The author of the original project (dgatf aka DanielGA) has incorporated most of my modifications into his code and continues improving it. In most any cases you are likely better off with his code.
- correct #cells autodetection for normal and HV lipos
- correct EscA value from HW telemetry
- more filtering of invalid telemetry frames
- modified cells' voltage thresholds
- modified autodetection for rawCurrentOffset_
- tuned parameter ESCHW4_DIFFAMP_GAIN 16.9
- more sanity checks on incoming telemetry data
- millis() returns uint32_t : change everything related from uint16_t to uint32_t
The settings in config.h are tailored towards HW plat V4 80A esc and frsky smartport. Implementation is with arduino 328p, 8MHz, 3.3V.
(- also disabled some CASTLE code in smartport per #if 0 in order to fit debug code into arduino)
This is a DIY project to send sensors telemetry for a fraction of the weight and cost of the stock sensors. It adds support for several ESC telemetry protocols
Compatible RX protocols: Frsky Smartport, FrSky D, Spektrum XBUS, Spektrum SRXL V5, Flysky IBUS
Compatible ESCs: Hobbywing V3/V4/V5, Kontronik, Castle Link
Compatible MCUs: ATmega328P, ATmega328PB, ATmega2560 and ATmega32U4 and Teensy LC/3.x
Implemented sensors:
- ESC
- ESCs with serial telemetry (Hobbywing V3/V4/V5, Kontronik)
- ESC with PWM signal or phase sensor
- ESC Castle Link
- GPS serial (NMEA)
- I2C sensors: BMP280
- Analog sensors: voltage, temperature, current, air speed
All sensors are optional. Make the circuit with the desired sensors and enable them in the configuration, with a lua script if using smartport or in config.h for the rest of Rx protocols
| MCU | Recommended board | Castle telemetry | UART(1) | Inverted UART(2) |
|---|---|---|---|---|
| ATmega328P | Arduino Pro Mini(5) | Innacurate | 1 | ❌ |
| ATmega328PB | Pololu ATmega328PB(5) | ✅ | 2 | ❌ |
| ATmega2560 | ATmega2560 Pro Mini | ✅ | 4 | ❌ |
| ATmega32U4(3) | Teensy 2 | ✅ | 1 | ❌ |
| ARM CortexM0+ | Teensy LC(4) | ✅ | 3 | ✅ |
| ARM CortexM4 | Teensy 3.2 | ✅ | 3 | ✅ |
(1) 2 x UARTS allows to use ESC serial and GPS at the same time
(2) Allows to use hardware serial for Smartport
(3) Arduino Micro is not supported
(4) Teensy LC is not 5v tolerant. If using with Castle is preferred Teensy 3.2, which is 5v tolerant
(5) Arduino Pro Mini and Pololu ATmega328PB requires a USB-TTL programmer for flashing
ATmega boards at 5v (16Mhz) may not read properly serial port when using ESC serial or GPS as they use 3.3v logic level and Arduino 5v. In this case if using 5v it is better without USB (Pro Mini) and/or use software serial. If using ATmega board, is preferred 3.3v (8Mhz) boards
| Board | Arduino Pro Mini | Pololu ATmega328PB | Arduino ATmega2560 | Teensy 2 | Teensy LC Teensy 3.x |
|---|---|---|---|---|---|
| MCU | ATmega328P | ATmega328PB | ATmega2560 | ATmega32U4 | ARMCortexM0+ ARMCortexM4 |
| NTC 1 | A0 | A0 | A0 | F6(A1) | 14 |
| NTC 2 | A1 | A1 | A1 | F7(A0) | 15 |
| Voltage 1 | A2 | A2 | A2 | F5(A3) | 16 |
| Voltage 2 | A3 | A3 | A3 | F4(A2) | 17 |
| Current | A6 | A6 | A6 | B5(A9) | 20 |
| Airspeed | A7 | A7 | A7 | D7(A7) | 26 |
| ESC serial | RX | RX0 | 19 | D2(RX1) | 9 |
| GPS | RX | RX1 | 17 | D2(RX1) | 7 |
| PWM in | 8 | 8 | 49 | D4(A6) | 6 |
| PWM out | 10 | 10 | 7 | B6(A10) | 22 |
| Rx Castle | 8 | 8 | 49 | C7 | 16 |
| ESC Castle(1) | 2 & 10 | 2 & 22 | 45 & 48 | C8 & B6 | 22 & 6 |
| Frsky D, Smartport or SRXL | 7 & 12(2) | 4 & 23(2) | 10 & 15(2) | B2 & B4(2) (16 & 8) |
0 & 1(2) |
| XBUS or sensor SDA | A4 | A4 | 20 | D1(2) | 18 |
| XBUS or sensor SCL | A5 | A5 | 21 | D0(3) | 19 |
(1) with pull up 3.3k
(2) with resistor 3.3k
The following Rx protocols are supported:
- Frsky Smartport : inverted serial, 57600 bps
- Frsky D : inverted serial, 9200 bps
- Spektrum SRXL V5: serial, 115200 bps
- Spektrum XBUS: I2C
- Flysky IBUS: serial, 115200 bps
Depending on the receiver protocol connect to the Rx as follows
Frsky D, Smartport, SRXL or IBUS
Frsky D: Signal = Rx
XBUS
Compatible ESC serial protocols: Hobbywing V3/V4/V5 and Kontronik
Optionally a PWM signal can be generated from the RPM value in serial telemetry
ESC serial
Remark:
- In HW V3 the telemetry port is the program port. It is a servo male plug on the ESC
- In HW V4/V5 the telemetry port is a wired servo female plug. Don't confuse with RPM PWM signal connector or the program port
- For HW ESCs be sure the firmware installed is NOT VBAR version
If the ESC have a PWM signal or a phase sensor is installed, RPMs can be measured. If ESC have both serial and PWM signal, like Hobbywing V4/V5, then PWM signal is not needed for telemetry
PWM signal/phase sensor circuit
The telemetry is send over the ESC signal. Castle Link has to be enabled in the ESC config
If using ATmega328P telemetry values are not accurate all the time. Some readings are increased by 5-10%. This is a hardware limitation
Castle Link with Smartport
| Model | RPM | Throttle | Motor PWM | Voltage | Current | Voltage BEC | Current BEC | Temperature 1 | Temperature 2 | Ripple Volt |
|---|---|---|---|---|---|---|---|---|---|---|
| Hobbywing V3 | ✅ | ✅(1) | ✅(1) | |||||||
| Hobbywing V4/V5(4)(5) | ✅ | ✅(1) | ✅(1) | ✅ | ✅(2) | ✅ FET | ✅ BEC | |||
| Castle Link | ✅ | ✅(1) | ✅(1) | ✅ | ✅ | ✅(3) | ✅(3) | ✅ | ✅ | |
| Kontronik | ✅ | ✅(1) | ✅(1) | ✅ | ✅ | ✅ | ✅ | ✅ Power amp | ✅ BEC |
(1) Available but not forwarded to smartport
(2) For 80A models and higher
(3) Not available in all models
(4) Sensors varies depending on model and firmware. See annex
(5) Upgrade to latest firmware version. But note VBAR versions of firmware are not compatible. Install a non VBAR version of the ESC firmware
If voltage is available the cell voltage average is calculated for 3S,4S,5S,6S,7S,8S,10S and 12S batteries. 10 seconds after power on the number of cells is autodetected. Average cell voltage to be >3.8v for correct cell count
Serial GPS (NMEA protocol) is supported
The following analog sensors are supported:
- 2 x voltage divider
- 2 x temperature sensors (thermistors)
- Current sensor (Hall effect)
- Airspeed sensor (MPXV7002)
I2C sensors not compatible with XBUS. The following I2C sensors are suported:
- Barometer: BMP280
Remark:
For BMP280 module there are two versions: 3.3V (6 pins, I2C/SPI) and 5V (4 pins, I2C). Note that 3.3V version is not 5V tolerant. Use module version accordingly to your board Vcc
I2C and analog sensors with Smartport
Using Arduino IDE copy folder msrc and open msrc.ino. Select the board and flash
The configuration is modified with a lua script (X7, X9, X-lite and Horus with openTx 2.2 or higher)
Copy the file msrc.lua to the SCRIPTS/TOOLS folder. (if using older openTx 2.2 copy to SCRIPTS folder and execute by long press)
If not using lua script comment #define CONFIG_LUA and assign config values in msrc.h
Options:
- ESC protocol. HobbyWing Platinum V3, HobbyWing Platinum V4/Hobbywing Flyfun V5 or PWM signal
- Voltage1. Enable/disable analog voltage divider 1
- Voltage2. Enable/disable analog voltage divider 2
- Ntc1. Enable/disable analog thermistor 1
- Ntc2. Enable/disable analog thermistor 2
- Current. Enable/disable analog current
- Airspeed. Enable/disable analog airspeed sensor
- PWM out. Enable/disable analog a PWM signal from RPM values from ESC serial
- GPS. Enable/disable serial GPS
- Averaging queue size: 1 to 16
- Refresh rate (ms): 0 to 1600
- I2C (x2). Sensor type and address
Configuration is done in config.h
The default sensor id is 10. This can be changed with change_id_frsky
Depending on your configuration some the following sensors will be available in Opentx. After configuration go to sensors screen and update with Search new sensors
ESC:
- ESC RPM: Erpm (0x0b60)
- ESC voltage: EscV (0x0b50)
- ESC cell average: VFAS (0x0210)
- ESC current: EscA (0x0b50)
- ESC temp FET (HW) or ESC temp linear (Castle): EscT (0x0b70)
- ESC temp BEC (HW) or ESC temp NTC (Castle): EscT (0x0b71)
- ESC ripple voltage: EscV (0x0b51)
- ESC BEC voltage: BecV (0x0e50)
- ESC BEC current: BecC (0x0e50)
GPS:
- GPS Lat/Lon: GPS (0x800)
- GPS altitude: GAlt (0x820)
- GPS speed: GSpd (0x820)
- GPS compass: Hdg (0x840)
- GPS date/time: Date (0x850)
Analog:
- Voltage 1: A3 (0x0900)
- Voltage 2: A4 (0x0910)
- Thermistor 1: Tmp1 (0x0400)
- Thermistor 2: Tmp2 (0x0410)
- Current: Curr (0x020f)
- AirSpeed: ASpd (0x0a00)
I2C:
- Altitude: Alt (0x0820)
- Temperature: T1 (0x0401, 0x0402)
Some of the sensors have to be adusted in openTx
- Blades/poles: number of pair of poles * main gear teeth
- Multiplier: pinion gear teeth
Measure the voltage of the battery with a voltmeter and adjust Ratio in A3, A4 sensor
If using a hall effect sensor, adjust the ratio: 25.5 x 1000 / output sensitivity (mV/A)
To calculate the battery consumption add a new sensor:
- Type: Calculated
- Formula: Consumption
- Sensor: Curr
HW V4/V5 uses few different offsets to measure the current. It have been detected two types, V4 and V5, but there seems to be more types
Current value should be close to 0 A without blades and throttle at 50%. If this is not the case you can calibrate the current sensor (EscA) in opentx (sensor->edit sensor->offset) by adjusting the offset with the value at this condition (no blades and 50% throttle)
MSRC on Align 450 connected to Hobbywing V3 Platinum and two thermistors for ESC and motor
Serial parameters:
- 19200 bps
- 1 packet every 20 ms
- Big endian
| Byte | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Value | Package Head (0x9B) | Package Number 1 | Package Number 2 | Package Number 3 | Rx Throttle 1 | Rx Throttle 2 | Output PWM 1 | Output PWM 2 | RPM Cycle 1 | RPM Cycle 2 |
RPM = 60000000 / RPM Cycle
thr, pwm: 0-255 (8bits)
| Byte | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Value | Package Head (0x9B) | Package Number 1 | Package Number 2 | Package Number 3 | Rx Throttle 1 | Rx Throttle 2 | Output PWM 1 | Output PWM 2 | RPM 1 | RPM 2 | RPM 3 | Voltage 1 | Voltage 2 | Current 1 | Current 2 | TempFET 1 | TempFET 2 | Temp 1 | Temp 2 |
thr, pwm: 0-1024 (10bits)
Voltage, current and temperature are raw sensor data. Actual values requires transformation. Depending on the model, sensors are different so the transformations:
- Voltage divider. Different for LV and HV models. LV divisor 11. HV divisor 21
- Current sensor (shunt resistor and diff amp). Different for V4 and V5. V5 seems to be shifted by Vref=0.53V. See 4.4 Calibrate current sensor HW V4/V5
- Temperature. NTC resistor. So far it is the same for tested models
Before throttle is raised from 0, signature packets are sent between telemetry packets. This is used to identify the hardware and firmware of the ESC
Examples:
| Model\Byte | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| V4LV25/60/80A | 0x9B | 0x9B | 0x03 | 0xE8 | 0x01 | 0x08 | 0x5B | 0x00 | 0x01 | 0x00 | 0x21 | 0x21 | 0xB9 |
| V4HV200A OPTO | 0x9B | 0x9B | 0x03 | 0xE8 | 0x01 | 0x02 | 0x0D | 0x0A | 0x3D | 0x05 | 0x1E | 0x21 | 0xB9 |
| V5HV130A OPTO | 0x9B | 0x9B | 0x03 | 0xE8 | 0x01 | 0x0B | 0x41 | 0x21 | 0x44 | 0xB9 | 0x21 | 0x21 | 0xB9 |
For best accuracy RX pulse input is captured with a timer interrupt and ESC pulse output is produced by hardware PWM. Maximum latency is 20ms
See Castle Link Live
For best accuracy PWM signal output for FBL is produced by hardware PWM from serial RPM values. Maximum latency is 40ms
To obtain the voltage at the analog pin it is required the ADC bits (b) and the Vref:
Two battery voltages can be measured through the analog pins A2 and A3 Metal resistors are recommended as gives more accurate readings (0.1W or higher) Arduino can read up to 3.3V/5V and is optimized for signal inputs with 10K impedance
To select R values apply formulas:
For 6S battery (or lower) and Pro Mini 3.3v:
- R1 68k
- R2 10k
If more than 6S change R values or you may burn the Arduino!
Two temperature sensors can be installed through the analog pins A0 and A1 Temperature is measured with NTC thermistors (100k). Adjust thermistor Beta in ntc.h if needed (NTC_BETA, default is 4190). Sensor output in Celsius
To obtain the thermistor resistance:
And temperature with Beta formula:
Or with Steinhart and Hart Equation if data is available:
Hall effect sensors. Induced magnetic field is transformed into voltage. They are caracterized by their sensitivity
The voltage drop in the shunt resistor is amplified by a differential amplifier to obtain Vo
Air speed is measured with a differential pressure sensor
Presssure is calculated with the sensor's transfer formula:
And the air speed using the Bernouilli formula:
After 2 seconds the sensor is calibrated to zero
Adjust constants in pressure.h:
- TRANSFER_SLOPE (B) as per sensor datasheet
- For fine tuning measure the Vcc on the sensor and adjust TRANSFER_VCC
0.8
- Added Rx protocols Frsky D, Spektrum XBUS, Spektrum SRXL V5, Flysky Ibus
- Added support for ATmega328PB, ATmega2560, ATmega32U4, ARM Cortex M0+ and ARM Cortex M4
- Improved accuracy for PWM input (rpm) measurement
- Added support for Kontronik ESC
- Added analog airspeed sensor (MPXV7002)
- Fixed Castle Link bug
- Removed BMP180
- Fixed flickering in color lcd displays
- Added GPS serial (BN220, BN880, NEO-M8N,...)
- Added Castle Link Live protocol
- Hobbywing V4/V5. Improved transformations for voltage and current depending on the model (thanks to Commodore8888)
- Fix Horus display
- Changed R3 resistor to 3.3k
- Support for change_id_frsky to change the sensor id
- Support for I2C sensors
- Improved code quality and performance
- Smartport_library improved performance and abstract from the smartport protocol
- Added cell voltage average (HW V4/V5, VFAS sensor)
- Applied correct transformation for esc voltage, current and temperature (HW V4/V5)
- Changed averaging type from SMA to EMA
- Added esc protocol NONE
- Smartport protocol. Minor improvements
- Esc current sensor (EscA) added (HW V4/V5, 80A or higher)
- Averaging telemetry added
- Voltage2 sensor changed from A3 to A4
- Ntc2 sensor changed from Tmp1 to Tmp2
- Averaging governor added
- Refresh rate and averaging added to lua config script
For questions, issues or new protocol request (use this sketch) please post in the forums:
Or open an Issue in Github
- DanielGA (Helifreak)
- Commodore8888 (Helifreak)
- MikeJ (Helifreak)