ArduPilot开源代码之AP_OSD_MSP_DisplayPort
1. 源由
前面讨论了
本章将针对具体的AP_OSD_MSP_DisplayPort类进行研讨。
2. 结构设计
2.1 成员变量
新增：
- AP_MSP_Telem_Backend* _displayport;
- bool _blink_on;
2.2 OSD 符号
显然，这里和 AP_OSD_Backend 不一致。
这也比较符合实际情况，不同的实现由于历史原因，或多或少都是不相同的，尤其开源的规划更加分散。
// MSP DisplayPort symbols
static const uint8_t SYM_M = 0x0C;
static const uint8_t SYM_KM = 0x7D;
static const uint8_t SYM_FT = 0x0F;
static const uint8_t SYM_MI = 0x7E;
static const uint8_t SYM_ALT_M = 0x0C;
static const uint8_t SYM_ALT_FT = 0x0F;
static const uint8_t SYM_BATT_FULL = 0x90;
static const uint8_t SYM_RSSI = 0x01;
static const uint8_t SYM_VOLT = 0x06;
static const uint8_t SYM_AMP = 0x9A;
static const uint8_t SYM_MAH = 0x07;
static const uint8_t SYM_MS = 0x9F;
static const uint8_t SYM_FS = 0x99;
static const uint8_t SYM_KMH = 0x9E;
static const uint8_t SYM_MPH = 0x9D;
static const uint8_t SYM_DEGR = 0x08;
static const uint8_t SYM_PCNT = 0x25;
static const uint8_t SYM_RPM = 0x12;
static const uint8_t SYM_ASPD = 0x41;
static const uint8_t SYM_GSPD = 0x47;
static const uint8_t SYM_WSPD = 0x57;
static const uint8_t SYM_VSPD = 0x5E;
static const uint8_t SYM_WPNO = 0x23;
static const uint8_t SYM_WPDIR = 0xE6;
static const uint8_t SYM_WPDST = 0xE7;
static const uint8_t SYM_FTMIN = 0xE8;
static const uint8_t SYM_FTSEC = 0x99;
static const uint8_t SYM_SAT_L = 0x1E;
static const uint8_t SYM_SAT_R = 0x1F;
static const uint8_t SYM_HDOP_L = 0x48;
static const uint8_t SYM_HDOP_R = 0x44;
static const uint8_t SYM_HOME = 0x11;
static const uint8_t SYM_WIND = 0x57;
static const uint8_t SYM_ARROW_START = 0x60;
static const uint8_t SYM_ARROW_COUNT = 16;
static const uint8_t SYM_AH_H_START = 0x80;
static const uint8_t SYM_AH_H_COUNT = 9;
static const uint8_t SYM_AH_V_START = 0x82;
static const uint8_t SYM_AH_V_COUNT = 6;
static const uint8_t SYM_AH_CENTER_LINE_LEFT = 0x84;
static const uint8_t SYM_AH_CENTER_LINE_RIGHT = 0x84;
static const uint8_t SYM_AH_CENTER = 0x2B;
static const uint8_t SYM_HEADING_N = 0x18;
static const uint8_t SYM_HEADING_S = 0x19;
static const uint8_t SYM_HEADING_E = 0x1A;
static const uint8_t SYM_HEADING_W = 0x1B;
static const uint8_t SYM_HEADING_DIVIDED_LINE = 0x1C;
static const uint8_t SYM_HEADING_LINE = 0x1D;
static const uint8_t SYM_UP_UP = 0x68;
static const uint8_t SYM_UP = 0x68;
static const uint8_t SYM_DOWN = 0x60;
static const uint8_t SYM_DOWN_DOWN = 0x60;
static const uint8_t SYM_DEGREES_C = 0x0E;
static const uint8_t SYM_DEGREES_F = 0x0D;
static const uint8_t SYM_GPS_LAT = 0x89;
static const uint8_t SYM_GPS_LONG = 0x98;
static const uint8_t SYM_ARMED = 0x00;
static const uint8_t SYM_DISARMED = 0x2A;
static const uint8_t SYM_ROLL0 = 0x2D;
static const uint8_t SYM_ROLLR = 0x64;
static const uint8_t SYM_ROLLL = 0x6C;
static const uint8_t SYM_PTCH0 = 0x7C;
static const uint8_t SYM_PTCHUP = 0x68;
static const uint8_t SYM_PTCHDWN = 0x60;
static const uint8_t SYM_XERR = 0x21;
static const uint8_t SYM_KN = 0xF0;
static const uint8_t SYM_NM = 0xF1;
static const uint8_t SYM_DIST = 0x04;
static const uint8_t SYM_FLY = 0x9C;
static const uint8_t SYM_EFF = 0xF2;
static const uint8_t SYM_AH = 0xF3;
static const uint8_t SYM_MW = 0xF4;
static const uint8_t SYM_CLK = 0x08;
static const uint8_t SYM_KILO = 0x4B;
static const uint8_t SYM_TERALT = 0x7F;
static const uint8_t SYM_FENCE_ENABLED = 0xF5;
static const uint8_t SYM_FENCE_DISABLED = 0xF6;
static const uint8_t SYM_RNGFD = 0x7F;
static const uint8_t SYM_LQ = 0xF8;
static const uint8_t SYM_SIDEBAR_L_ARROW = 0x02;
static const uint8_t SYM_SIDEBAR_R_ARROW = 0x03;
static const uint8_t SYM_SIDEBAR_A = 0x13;
static const uint8_t SYM_SIDEBAR_B = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_C = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_D = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_E = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_F = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_G = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_H = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_I = SYM_SIDEBAR_A;
static const uint8_t SYM_SIDEBAR_J = SYM_SIDEBAR_A;
static constexpr uint8_t symbols[AP_OSD_NUM_SYMBOLS] {
SYM_M,
SYM_KM,
SYM_FT,
SYM_MI,
SYM_ALT_M,
SYM_ALT_FT,
SYM_BATT_FULL,
SYM_RSSI,
SYM_VOLT,
SYM_AMP,
SYM_MAH,
SYM_MS,
SYM_FS,
SYM_KMH,
SYM_MPH,
SYM_DEGR,
SYM_PCNT,
SYM_RPM,
SYM_ASPD,
SYM_GSPD,
SYM_WSPD,
SYM_VSPD,
SYM_WPNO,
SYM_WPDIR,
SYM_WPDST,
SYM_FTMIN,
SYM_FTSEC,
SYM_SAT_L,
SYM_SAT_R,
SYM_HDOP_L,
SYM_HDOP_R,
SYM_HOME,
SYM_WIND,
SYM_ARROW_START,
SYM_ARROW_COUNT,
SYM_AH_H_START,
SYM_AH_H_COUNT,
SYM_AH_V_START,
SYM_AH_V_COUNT,
SYM_AH_CENTER_LINE_LEFT,
SYM_AH_CENTER_LINE_RIGHT,
SYM_AH_CENTER,
SYM_HEADING_N,
SYM_HEADING_S,
SYM_HEADING_E,
SYM_HEADING_W,
SYM_HEADING_DIVIDED_LINE,
SYM_HEADING_LINE,
SYM_UP_UP,
SYM_UP,
SYM_DOWN,
SYM_DOWN_DOWN,
SYM_DEGREES_C,
SYM_DEGREES_F,
SYM_GPS_LAT,
SYM_GPS_LONG,
SYM_ARMED,
SYM_DISARMED,
SYM_ROLL0,
SYM_ROLLR,
SYM_ROLLL,
SYM_PTCH0,
SYM_PTCHUP,
SYM_PTCHDWN,
SYM_XERR,
SYM_KN,
SYM_NM,
SYM_DIST,
SYM_FLY,
SYM_EFF,
SYM_AH,
SYM_MW,
SYM_CLK,
SYM_KILO,
SYM_TERALT,
SYM_FENCE_ENABLED,
SYM_FENCE_DISABLED,
SYM_RNGFD,
SYM_LQ,
SYM_SIDEBAR_L_ARROW,
SYM_SIDEBAR_R_ARROW,
SYM_SIDEBAR_A,
SYM_SIDEBAR_B,
SYM_SIDEBAR_C,
SYM_SIDEBAR_D,
SYM_SIDEBAR_E,
SYM_SIDEBAR_F,
SYM_SIDEBAR_G,
SYM_SIDEBAR_H,
SYM_SIDEBAR_I,
SYM_SIDEBAR_J,
};
3. 接口设计
3.1 一次性接口
3.1.1 init
查询配置为SerialProtocol_MSP_DisplayPort的UART端口，进行相关_displayport端口及配置初始化。
// initialise backend
bool AP_OSD_MSP_DisplayPort::init(void)
{
// check if we have a DisplayPort backend to use
const AP_MSP *msp = AP::msp();
if (msp == nullptr) {
GCS_SEND_TEXT(MAV_SEVERITY_WARNING,"MSP backend not available");
return false;
}
_displayport = msp->find_protocol(AP_SerialManager::SerialProtocol_MSP_DisplayPort);
if (_displayport == nullptr) {
GCS_SEND_TEXT(MAV_SEVERITY_WARNING,"MSP DisplayPort uart not available");
return false;
}
// re-init port here for use in this thread
_displayport->init_uart();
return true;
}
3.1.2 osd_thread_run_once
前面3.1.1函数在这里进行一次性的接口初始化
// called by the OSD thread once
void AP_OSD_MSP_DisplayPort::osd_thread_run_once()
{
if (_displayport != nullptr) {
_displayport->init_uart();
}
}
3.1.3 init_symbol_set
若选择配置了DISPLAYPORT_BTFL_SYMBOLS，则用继承类的符号表；否则，用Ardupilot原生(AP_OSD_Backend)的符号表。
void AP_OSD_MSP_DisplayPort::init_symbol_set(uint8_t *lookup_table, const uint8_t size)
{
const AP_MSP *msp = AP::msp();
// do we use backend specific symbols table?
if (msp && msp->is_option_enabled(AP_MSP::Option::DISPLAYPORT_BTFL_SYMBOLS)) {
memcpy(lookup_table, symbols, size);
} else {
memcpy(lookup_table, AP_OSD_Backend::symbols, size);
}
}
3.1.4 probe
最初的初始化，直接在AP_OSD::init_backend中进行，详见：ArduPilot开源代码之AP_OSD
AP_OSD_Backend *AP_OSD_MSP_DisplayPort::probe(AP_OSD &osd)
{
AP_OSD_MSP_DisplayPort *backend = NEW_NOTHROW AP_OSD_MSP_DisplayPort(osd);
if (!backend) {
return nullptr;
}
if (!backend->init()) {
delete backend;
return nullptr;
}
return backend;
}
3.2 基本操作
3.2.1 write
直接调用了AP_MSP_Telem_Backend的写字符串函数处理。
void AP_OSD_MSP_DisplayPort::write(uint8_t x, uint8_t y, const char* text)
{
_displayport->msp_displayport_write_string(x, y, 0, text);
}
3.2.2 flush
直接调用了AP_MSP_Telem_Backend的API函数处理。
void AP_OSD_MSP_DisplayPort::flush(void)
{
// grab the screen and force a redraw
_displayport->msp_displayport_grab();
_displayport->msp_displayport_draw_screen();
// ok done processing displayport data
// let's process incoming MSP frames (and reply if needed)
_displayport->process_incoming_data();
}
3.2.3 clear
直接调用了AP_MSP_Telem_Backend的API函数处理，并且_blink_on做了一个定期翻转。
void AP_OSD_MSP_DisplayPort::clear(void)
{
// check if we need to enable some options
// but only for actual OSD screens
if (_osd.get_current_screen() < AP_OSD_NUM_DISPLAY_SCREENS) {
const uint8_t txt_resolution = _osd.screen[_osd.get_current_screen()].get_txt_resolution();
const uint8_t font_index = _osd.screen[_osd.get_current_screen()].get_font_index();
_displayport->msp_displayport_set_options(font_index, txt_resolution);
}
// clear remote MSP screen
_displayport->msp_displayport_clear_screen();
// toggle flashing @1Hz
const uint32_t now = AP_HAL::millis();
if ((uint32_t(now * 0.004) & 0x01) != _blink_on) {
_blink_on = !_blink_on;
blink_phase = (blink_phase+1)%4;
}
}
按照以下方式修改，可能会更加清晰：
- 每秒闪烁一次，即每 500ms 切换一次状态
- 由于 now 是毫秒单位，now * 0.004 约等于每 250ms 变化一次整数
- & 0x01 会让这个值每500ms翻转一次，实现1Hz的闪烁效果
now (ms) | now * 0.004 | 整数值 | & 0x01 | _blink_on |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 250 | 1 | 1 | 1 | 1 (翻转) |
| 500 | 2 | 2 | 0 | 0 (翻转) |
| 750 | 3 | 3 | 1 | 1 (翻转) |
| 1000 | 4 | 4 | 0 | 0 (翻转) |
const uint32_t now = AP_HAL::millis();
if ((now / 500) % 2 != _blink_on) {
_blink_on = !_blink_on;
blink_phase = (blink_phase + 1) % 4;
}
3.3 功能函数
3.3.1 is_compatible_with_backend_type
- 不兼容：AP_OSD_MSP/AP_OSD_MSP_DISPLAYPORT
- 兼容：AP_OSD_MAX7456/AP_OSD_SITL
bool is_compatible_with_backend_type(AP_OSD::osd_types type) const override {
switch(type) {
case AP_OSD::osd_types::OSD_MSP:
case AP_OSD::osd_types::OSD_MSP_DISPLAYPORT:
return false;
case AP_OSD::osd_types::OSD_NONE:
case AP_OSD::osd_types::OSD_TXONLY:
case AP_OSD::osd_types::OSD_MAX7456:
case AP_OSD::osd_types::OSD_SITL:
return true;
}
return false;
}
3.3.2 get_backend_type
AP_OSD::osd_types get_backend_type() const override {
return AP_OSD::osd_types::OSD_MSP_DISPLAYPORT;
}
3.3.3 get_aspect_ratio_correction
不懂，什么原因要设置这个比率，请知道的朋友，评论告知，谢谢！ 请参考：ArduPilot开源代码之AP_OSD_MAX7456 对应章节解释。
// return a correction factor used to display angles correctly
float AP_OSD_MSP_DisplayPort::get_aspect_ratio_correction() const
{
return 12.0/18.0;
}
4. 总结
AP_OSD_MSP_DisplayPort类有点类似设备对象(DO)，然后协议层面是靠AP_MSP_Telem_Backend进行，应用层在AP_OSD处理。
5. 参考资料
【1】ArduPilot开源飞控系统之简单介绍
【2】ArduPilot之开源代码Task介绍
【3】ArduPilot飞控启动&运行过程简介
【4】ArduPilot之开源代码Library&Sketches设计
【5】ArduPilot之开源代码Sensor Drivers设计
【6】ArduPilot开源代码之AP_OSD_Backend
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