56 lines
1.7 KiB
Markdown
56 lines
1.7 KiB
Markdown
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# Sonar
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A sonar sensor can be used to measure altitude for use with BARO and SONAR altitude
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hold modes.
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The sonar sensor is used instead of the pressure sensor (barometer) at low altitudes (less than about 3.5 meters above the ground).
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The sonar sensor is only used when the aircraft inclination angle (attitude) is small (less than 22.5 degrees).
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## Hardware
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Currently the main supported sensor is the HCSR04 sensor.
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The Parallax 28015 single-wire sonar can also be used by connecting 1k resistors to the Trigger and Echo pins, and the other end of the resistors shorted together and to the Sonar module.
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```
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1k
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TRIGGER--/\/\--\
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\_______ 28015 SONAR
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1k /
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ECHO-----/\/\--/
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```
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## Connections
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### Naze/Flip32+
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| Mode | Trigger | Echo | Inline 1k resistors |
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| ------------------------------- | ------------- | ------------- | ------------------- |
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| Parallel PWM/ADC current sensor | PB8 / Motor 5 | PB9 / Motor 6 | NO (5v tolerant) |
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| PPM/Serial RX | PB0 / RC7 | PB1 / RC8 | YES (3.3v input) |
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#### Constraints
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Current meter cannot be used in conjunction with Parallel PWM and Sonar.
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### CC3D
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| Trigger | Echo | Inline 1k resistors |
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| ------------- | ------------- | ------------------- |
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| PB5 / RC4 | PB0 / RC5 | YES (3.3v input) |
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#### Constraints
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Sonar cannot be used in conjuction with SoftSerial or Parallel PWM.
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### SPRacingF3
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| Trigger | Echo | Inline 1k resistors |
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| ------------- | ------------- | ------------------- |
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| PB0 / RC7 | PB1 / RC8 | YES (3.3v input) |
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#### Constraints
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Sonar cannot be used in conjuction with SoftSerial2 or Parallel PWM.
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