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130 lines
6.2 KiB
Markdown
130 lines
6.2 KiB
Markdown
# ThunderFly TFRPM01 Revolution Counter
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The [TFRPM01](https://github.com/ThunderFly-aerospace/TFRPM01) tachometer is a small, and low system demanding revolution-counter.
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The board itself does not include the actual sensor but can be used with many different sensors/probe types for revolution counting.
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It has an I²C connector for connecting to PX4 and is connected to the actual sensor via a 3-pin connector.
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It also has an LED that offers basic diagnostic information.
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::: info
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The TFRPM01 sensor is open-source hardware commercially available from [ThunderFly s.r.o.](https://www.thunderfly.cz/) (manufacturing data is [available on GitHub](https://github.com/ThunderFly-aerospace/TFRPM01)).
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:::
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## Hardware Setup
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The board is equipped with (two through pass) I²C connectors for connecting to PX4 and has a 3-pin connector that can be used to connect to various sensors:
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- TFRPM01 may be connected to any I²C port.
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- TFRPM01 has a 3pin pin-header connector (with pull-up equipped input) that can be connected to different probe types.
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- The sensor/probe hardware needs a pulse signal.
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The signal input accepts +5V TTL logic or [open collector](https://en.wikipedia.org/wiki/Open_collector) outputs.
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The maximum pulse frequency is 20 kHz with a 50% duty cycle.
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- The probe connector provides a +5V power supply from the I²C bus, the maximum power which could be used is limited by RC filter (see schematics for details).
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TFRPM01A electronics is equipped with signaling LED that can be used to check that the probe is connected properly.
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The LED lights up when the pulse input is grounded or exposed to logical 0, so you can check the probe is working correctly just by manually spinning a rotor.
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### Hall-Effect Sensor Probe
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Hall-Effect sensors (magnetically operated) are ideal for harsh environments, where dirt, dust, and water can contact the sensed rotor.
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Many different hall effect sensors are commercially available.
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For example, a [55100 Miniature Flange Mounting Proximity Sensor](https://www.littelfuse.com/assetdocs/littelfuse-hall-effect-sensors-55100-datasheet?assetguid=6d69d457-770e-46ba-9998-012c5e0aedd7) is a good choice.
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### Optical Sensor Probe
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An optical sensor can also be used (and may be a better fit, depending on the measurement requirements).
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Both transmissive and reflective sensor types may be used for pulse generation.
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## Software Setup
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### Starting driver
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The driver is not started automatically (in any airframe).
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You will need to start it manually, either using the [QGroundControl MAVLink Console](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/analyze_view/mavlink_console.html) or by adding the driver to the [startup script](../concept/system_startup.md#customizing-the-system-startup) on an SD card.
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#### Start driver from console
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Start the driver from the [console](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/analyze_view/mavlink_console.html) using the command:
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```sh
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pcf8583 start -X -b <bus number>
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```
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where:
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- `-X` means that it is an external bus.
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- `<bus number>` is the bus number to which the device is connected
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::: info
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The bus number in code `-b <bus number>` may not match the bus labels on the autopilot.
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For example, when using CUAV V5+ or CUAV Nano:
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| Autopilot label | -b number |
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| --------------- | --------- |
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| I2C1 | -X -b 4 |
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| I2C2 | -X -b 2 |
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| I2C3 | -X -b 1 |
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The `pcf8583 start` command outputs the corresponding autopilot bus name/label for each bus number.
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:::
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### Testing
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You can verify the counter is working using several methods
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#### PX4 (NuttX) MAVLink Console
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The [QGroundControl MAVLink Console](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/analyze_view/mavlink_console.html) can also be used to check that the driver is running and the UORB topics it is outputting.
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To check the status of the TFRPM01 driver run the command:
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```sh
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pcf8583 status
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```
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If the driver is running, the I²C port will be printed along with other basic parameters of the running instance.
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If the driver is not running it can be started using theprocedure described above.
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The [listener](../modules/modules_command.md#listener) command allows you to monitor RPM UORB messages from the running driver.
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```sh
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listener rpm
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```
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For periodic display, you can add `-n 50` parameter after the command, which prints the next 50 messages.
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#### QGroundControl MAVLink Inspector
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The QGroundControl [Mavlink Inspector](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/analyze_view/mavlink_inspector.html) can be used to observe MAVLink messages from PX4, including [RAW_RPM](https://mavlink.io/en/messages/common.html#RAW_RPM) emitted by the driver:
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1. Start the inspector from the QGC menu: **Analyze tools > Mavlink Inspector**
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1. Check that `RAW_RPM` is present in the list of messages (if it is missing, check that the driver is running).
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### Parameter Setup
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Usually, sensors can be used without configuration, but the RPM values should correspond to multiples of real RPM. It is because the `PCF8583_MAGNET` parameter needs to correspond to the real number of pulses per single revolution of the sensed rotor.
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If needed, the following parameters should be tweaked:
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- [PCF8583_POOL](../advanced_config/parameter_reference.md#PCF8583_POOL) — pooling interval between readout the counted number
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- [PCF8583_RESET](../advanced_config/parameter_reference.md#PCF8583_RESET) — Counter value where the counted number should be reset to zero.
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- [PCF8583_MAGNET](../advanced_config/parameter_reference.md#PCF8583_MAGNET) — Number of pulses per revolution e.g. number of magnets at a rotor disc.
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::: info
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The parameters above appear in QGC after the driver/PX4 are restarted.
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If the configuration parameters are not available after restart then you should check that the driver has started.
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It may be that the [driver is not present in the firmware](../peripherals/serial_configuration.md#configuration-parameter-missing-from-qgroundcontrol), in which case it must be added to the board configuration:
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```sh
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drivers/rpm/pcf8583
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```
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:::
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