fd = open(device_path, O_RDWR | O_NONBLOCK);
+    if (fd != -1) {
+        struct termios options;
+
+        tcgetattr(fd, &options);
+
+        cfsetispeed(&options, B115200);
+        cfsetospeed(&options, B115200);
+
+        options.c_cflag &= ~(PARENB|CSTOPB|CSIZE);
+        options.c_cflag |= CS8;
+
+        options.c_lflag &= ~(ICANON|ECHO|ECHOE|ISIG);
+        options.c_iflag &= ~(IXON|IXOFF|IXANY);
+        options.c_oflag &= ~OPOST;
+
+        if (tcsetattr(fd, TCSANOW, &options) != 0) {
+            AP_HAL::panic("RCInput_UART: error configuring device: %s",
+                          strerror(errno));
+        }
+
+        tcflush(fd, TCIOFLUSH);
+    }
+}
+
+void RCInput_115200::set_device_path(const char *path)
+{
+    device_path = path;
+}
+
+void RCInput_115200::_timer_tick(void)
+{
+    if (fd == -1) {
+        return;
+    }
+
+    // read up to 256 bytes at a time
+    uint8_t bytes[256];
+    int nread;
+    
+    fd_set fds;
+    struct timeval tv;
+    
+    FD_ZERO(&fds);
+    FD_SET(fd, &fds);
+
+    tv.tv_sec = 0;
+    tv.tv_usec = 0;
+
+    // check if any bytes are available
+    if (select(fd+1, &fds, NULL, NULL, &tv) != 1) {
+        return;
+    }
+
+    // cope with there being a large number of pending bytes at
+    // the start and discard them
+    do {
+        nread = ::read(fd, bytes, sizeof(bytes));
+    } while (nread == sizeof(bytes));
+
+    if (nread <= 0) {
+        return;
+    }
+
+    // process as DSM
+    add_dsm_input(bytes, nread);
+
+    // process as SUMD
+    add_sumd_input(bytes, nread);
+
+    // process as st24
+    add_st24_input(bytes, nread);
+}
+
+#endif // CONFIG_HAL_BOARD_SUBTYPE
+

libraries/AP_HAL_Linux/RCInput_115200.h

@@ -0,0 +1,41 @@
+/*
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <AP_HAL/AP_HAL.h>
+#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_DISCO
+
+#include "RCInput.h"
+
+namespace Linux {
+
+class RCInput_115200 : public RCInput
+{
+public:
+    RCInput_115200(const char *device) :
+       device_path(device) {}
+    void init() override;
+    void _timer_tick(void) override;
+    void set_device_path(const char *path);
+
+private:
+    const char *device_path;
+    int32_t fd = -1;
+};
+
+}
+
+#endif // CONFIG_HAL_BOARD_SUBTYPE