User Manual
Contents
1. T REX RODOT COoOmMmTROL LLERA Bluetooth or FTDI 38 Eie Power In TTL Serial re T a Regulator V GND EP USBL oe eee Siki SCL LED Pey Ss serie SDALED CND rt rCc gt External SDA Taa aii Te e aly 3 ee VII St e ii G en a 3 i V Acopetomets SEL 2 sap C a oi Switch lect 3 Short for ata 3V3 s5 3 ISP 21 3 c Encoder or RC tima sv Gnd Servos 7 ee OND Left Motor moo Right Motor motor Low Voltage fault f Mmi ev saat ond voasa Power Out Output gt Output tc Introduction The T REX controller from DAGU is an Arduino compatible robot controller designed to power and control servos and brushed motors Supplied sample code allows the controller to connect to a radio control receiver external controller via C or optional bluetooth interface A sample app allows the controller to be controlled by an Android phone or tablet The ATmega328P controller comes with the Arduino bootloader and customer software can be uploaded via the built in USB interface ISP or FTDI sockets The Dual H bridges are rated for stall currents of 40A per motor and average currents of 18A per motor Factory calibrated hall effect sensors measure current draw of each motor Each motor has independent variable electronic braking Self resetting PTC fuses prevent damage from stalled motors The built in switch mode power supply allows the controller to work over a wide range of voltages fr2. C interfacing rc gt Connect the V SCL SDA and Gnd of the external logic to the VI SCL SDA and GND pins of the T REX I C interface The T REX will automatically translate the voltage The interface includes 10K pullup resistors although external pullup resistors can be added if required When using C mode for the first time the TREX controller joins the 12C IPC bus as a slave device with the address 0x07 decimal 7 This can be changed using the command data packet and the new address will be stored in the controllers EEPROM The 1 C clock speed is 100kHz on start up but can be changed to 400kHz with the command data packet Command data packets consist of 27 bytes and provide full control over the motors and servos as well as configuration settings Status data packets consist of 24 bytes and provide an error flag battery voltage motor currents encoder counts angle and impact data Command Data Packet When an external controller wants to control the T REX then it must send 27 bytes of data as listed below DOS ON ae A or NNN NO NN DN N PM RR RRR RK RK kK kK Oo NYDN BPWNRK DUO WANDA NA KWNKY CO Start byte must be Ox0F 15 decimal PWM frequency a number from 1 to 7 to select motor PWM frequency Left motor speed high byte Left motor speed low byte Left motor brake O brake off 1 brake on Right motor speed high byte Right motor speed low byte Right motor brake O brake off 1 brake on
3. Servo 0 position high byte Servo 0 position low byte Servo 1 position high byte Servo 1 position low byte Servo 2 position high byte Servo 2 position low byte Servo 3 position high byte Servo 3 position low byte Servo 4 position high byte Servo 4 position low byte Servo 5 position high byte Servo 5 position low byte Accelerometer de vibrate 0 255 default 50 Impact sensitivity high byte impact sensitivity low byte lowbat high byte lowbat low byte PC address 0 127 Clock frequency 0 100kHz 1 400kHz Start byte this is a simple method of error checking If the start byte is not OxOF or the Master does not send 27 bytes then the receiving buffer is flushed of potentially corrupt data and bit O of the error flag is set The external controller should request a status update after sending command data to check the error flag PWM frequency Timer 2 is used to control the PWM Pulse Width Modulation frequency of the dual H bridge By default this set to 122Hz Many smaller motors cannot work efficiently at high frequencies because their inductive reactance increases with frequency and limits the flow of current The full range of PWM frequencies are 1 2 3 4 5 6 7 31250Hz Silent but many motors will have poor torque and can overheat 3906Hz Not recommended high pitch noise and poor torque 977Hz Not recommended too much noise 488Hz Not recommended too much
4. GPS Compass and Camera with the sensors on the controller for a mobile phone controlled robot Note The blue tooth module should be disconnected when uploading new code using the USB or FTDI interfaces as they share the same serial interface Uploading Code using either USB ISP or FTDI The TREX controller can be powered and programmed by USB ISP and FTDI interfaces The controller can be powered by these interfaces for the purpose of uploading new code although motor and accelerometer functions will be disabled Note although the ISP socket can be used for burning the bootloader overwriting the bootloader and uploading code directly it is not suitable for interfacing other ISP devices as some of it s pins are dedicated to motor control functions Battery power should be turned off when uploading new code to prevent unexpected movement from the robot Sample Code The T REX robot controller comes pre loaded with the Arduino Nano w 328 bootloader and sample code that lets you use the controller right out of the box The sample code was written and can be edited using the Arduino IDE 1 04 This software can be downloaded here http arduino cc en Main Software The T REX controller uses the CP2102 USB interface from Silicon Labs Drivers for Windows Macintosh and Linux can be downloaded here http www silabs com products mcu Pages USBtoUARTBridgeVCPDrivers aspx Primary Controller The PREX can be used as the primary c
5. noise 244Hz Not recommended too much noise 122Hz Default setting Good torque low noise 31Hz Best torque but more vibration Motor speed This is a value from 255 to 255 Negative values indicate a reverse direction Motor brake When this byte is non zero electronic braking occurs In brake mode the motor speed controls braking Negative speed values are treated as positive values when braking so that a motor speed of 255 or 255 will both equal 100 brake Servo positions 0 5 A maximum of 6 servos can be controlled by the T REX controller A value of 1500 is equal to a pulse with a width of 1500uS which will centre the servo Typically the servo position should be a value between 1000 and 2000 although it will vary depending on the servos used Negative values will move the servo the same as positive values except the sense of direction will be reversed A value of 0 indicates no servo connected and no control pulses will be sent to that pin De vibrate After an impact occurs the chassis may continue to vibrate for a short time and this could lead to false triggering The de vibrate variable sets a time period in 2mS units where impact sensing is temporarily disabled The default setting is 50 which equals a time period of 100mS Impact Sensitivity There is always acceleration and vibration when a robot moves The sample code looks for sudden changes in accelerometer readings over a 2mS period to indicate an impact h
6. Fuse trip current 23 C Fuse maximum current 23 C Electronic braking current Accelerometer Type Voltage Number of axes Sensitivity Output USB interface Type Drivers for Windows Macintosh and Linux ATmega328P 16MHz 5V 32K 2K 1K Arduino Nano w ATmega 328 6V 30V 20A continuous 110A peak 6V 3A maximum 52kHz 2A continuous 3A peak Motors powered directly from battery 9A continuous 40A peak Sensitivity 100mV Amp 30V 9A self resetting PTC 0 0059 0 0200 9A continuous 18A minimum 40A maximum 85A maximum MMA7361L Freescale Semiconductor 3 3V 3 1 5g or 6g Analog amplified from 3 3V to 5V scale CP2102 Silicon Labs http www silabs com products mcu Page s USBtoUARTBridgeVCPDrivers aspx Typical PTC fuse response time ime in Ti 1 10 Current in Amperes The average time current curves and Temperature Rerating curve performance is affected by a number or variables and these curves provided as guidance only Customer must verify the performance in their application
7. ample code mixes the steering and throttle channels by default to produce left and right motor speeds This can be changed by editing the code in the tab RCmode Bluetooth Mode If no RC signals are detected on power up the sample code will then check if the DAGU bluetooth module is connected This small low cost module plugs directly into the PCB If necessary it can be mounted away from the PCB for better signal reception using the supplied 4 wire cable If the bluetooth module is detected the sample code will automatically set the baud rate to 9600 the name to T REX and the pin number to 1234 Wait for at least 6 seconds after turning on the T REX controller before you start the T REX Android app This allows time for the controller to configure the bluetooth module Touching the dinosaur head will open an options box to allow you to scan for and select the T REX bluetooth interface Once selected wait a few seconds for the message T REX connected to appear You can now use the left and right sliders to control the left and right motors Releasing the sliders will cause them to automatically return to stop position If the T REX controller detects an impact then the phone will vibrate IC Mode This is the preferred method of control when using an external controller All of the controller functions are available in this mode when using the sample code One 4 wire female to female cable is supplied for
8. as occurred Adjust the sensitivity to prevent false triggering due to vibration or rough terrain Values greater than 0 are used to change the sensitivity setting The default is 50 Low Battery Voltage Some batteries can be damaged if their voltage falls too low The TREX controller will automatically shut down if the battery voltage is too low A value between 550 and 3000 will set the minimum safe voltage between 5 5V and 30V By selecting a value higher than the battery voltage you can force a shut down PC address The default I C address is 0x07 7 decimal but this can be changed at any time The address is stored in EEPROM memory so it is not forgotten when the power is turned off PC clock frequency When power is first applied or the controller is reset then the 1 C clock frequency will default to 100kHz By setting this byte to a non zero value the clock frequency can be changed to 400kHz Note After changing the I C clock frequency the master must change it s clock frequency to match Status Data Packet The I C master can request a status update from the T REX controller at any time The T REX will return 24 bytes of data as listed below Start byte will be OxFO 240 decimal Error flag 0 indicates the last command packet was received ok Battery voltage high byte Battery voltage low byte Left motor current high byte Left motor current low byte Left encoder count high byte Left encoder count low byte Right mot
9. oftware to control the speed direction and electronic braking of each motor individually The PWM frequency has several software selectable settings from 30 5Hz to 31250Hz The default frequency is 122Hz as not all motors can operate efficiently at higher frequencies Factory calibrated hall effect current monitoring sensors allows software to deal with dangerous stall conditions where high currents could otherwise damage the motors or exceed the safe limit of the battery Self resetting PTC fuses provide additional protection in extreme circumstances The fuses can handle short term overloads and surges when a motor starts or reverses suddenly without tripping The slow response time of these fuses allow the software time to handle the situation The PTC fuses have a maximum rating of 40A each Fault LEDs will light up if a fault condition such as battery voltage too low occur Turn power off for a few seconds and the turn on again to clear the fault Encoders In PC mode encoders can be connected to digital pins D5 and D6 make sure servo positions 4 amp 5 are set to 0 to disable servo pulses The sample code will monitor these pins and count all state changes If the motor is going forward the count will increase If the motor is going in reverse the count will decrease Applying the brake when motor speed is 0 will reset the count for that motor 3 Axis Accelerometer The T REX controller includes a 3 axis accelerometer on analog in
10. om 6V 30V and delivers 3A of current at 6V for driving servos The 5V LDO regulator can deliver in excess of 2A if required for powering an external controller A built in 3 axis accelerometer provides robots with angle acceleration and impact data Contents Power Heat Dissipation Low Voltage Mode High Voltage Mode Dual H Bridges Encoders 3 Axis Accelerometer IC Interface Servos Bluetooth Uploading Code Sample Code Primary Controller Radio Control Mode Bluetooth Mode C Mode Command Data Packet Start byte PWM frequency Motor speed Motor brake Servo positions 0 5 De vibrate Impact sensitivity IC clock frequency Status Data Packet Start byte Error flag Battery voltage Motor current Encoder count Accelerometer readings Impact readings Specifications ODMDOANDAAAAAHKRA HR HRWWWW Power The TREX controller is rated for a maximum voltage of 30V and can handle currents in excess of 40A per motor Note Although rated for 30V a 24V SLA battery will typically be 28 4V when fully charged and may exceed 30V when fast charging so make sure that your system will not exceed 30V or disconnect the batteries when charging A high current FET is used for switching power allowing low current power switches to be used The PREX controller includes a battery monitor on A3 The sample code will shut down if the battery voltage falls below 5 5V but this value can be changed in I2C mode or by editing the
11. ontroller for a robot As the sample code was written with the Arduino IDE it can be easily modified or replaced to suit your needs As the only spare I O pins are normally used for servos and encoders the best way to add more sensors and devices is via the I C interface Advanced users may wish to incorporate the GPS compass camera and WiFi capabilities of a mobile phone using the optional bluetooth module Radio Control Mode RC mode is the simplest method of control with the T REX controller behaving as a motor controller and BEC Two 3 wire female to female cables are recommended for connecting your RC receiver to the TREX controller Note the recommended cables will power the receiver from 5V when connected as shown If you wish to power the receiver and additional servos from a different voltage then remove the red wire from the cables to prevent damage The sample code automatically looks for RC control signals when power is first applied This means your radio transmitter should be turned on before you turn on the robot The motors will quietly beep 3 times to indicate RC mode is selected If the signal is lost while in RC mode then the motors will shut down until the signal returns Connect the receiver throttle channel to D5 and the steering channel to D6 The receiver should be powered from 5V to prevent damage to the T REX controller As the T REX tank chassis and most other robot chassis s use skid steering the s
12. or current high byte 10 Right motor current low byte 11 Right motor encoder count high byte 12 Right motor encoder count low byte 13 Accelerometer X axis high byte 14 Accelerometer X axis low byte 15 Accelerometer Y axis high byte 16 Accelerometer Y axis low byte 17 Accelerometer Z axis high byte 18 Accelerometer Z axis low byte 19 Impact X axis high byte 20 Impact X axis low byte 21 Impact Y axis high byte 22 Impact Y axis low byte 23 Impact Z axis high byte 24 Impact Z axis low byte Oe ON Eco a Start byte This byte should be OxOF 15 decimal If not then clear the buffer wait at least 2mS and repeat the status requested again Error flag A non zero value indicates the previous command data packet contained errors Different bits are set depending on the nature of the error BIT 0 Start byte not received or incorrect data packet size BIT 1 PWM frequency was not 1 7 BIT 2 Left or right motor speed was not 255 to 255 BIT 3 One or more servo positions was not 2400 to 2400 BIT 4 Impact sensitivity not 0 1023 BIT 5 Low battery was not 550 to 3000 5 5V to 30V BIT 6 I C slave address was not 0 127 BIT 7 I C speed not 0 or 1 100kHz or 400kHz If bits O or 2 are set then the motors will shut down to prevent a possible collision Battery voltage An integer that is 100x the actual voltage This gives a precision of 0 01V so that a value of 1527 would equal 15 27V Motor current Current drawn b
13. puts AO A2 The sample code provided uses this sensor to determine direction and magnitude of impacts Raw sensor data is also available to external controllers for determining the angle and acceleration of the robot The default sensitivity setting for the accelerometer is 1 5g but shorting the SG pins with a jumper will change the sensitivity to 6g IC Interface The PREX controller has an C interface with automatic voltage translation for logic voltages from 1 8V to 5V This allows the controller to be slaved to a wide range of external controllers The sample code supplied allows an external controller to take full control of motors and servos as well as reading the voltage current and 3 axis acceleration sensors The default I C slave address is 0x07 7 decimal however this can be changed through the I2C interface with the new address being stored in the EEPROM so it will not be lost when power is disconnected The default clock speed is 100kHz but is software selectable between 100kHz and 400kHz Servos The TREX controller can drive up to 4 servos at 6V in high voltage mode or battery voltage 6V 7 4V in low voltage mode An additional 2 servos can be powered at 5V if encoders are not being used Bluetooth The PREX controller allows a DAGU blue tooth module to plug directly into the controller so that it can be controlled by a mobile phone This allows customers to write mobile phone apps that combine the mobile phone s
14. sample code Heat Dissipation Heat generation is minimised by using FET s with a much higher current rating than required This also allows the controller to handle short term overloads without damage The 4 layer PCB uses the 2 middle layers to conduct heat throughout the PCB making the entire PCB into one large heat sink If total current draw from the battery exceeds 20A continuous then a heatsink or small fan will be required Low Voltage Mode Use low voltage mode when using low voltage batteries such as 6V SLA 7 2V NiMh and 7 4V LiPo batteries Short the pins on the LV mode jumper to bypass the switch mode regulator and V SERVO 5V GND power both servos and the SV regulator directly ow Voltage from the battery Mode Select Power Out The 5V regulator will get much hotter in this mode so the 5V current should be limited to 800mA unless a heatsink and fan are added directly to the LM1084 regulator IC High Voltage Mode When using batteries with a nominal voltage higher than 8V leave the LV mode jumper pins disconnected The switch mode regulator efficiently reduces battery voltage to 6V for powering servos and the 5V regulator In this mode the maximum current for servos and the 5V regulator combined is 3A The 5V regulator can deliver 2A for powering external controllers such as the Raspberry Pi Beagle Bone or other Arduino controllers Dual H Bridges The H bridges power motors directly from the battery and allow s
15. y the motor in mA Encoder count Optional encoders can be attached to D5 right and D6 left When the motor speed is positive the encoder counter will increment every time the input changes state If the speed is negative then the counter will decrement when the input changes state Engaging the left brake with the left speed set to 0 will reset the left counter Engaging the right brake with the right speed set to 0 will reset the right counter Accelerometer readings This is the raw data from the accelerometer and can be used to determine the angle and acceleration of the robot Impact readings The sample code reads the accelerometer every 2mS and compares the old readings to the new readings A significant change in values indicates an impact has occurred When an impact is detected the relative change in the X Y and Z axes are given and further impact detection is disabled for 100mS to prevent false triggering from chassis vibration Values of 0 indicate no impact has been detected Sensitivity and de vibrate settings can be adjusted in the command data packet T REX Robot Controller Specifications Processor MCU Clock speed Logic voltage FLASH SRAM EEPROM Bootloader Power supply Supply voltage Power switching FET maximum current Switch mode regulator 5V output current Dual H bridge Voltage Current per motor Current sensor Fuse type Fuse resistance Fuse hold current 23 C
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