faster UART speed, improve readme, cleanup

Author: bri3d

README.md

@@ -2,9 +2,11 @@
 
 This takes Betaflight MSP DisplayPort (so-called "canvas" although this is a misnomer as there is another Betaflight "canvas" mode for Pixel OSDs) messages through UDP and, using a font provided at `font.bin`, renders them to a framebuffer.
 
+A custom `font.bin` may be placed on the root of the SD card, at which point it will override the font in /blackbox. 
+
 SFML and DJI viewports available, as well as a mux which creates a pty and provides filtered MSP access, and reroutes DisplayPort messages to UDP.
 
-To build for DJI, install the Android NDK and add it to your path, then use make -f Makefile.dji .
+To build for DJI, install the Android NDK and add the NDK toolchain to your PATH, then use make -f Makefile.dji . Set DJI_LIB_PATH to a path to the content of `/system/lib` pulled from your DJI hardware or a firmware dump, so that the linker can find `libduml_hal.so`. On Windows, note that `make` and the actual `armv7a-linux-*` compiler binaries may be installed in different directories.
 
 To build for UNIXes, install CSFML and make -f Makefile.unix .
 
@@ -16,6 +18,13 @@ Provided targets and tools are:
 
 # Installation
 
+On your flight controller:
+
+* Ensure that the correct UART is set to use MSP.
+* Enable MSP DisplayPort. On Betaflight, this is done using the following commands:
+* `set osd_displayport_device = MSP`
+* `set displayport_msp_serial = <ConfiguratorUART - 1>` - for example, if the Configurator says UART2, the value here is `1`.
+
 On Air Unit / Air Unit Lite (Vista):
 ```
 adb push msp_displayport_mux /blackbox
@@ -25,6 +34,8 @@ nohup /blackbox/msp_displayport_mux 192.168.41.2 /dev/ttyS1_moved /dev/ttyS1
 ```
 This tells the displayport mux to send data from /dev/ttyS1_moved to 192.168.41.2 (goggles) and to create a fake serial port at /dev/ttyS1 with the displayport messages filtered out.
 
+Optionally, you can add `-f`, like `nohup /blackbox/msp_displayport_mux -f 192.168.41.2 /dev/ttyS1_moved /dev/ttyS1` to put the serial port in a faster 230400 baud mode, and set the MSP serial port in your flight controller to 230400 to try to improve the framerate.
+
 Now you can try `setprop dji.hdvt_uav_service 1` - depending on your FC it may or may not be able to handle the volume of MSP messages as well as DisplayPort at the same time.
 
 On goggles:

dji_services.c

@@ -3,31 +3,28 @@
 #include <sys/system_properties.h>
 #endif
 
+#define V2_SERVICE_NAME "dji.glasses_wm150_service"
+#define V1_SERVICE_NAME "dji.glasses_service"
+#define DEVICE_PROPERTY_NAME "ro.product.device"
+#define V2_GOGGLES_DEVICE "pigeon_wm170_gls"
+
 void dji_stop_goggles(int is_v2) {
 #ifdef __ANDROID_API__
-    if(is_v2) {
-        __system_property_set("dji.glasses_wm150_service", "0");
-    } else {
-        __system_property_set("dji.glasses_service", "0");
-    }
+    __system_property_set(is_v2 ? V2_SERVICE_NAME : V1_SERVICE_NAME, "0");
 #endif
 }
 
 void dji_start_goggles(int is_v2) {
 #ifdef __ANDROID_API__
-    if(is_v2) {
-        __system_property_set("dji.glasses_wm150_service", "1");
-    } else {
-        __system_property_set("dji.glasses_service", "1");
-    }
+    __system_property_set(is_v2 ? V2_SERVICE_NAME : V1_SERVICE_NAME, "1");
 #endif
 }
 
 int dji_goggles_are_v2() {
 #ifdef __ANDROID_API__
     char goggles_version_response[255];
-    int len = __system_property_get("ro.product.device", &goggles_version_response);
-    return(strcmp(goggles_version_response, "pigeon_wm170_gls") == 0);
+    int len = __system_property_get(DEVICE_PROPERTY_NAME, &goggles_version_response);
+    return(strcmp(goggles_version_response, V2_GOGGLES_DEVICE) == 0);
 #else
     return 0;
 #endif

msp_displayport_mux.c

@@ -53,28 +53,43 @@ static void msp_callback(msp_msg_t *msp_message)
 }
 
 int main(int argc, char *argv[]) {
-    if(argc < 3) {
-        printf("usage: msp_displayport_mux ipaddr serial_port [pty_target]");
+    int opt;
+    uint8_t fast_serial = 0;
+    while((opt = getopt(argc, argv, "f")) != -1){
+        switch(opt){
+        case 'f':
+            fast_serial = 1;
+            printf("Configuring serial to 230400 baud\n");
+            break;  
+        case '?':
+            printf("unknown option: %c\n", optopt);
+            break;
+        }
+    }
+  
+    if((argc - optind) < 2) {
+        printf("usage: msp_displayport_mux [-f] ipaddr serial_port [pty_target]");
         return 0;
     }
-    char *ip_address = argv[1];
-    char *serial_port = argv[2];
+
+    char *ip_address = argv[optind];
+    char *serial_port = argv[optind + 1];
     signal(SIGINT, sig_handler);
     struct pollfd poll_fds[2];
     const char *pty_name_ptr;
     msp_state_t *msp_state = calloc(1, sizeof(msp_state_t));
     msp_state->cb = &msp_callback;
-    serial_fd = open_serial_port(serial_port);
+    serial_fd = open_serial_port(serial_port, fast_serial ? B230400 : B115200);
     if (serial_fd <= 0) {
         printf("Failed to open serial port!\n");
         return 1;
     }
     pty_fd = open_pty(&pty_name_ptr);
     printf("Allocated PTY %s\n", pty_name_ptr);
-    if (argc > 3) {
-        unlink(argv[3]);
-        symlink(pty_name_ptr, argv[3]);   
-        printf("Relinked %s to %s\n", argv[3], pty_name_ptr); 
+    if ((argc - optind) > 2) {
+        unlink(argv[optind + 2]);
+        symlink(pty_name_ptr, argv[optind + 2]);   
+        printf("Relinked %s to %s\n", argv[optind + 2], pty_name_ptr); 
     }
     socket_fd = connect_to_server(ip_address, PORT);
     uint8_t serial_data[256];
@@ -99,7 +114,6 @@ int main(int argc, char *argv[]) {
         if(0 < (serial_data_size = read(pty_fd, serial_data, sizeof(serial_data)))) {
            write(serial_fd, &serial_data, serial_data_size);
         }
-
     }
     close(serial_fd);
     close(pty_fd);

serial.c

@@ -12,7 +12,7 @@
 #endif
 #include "serial.h"
 
-int open_serial_port(const char *device)
+int open_serial_port(const char *device, speed_t baudrate)
 {
     struct termios tio;
     int tty_fd;
@@ -26,8 +26,8 @@ int open_serial_port(const char *device)
     tio.c_cc[VTIME] = 0;
 
     tty_fd = open(device, O_RDWR | O_NONBLOCK);
-    cfsetospeed(&tio, B115200);
-    cfsetispeed(&tio, B115200);
+    cfsetospeed(&tio, baudrate);
+    cfsetispeed(&tio, baudrate);
     tcsetattr(tty_fd, TCSANOW, &tio);
     return tty_fd;
 }

serial.h

@@ -1,4 +1,6 @@
-int open_serial_port(const char *device);
+#include <termios.h>
+
+int open_serial_port(const char *device, speed_t baudrate);
 int open_pty(const char **pty_name);
 #ifdef __ANDROID__
 int