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0.3.0 SRF05
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Rob Tillaart
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@ -6,6 +6,16 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
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and this project adheres to [Semantic Versioning](http://semver.org/).
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## [0.3.0] - 2024-02-08
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- add support for single pin operation (echo == trigger) Kudos to RobertPHeller!
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- add **float getYards()** wrapper.
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- add **void setSampleInterval(uint16_t microSeconds = 1000)** (for average & median)
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- add **uint16_t getSampleInterval()**
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- reduced pulseIn timeout to 200000 (30+ meter)
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- minor edits.
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----
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## [0.2.0] - 2024-01-28
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- add **float calculateSpeedOfSound(float temperature, float humidity)**
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- redo lookup table SOS temperature humidity
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@ -44,7 +54,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
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- minor edits
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## [0.1.1] - 2021-11-18
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- update build-CI,
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- update build-CI
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- update readme.md
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- minor edits
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@ -18,15 +18,19 @@ Arduino library for the SRF05 distance sensor and compatibles.
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This library implements a API for a PING type of sensor.
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It is expected to work for quite a range of them.
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THe current version of the library only uses the SRF04 compatibility mode which uses a
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separate TRIGGER and ECHO pin.
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It does not (yet) implement the SRF05 mode in which TRIGGER and ECHO are the same.
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Till version 0.2.0 of the library, it only supported the SRF04 compatibility mode which uses a
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separate **TRIGGER** and **ECHO** pin.
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An important feature of this library is that it allows to adjust to the speed of sound (SOS).
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Version 0.3.0 implements support for the SRF05 mode in which **TRIGGER** and **ECHO** are the same.
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One need to connect the MODE pin to GND to select this mode in the device.
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Note that not all PING type of sensors will support the single pin mode.
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See also Connection section below.
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An important feature of this library is that it allows to adjust the speed of sound (SOS).
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Reasons to use a different value for the speed of sound is that it varies depending on
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temperature, humidity, composition of the air, air pressure, other type of gas, etc.
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Default value for the speed of sound is set to 340 m/s. (air, ~15°C, sea level pressure)
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Default value for the speed of sound is set to **340 m/s**. (air, ~15°C, sea level pressure)
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Since the version 0.2.0 the library has an interpolation formula to calculate the speed of sound
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given a temperature and humidity.
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@ -40,6 +44,12 @@ the **pulseIn()** function. This has in the end the same effect as changing the
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speed of sound however it is technically more correct to keep the two separated.
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#### Connection
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How to connect:
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- https://www.robot-electronics.co.uk/htm/srf05tech.htm
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#### Effect temperature and humidity
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Several correction formulas for the speed of sound are available on the internet
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@ -64,7 +74,7 @@ and wind speed. The latter is a bit compensated for, as the acoustic pulse will
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(table redone completely in 0.2.0)
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Temperature in Celsius, Humidity in %, constant pressure == 1013 mBar.
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Temperature in Celsius, Humidity in %, constant pressure == 1013 mBar, SOS in m/s.
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| temp | 0% | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% | 100% |
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|:----:|:------:|:------:|:------:|:------:|:------:|:------:|:------:|:------:|:------:|:------:|:------:|
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@ -107,6 +117,11 @@ This function returns a speed of sound with an overall error margin less than 1%
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lower than 0.5% compared to the numbers above.
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#### Related
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- https://www.robot-electronics.co.uk/htm/srf05tech.htm (good description of the sensor)
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## Interface
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```cpp
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@ -115,36 +130,49 @@ lower than 0.5% compared to the numbers above.
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#### Constructor
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- **SRF05(const uint8_t trigger, const uint8_t echo, const uint8_t out = 0)** constructor to set the trigger and echo pin.
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It is not clear what the purpose of the OUT pin is, effectively it is not used yet.
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- **SRF05(const uint8_t trigger, const uint8_t echo = 0)** constructor to set the trigger and echo pin.
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The echo pin can be left out, or set to the same as the trigger pin.
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In total one can do it in three ways.
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```cpp
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const int trigger = 7;
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const int echo = trigger;
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SRF05 SRF(trigger, echo);
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SRF05 SRF(trigger, trigger);
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SRF05 SRF(trigger);
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```
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To select single pin mode in the hardware the MODE pin of the device must be connected to GND.
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For the two pin (compatibility) mode the MODE pin must be left floating.
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#### Configuration
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- **void setSpeedOfSound(float sos)** adjust the speed of sound in meters per second (m/s).
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- **void setSpeedOfSound(float sos = 340)** adjust the speed of sound in meters per second (m/s).
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See table above.
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The function has **no range check** and accepts even negative values.
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This will cause a negative sign in the distances which can be handy sometimes when you have
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This will cause a negative sign in the distances which can be useful sometimes when you have
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two sensors in opposite directions.
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- **float getSpeedOfSound()** return set value (m/s)
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- **bool setCorrectionFactor(float factor = 1)** adjust the timing by a few percentage e.g. to adjust clocks.
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Typical values are between 0.95 and 1.05 to correct up to 5%.
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Should not be used to correct the speed of sound :)
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Returns false if factor <= 0.
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Returns false if factor is negative, <= 0.
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- **float getCorrectionFactor()** returns the current correction factor.
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#### Operational mode
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Normally a single read should be OK.
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Normally a single read should be sufficient, but the library has more modi.
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- **void setModeSingle()** read a single time.
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This is the default and typical the fastest.
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- **void setModeAverage(uint8_t count)** read count times and take the average.
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Note: between the reads there is a delay of 1 millisecond.
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Note: between the reads there is a default delay of 1000 microseconds.
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- **void setModeMedian(uint8_t count)** read count times and take the median.
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count must between 3 and 15 otherwise it is clipped.
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Note: between the reads there is a delay of 1 millisecond.
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Note: between the reads there is a default delay of 1000 microseconds.
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- **void setModeRunningAverage(float alpha)** use a running average algorithm
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with a weight alpha. Value for alpha depends on your application.
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Alpha must be larger than zero and smaller or equal to one. Alpha == <0..1]
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@ -152,15 +180,18 @@ Lower alpha averages great for static distances, a higher alpha is better
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suited for changing distances.
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- **uint8_t getOperationalMode()** returns the operational mode 0..3.
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See table below.
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- **void setSampleInterval(uint16_t microSeconds = 1000)** changes the interval used
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in **SRF05_MODE_AVERAGE** and **SRF05_MODE_MEDIAN**.
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Default is 1000 us == 1 milliSecond. Maximum is 65535 microseconds.
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- **uint16_t getSampleInterval()** return set interval.
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| Operational mode | Value | Notes |
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|:-------------------------|:-------:|:-------:|
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| SRF05_MODE_SINGLE | 0 | |
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| SRF05_MODE_AVERAGE | 1 | |
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| SRF05_MODE_MEDIAN | 2 | |
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| SRF05_MODE_RUN_AVERAGE | 3 | |
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| | other | error |
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| SRF05_MODE_SINGLE | 0 |
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| SRF05_MODE_AVERAGE | 1 | default sample interval 1000 us
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| SRF05_MODE_MEDIAN | 2 | default sample interval 1000 us
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| SRF05_MODE_RUN_AVERAGE | 3 |
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| | other | error
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If other modi are needed, please open an issue and I see if it fits.
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Of course one can create more elaborated processing of measurements
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@ -177,6 +208,7 @@ around this one.
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- **float getMeter()** returns distance in meter.
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- **float getInch()** returns distance in inches. (1 inch = 2.54 cm).
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- **float getFeet()** returns distance in feet. (1 feet = 12 inch).
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- **float getYards()** returns distance in yards. (1 yard = 3 feet = 36 inch).
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#### Experimental - setTriggerLength
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@ -262,10 +294,7 @@ See examples.
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- DHT22 and the formula for SOS
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- investigate effect of wind (speed of air) on the speed of sound.
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- investigate
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- should **setSpeedOfSound(float sos)** return bool if sos <=0 ?
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- value of **setTriggerLength()**
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- investigate switching between single pin (SRF05) mode and dual pin (SRF04) mode.
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- need a separate constructor.
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- investigate "guard time" between reads of 50 ms (20x /sec max).
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@ -274,12 +303,16 @@ See examples.
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- set default SOS to an SOS from the table instead of 340.
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- function **begin(T, H)** ?
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- add example to determine the correction factor?
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- delay(1) in average configurable?
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- add uint16_t **PulseTimeOut** = 200; // milliSeconds?
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- void setPulseTimeOut(uint16_t milliSeconds = 200);
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- uint16_t getPulseTimeOut();
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#### Wont
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- should **setSpeedOfSound(float sos)** return bool if sos <=0 ?
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- print feet as 3'2" or 3-7/8 feet (is that needed in this lib)
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- in printHelpers ?
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- see printHelpers lib **printFeet(float feet)**
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- fix magic conversion numbers.
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- add ```float lastValue()``` ?
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- not all paths update this variable.
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@ -1,7 +1,7 @@
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//
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// FILE: SRF05.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.2.0
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// VERSION: 0.3.0
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// DATE: 2021-05-17
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// PURPOSE: Arduino library for the SRF05 distance sensor (and compatibles)
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// URL: https://github.com/RobTillaart/SRF05
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@ -19,10 +19,12 @@ SRF05::SRF05(const uint8_t trigger, const uint8_t echo)
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_trigger = trigger;
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_echo = echo;
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_mode = SRF05_MODE_SINGLE;
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if (echo == 0)
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{
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_echo = _trigger;
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}
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pinMode(_trigger, OUTPUT);
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digitalWrite(_trigger, LOW);
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pinMode(_echo, INPUT);
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}
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@ -31,6 +33,7 @@ void SRF05::setSpeedOfSound(float speedOfSound)
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_speedOfSound = speedOfSound;
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}
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float SRF05::getSpeedOfSound()
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{
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return _speedOfSound;
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@ -42,13 +45,13 @@ bool SRF05::setCorrectionFactor(float factor)
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if (factor <= 0) return false;
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_correctionFactor = factor;
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return true;
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};
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}
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float SRF05::getCorrectionFactor()
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{
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return _correctionFactor;
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};
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}
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//////////////////////////////////////////////////
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@ -81,7 +84,6 @@ void SRF05::setModeMedian(uint8_t count)
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void SRF05::setModeRunningAverage(float alpha)
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{
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_mode = SRF05_MODE_RUN_AVERAGE;
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_count = 1;
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_alpha = alpha;
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@ -114,7 +116,7 @@ uint32_t SRF05::getTime()
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for (uint8_t s = 0; s < _count; s++)
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{
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sum += _read();
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delay(1);
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delayMicroseconds(_sampleInterval);
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}
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return round(sum / _count);
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}
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@ -125,7 +127,7 @@ uint32_t SRF05::getTime()
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for (uint8_t s = 0; s < _count; s++)
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{
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samples[s] = _read();
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delay(1);
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delayMicroseconds(_sampleInterval);
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}
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_insertSort(samples, _count);
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if (_count & 0x01) return samples[_count / 2];
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@ -170,6 +172,12 @@ float SRF05::getFeet()
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}
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float SRF05::getYards()
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{
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return _speedOfSound * getTime() * 0.54681e-6;
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}
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// EXPERIMENTAL
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// distance in meters (single trip)
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float SRF05::determineSpeedOfSound(float distance, uint8_t count)
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@ -179,7 +187,7 @@ float SRF05::determineSpeedOfSound(float distance, uint8_t count)
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while (count--)
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{
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sum += _read();
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delay(1);
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delayMicroseconds(_sampleInterval);
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}
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// sos = distance travelled forth and back in micrometer
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// divided by time in microseconds.
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@ -229,11 +237,16 @@ float SRF05::calculateSpeedOfSound(float temperature, float humidity)
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//
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uint32_t SRF05::_read()
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{
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// Send pulse
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pinMode(_trigger, OUTPUT);
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digitalWrite(_trigger, HIGH);
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delayMicroseconds(_triggerLength);
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digitalWrite(_trigger, LOW);
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uint32_t duration = pulseIn(_echo, HIGH, 300000);
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if (_correctionFactor == 1)
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// Wait for echo
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pinMode(_echo, INPUT);
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uint32_t duration = pulseIn(_echo, HIGH, 200000); // was 300000 (50+ meter)
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if (_correctionFactor == 1.0)
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{
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return duration;
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}
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@ -241,6 +254,7 @@ uint32_t SRF05::_read()
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}
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// for median
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void SRF05::_insertSort(uint32_t * array, uint8_t size)
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{
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uint8_t t, z;
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@ -260,5 +274,5 @@ void SRF05::_insertSort(uint32_t * array, uint8_t size)
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}
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// -- END OF FILE --
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// -- END OF FILE --
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@ -2,7 +2,7 @@
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//
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// FILE: SRF05.h
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// AUTHOR: Rob Tillaart
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// VERSION: 0.2.0
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// VERSION: 0.3.0
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// DATE: 2021-05-17
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// PURPOSE: Arduino library for SRF05 distance sensor
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// URL: https://github.com/RobTillaart/SRF05
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@ -10,7 +10,7 @@
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#include "Arduino.h"
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#define SRF05_LIB_VERSION (F("0.2.0"))
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#define SRF05_LIB_VERSION (F("0.3.0"))
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const uint8_t SRF05_MODE_SINGLE = 0;
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@ -22,7 +22,7 @@ const uint8_t SRF05_MODE_RUN_AVERAGE = 3;
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class SRF05
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{
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public:
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explicit SRF05(const uint8_t trigger, const uint8_t echo);
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explicit SRF05(const uint8_t trigger, const uint8_t echo = 0);
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// configuration
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@ -40,6 +40,9 @@ public:
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void setModeMedian(uint8_t count);
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void setModeRunningAverage(float alpha);
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uint8_t getOperationalMode();
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// interval of average and median mode
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void setSampleInterval(uint16_t microSeconds = 1000);
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uint16_t getSampleInterval();
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// get distance
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@ -49,6 +52,7 @@ public:
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float getMeter(); // m
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float getInch(); // inch = 2.54 cm
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float getFeet(); // feet = 12 inch
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float getYards(); // yard = 3 feet = 36 inch
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// Experimental - calibration
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@ -66,6 +70,7 @@ public:
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void setTriggerLength(uint8_t length = 10);
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uint8_t getTriggerLength();
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// TIMING
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uint32_t lastTime();
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@ -83,9 +88,11 @@ private:
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float _alpha = 1.0;
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float _value = 0;
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float _correctionFactor = 1;
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uint8_t _triggerLength = 10;
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uint8_t _triggerLength = 10; // microSeconds
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float _speedOfSound = 340; // 15°C 0%RH Sea level
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uint32_t _lastTime = 0;
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uint16_t _sampleInterval = 1000; // microSeconds
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uint32_t _read();
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void _insertSort(uint32_t * array, uint8_t size);
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@ -0,0 +1,49 @@
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//
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// FILE: SRF05_demo_single_pin.ino
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// AUTHOR: Rob Tillaart
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// PURPOSE: demo distance sensor
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// URL: https://github.com/RobTillaart/SRF05
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#include "SRF05.h"
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const int trigger = 7;
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const int echo = trigger;
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// SRF05 SRF(trigger, echo); // alternative
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// SRF05 SRF(trigger, trigger); // alternative
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SRF05 SRF(trigger);
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void setup()
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{
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Serial.begin(115200);
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Serial.println();
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Serial.println(__FILE__);
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Serial.print("SRF05_LIB_VERSION: ");
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Serial.println(SRF05_LIB_VERSION);
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Serial.println();
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SRF.setCorrectionFactor(1.035);
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}
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void loop()
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{
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Serial.println(SRF.getTime());
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delay(100);
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Serial.println(SRF.getMillimeter());
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delay(100);
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Serial.println(SRF.getCentimeter(), 1);
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delay(100);
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Serial.println(SRF.getMeter(), 2);
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delay(100);
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Serial.println(SRF.getInch(), 1);
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delay(100);
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Serial.println(SRF.getFeet(), 2);
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delay(1000);
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Serial.println();
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}
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// -- END OF FILE --
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@ -17,14 +17,19 @@ setModeMedian KEYWORD2
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setModeRunningAverage KEYWORD2
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getOperationalMode KEYWORD2
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setSampleInterval KEYWORD2
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getSampleInterval KEYWORD2
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getTime KEYWORD2
|
||||
getMillimeter KEYWORD2
|
||||
getCentimeter KEYWORD2
|
||||
getMeter KEYWORD2
|
||||
getInch KEYWORD2
|
||||
getFeet KEYWORD2
|
||||
getYards KEYWORD2
|
||||
|
||||
determineSpeedOfSound KEYWORD2
|
||||
|
||||
setTriggerLength KEYWORD2
|
||||
getTriggerLength KEYWORD2
|
||||
|
||||
|
||||
@ -15,7 +15,7 @@
|
||||
"type": "git",
|
||||
"url": "https://github.com/RobTillaart/SRF05.git"
|
||||
},
|
||||
"version": "0.2.0",
|
||||
"version": "0.3.0",
|
||||
"license": "MIT",
|
||||
"frameworks": "*",
|
||||
"platforms": "*",
|
||||
|
||||
@ -1,5 +1,5 @@
|
||||
name=SRF05
|
||||
version=0.2.0
|
||||
version=0.3.0
|
||||
author=Rob Tillaart <rob.tillaart@gmail.com>
|
||||
maintainer=Rob Tillaart <rob.tillaart@gmail.com>
|
||||
sentence=Arduino library for SRF05 distance sensor
|
||||
|
||||
Loading…
Reference in New Issue
Block a user