Chimera/v1.00

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Overview

• STMicro STM32F767 Micro Controller Unit
  • ARM Cortex-M7, 216 MHz CPU, FPU & DSP instructions, 2 Mbytes Flash, 512 Kbytes SRAM, General-purpose DMA,etc.
  • Unlike STM32F4, FPU of STM32F767 double precision capable. It means double precision computation is 10 times faster on chimera than on STM32F4 based hardware
• 9 DOF Inertial Measurement Unit
• Barometer/altimeter (I2C, IMU slave capability)
• Differential Pressure Sensor for Pitot tube
• microSD card (+ dedicated power supply for emergency files closing system)
• All connectors available both in standard 0.1” header and Molex Picoblade (except servos and R/C receiver, 0.1” header only)
• Dedicated serial link and power supply for "Companion Computer" (Beaglebone, Raspberry, Gumstix, ...)
• x4 status Leds + 8 segments LED display
• SWD debug connector (STM STLink compliant header)
• x8 Servos (+ Servos Power supply selection capabilities: Chimera onboard power supply or external source)
• x2 RC Receiver inputs (S.BUS, PPM & Spektrum Satellite compatible, including receiver binding)
• x5 UARTs (including one with hardware flow control signals)
• x1 I2C bus (3.3V and 5V logic level)
• x1 SPI bus (with Slave Select, Master or Slave)
• x1 CAN bus
• x8 auxiliary Inputs/Outputs spread over 2 connectors (x6 ADC, x6 Timers different from servos, x1 UART, x1 DAC)
• XBEE modem holder (ASSO and Reset connected to MCU GPIOs)
• x1 USB :
  • DFU mode (download) or USB storage (direct access to MicroSD card)
  • micro-USB plug (+ Picoblade & 0.1” header in //)
  • Board can be flashed even if aircraft battery is off)
• Controlled Powerswitch 5V supply on AUX A (AUX0 to 3) header
• Twin switching power supply :
  • source 2 to 6 Lipo cells (6 to 26v)
  • 5v/3A for “Companion” Computer(controlled by GPIO)
  • 5v/3A dedicated to Chimera (servos and other 5v peripherals)
• VBat+Gnd connectors for peripheral
• 89x60mm (3.5x2.4")

Hardware Revision History

Version #	Release Date	Release Notes
v1.00	10/2016	Initial release of Chimera

Pictures

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Detailed Features

MicroSD card (SDIO)

• software support available with v5.2 and above
• hi-cap power designed to give enough time to cleanly save buffer and close file(s) when power outage detected
• USB-storage mode when plugging an USB cable after startup

On-board Sensors

• 9 DOF IMU
  Invensense chip MPU-9250 : 9 DOF, 3 axis Accelerometer + 3 axis Gyroscope + 3 axis Magnetometer
• Barometer/Altimeter
  TE Connectivity module MS5611-01BA03 : High resolution Integrated digital pressure sensor, 10 to 1200 mbar, 24 bit ADC, I2C & SPI interface
• Differential pressure sensor / Pitot
  TE Connectivity transducer MS4525DO-DS5AI001DP : Digital Output Temperature and Differential Pressure sensor, Dual Sideport, 1PSI pressure range, I2C interface

USB Modes

• USB plugged before autopilot is powered : enter DFU mode to be flashed
  New ! : Can be flashed even if autopilot is not powered.
• USB plugged after autopilot is powered : stop ap task, enter usb storage mode to made sdcard content easily avalaible, after the host has mounted;copied;dismounted storage;unplugged usb, ap restart

SWD: Serial Wire Debug

Permits flash and source level debugging via SWD part of cheap discovery card, or via more capable, fastest, more expensive probe like black magic probe or CricketProbe

R/C Serial

Chimera offer two different R/C Receiver port allowing direct connection (3 pin) of several brand off-the-shelf receivers without hardware modification or external encoder board:

• RC1: PPM (Timer2 or 5 / Ch2) or S.BUS (inverted UART4 Rx) or Serial (non-inverted UART4 Rx) or Serial Spektrum satellite (non-inverted UART4 Rx + GPIO for binding procedure)
• RC2: S.BUS (inverted UART7 Rx) or Serial (non-inverted UART7 Rx) or Serial Spektrum satellite (non-inverted UART4 Rx + GPIO for binding procedure)

(see R/C Receivers and Radios page for compatible receivers)

Power

The input power source (Battery) voltage range of Chimera is 6V to 26V (2 to 6 Lipo cells)

• Twin Power Supply
  • one 5V/3A dedicated to Chimera, servos (see Servo Power Supply selection below) and other 5V peripheral
  • one 5V/3A dedicated to "Companion Computer" available on UART1 connector ("5V Comp.",#2) can be switched ON and OFF on demand using EN_COMP (MCU GPIO output PC04).
    • EN_COMP = 1 => 5V Comp. OFF
    • EN_COMP = 0 => 5V Comp. ON (default)

• Servo Power Supply selection
  Chimera offer 2 options for servo power supply
  • Onboard 5V, provided total current (autopilot + external 5V modules + servos) does not exceed 3A.
  • External 5V source (BEC) for special servo configuration

(see Servo Power options section below for more information)

• Power Switch
  5V power output pin on AUX A connector ("5V Aux.",#2) can be switched ON and OFF on demand using APSW (MCU GPIO output PE06).
  • APSW = 0 => 5V Aux OFF
  • APSW = 1 => 5V Aux ON (default)

The internal switch TPS2051B is designed to withstand 500mA continuous current and is short-circuit and thermally protected.
(see TPS2051B datasheet for recommended operation conditions)

Onboard Modem

Chimera offer two options for Modem:

• External Modem.
  In this case, Modem should be plugged on "UART3" serial interface connector.
• Onboard XBee module.
  In this case, XBee pins are connected to :
  • Dout -> UART3 Rx (PD09)
  • Din -> UART3 Tx (PD08)
  • Asso -> GPIO (PA08)
  • Reset -> GPIO (PE15)
    Note : do not use UART3 Rx and Tx signals if XBee plugged.

Companion Computer

Chimera allows to easily connect a "Companion Computer" (Raspberry Pi, BeagleBoneBlack, Intel Edison, Odroid, etc.) to perform on-board computationally intensive tasks impossible to achieve by the autopilot alone.
This connection is made using "UART1" connector which offer:

• Dedicated 5V/3A supply (can be switched ON and OFF on demand using EN_COMP, GPIO output PC04)
• Serial interface UART1 Rx (PB07) & Tx (PB06) for fast communication

Communication Buses

• UART/Serial
  5 UART serial communication:
  • x1 with hardware flow control signals (UART 2)
  • x1 for GPS receiver (UART 8)
  • x1 (free if no) modem XBee (UART 3)
  • x1 (free if no) “Companion Computer” (UART 1)
  • x1 free on AUX B connector (UART 6)

• I2C Bus
  I2C2 interface (SDA2-PB11 and SCL2-PB10) is available in two voltage levels to allow connection of various types of external sensors:
  • 3.3V Logic ("I2C2 3V3" 2x 0.1" header and 2x Molex Picoblade connectors in //)
  • 5V Logic ("I2C2 5V" 1x 0.1" header and 1x Molex Picoblade connectors in //)

Note: for testing purpose, I2C1 internal bus signals dedicated to IMU and IMU Slave I2C Bus dedicated to Barometer and Differential pressure sensor are available on 4 pads (or 4 pin MolexPicoblade connector if populated) next to the IMU.

• SPI Bus
  SPI1 interface (MOSI1-PB5 MISO1-PB4 SCK1-PB3 NSS1-PA15) is available on "SPI1" connector.
  If more than one selection signal (NSS1) is needed, use auxiliary pins (AUX0 to AUX7) configured as GPIO output

• CAN Bus

LEDs & Display

• 4x Leds classical paparazzi state diplay
• 1x 7 segment (plus dot) Led digit for extended mode display

Pinout

Pins Name and Type are specified with respect to the Autopilot Board

General Pinout

UART1 (Companion)

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V Comp.	PWR	Controlled by PC5	5V/3A specific for Companion Computer (PC5 = LOW => ON (default, pulldown) / PC5 = High => OFF)
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	RX1	IN	PB7	UART1 Serial Input (3.3V level, 5V tolerant)
5	TX1	OUT	PB6	UART1 Serial Output (3.3V level)

UART2

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	RX2	IN	PD6	UART2 Serial Input (3.3V level, 5V tolerant)
5	TX2	OUT	PD5	UART2 Serial Output (3.3V level)
6	RTS2	OUT	PD4	UART2 Flow Control Request to Send (3.3V level)
7	CTS2	IN	PD3	UART2 Flow Control Clear to Send (3.3V level, 5V tolerant)

UART3 (Modem)

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	RX3	IN	PD9	UART3 Serial Input (3.3V level, 5V tolerant) DO NOT USE if XBee module present on Chimera
5	TX3	OUT	PD8	UART3 Serial Output (3.3V level) DO NOT USE if XBee module present on Chimera

UART8 (GPS Receiver)

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	RX8	IN	PE0	UART8 Serial Input (3.3V level, 5V tolerant)
5	TX8	OUT	PE1	UART8 Serial Output (3.3V level)

I2C2 (3V3)

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	SDA2	Open Drain I/O	PB11	I2C2 bus Serial DAta (3.3V level, 1.5k pull-up)
5	SCL2	Open Drain I/O	PB10	I2C12 bus Serial CLock (3.3V level, 1.5k pull-up)

Note: 2 x Molex Picoblade and 2 x 0.1" Header are all in parallel

I2C2 (5V)

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	SDA2	Open Drain I/O	PB11	I2C2 bus Serial DAta (5V level, 3.3k pull-up)
5	SCL2	Open Drain I/O	PB10	I2C12 bus Serial CLock (5V level, 3.3k pull-up)

SPI1

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	NSS1	OUT	PA15	Slave Select. Selects the SPI slave
5	MOSI1	I/O	PB5	SPI1 Master Out Slave In. Data output from master / data input to slave
6	MISO1	I/O	PB4	SPI1 Master In Slave Out. Data input to master / data output from slave
7	SCK1	I/O	PB3	SPI1 Serial clock. Clock output from master or input to slave

AUX A (paparazzi names)

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V Aux	PWR	Controlled by PC4	5V from autopilot through Power Switch (PC4 = LOW => OFF / PC4 = High => ON)
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	AUX1	I/O	PA5	General Purpose I/O (LED 5, SPI SLAVE1) / ADC1+2 in5 (ADC_1) / DAC2 / TIM2 ch1
5	AUX2	I/O	PA3	General Purpose I/O (LED 6, SPI SLAVE2) / ADC1+2+3 in3 (ADC_2) / TIM2 ch4 / TIM5 ch4 / TIM9 ch2
6	AUX3	I/O	PA2	General Purpose I/O (LED 7, SPI SLAVE3) / ADC1+2+3 in2 (ADC_3) / TIM2 ch3 / TIM5 ch3 / TIM9 ch1
7	AUX4	I/O	PA0	General Purpose I/O (LED 8, SPI SLAVE4) / ADC1+2+3 in0 (ADC_4) / TIM2 ch1 (PWM_INPUT1) / TIM5 ch1

AUX B (paparazzi names)

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	+3.3V	PWR	-	3.3V Rail from autopilot
4	AUX5	I/O	PC3	General Purpose I/O (LED 9, SPI SLAVE5) / ADC1+2+3 in13 (ADC_5)
5	AUX6	I/O	PC2	General Purpose I/O (LED 10) / ADC1+2+3 in12 (ADC_6)
6	AUX7	I/O	PC6	General Purpose I/O (LED 11) / TIM3 ch1 / TIM8 ch1 / UART6 Tx
7	AUX8	I/O	PC7	General Purpose I/O (LED 12) / TIM3 ch2 / TIM8 ch2 (PWM_INPUT2) / UART6 Rx

CAN

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	CANH	I/O	-	CAN bidirectional + line
4	CANL	I/O	-	CAN bidirectional - line

Note: Embedded 120R terminator resistor.

USB

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	USB+	I/O	PA12	USB bidirectional D+ line
3	USB-	I/O	PA11	USB bidirectional D- line
4	VBUS	IN	PA9	Indicates the presence of USB bus power (5V level), DFU or USB storage Mode selection (BOOT0 MCU pin)

Note: MicroUSB, Molex Picoblade and 0.1" Header USB connectors are in parallel, only one can be connected at a time.

SWD (Serial Wire debug)

Pin #	Name	Type	MCU Port	Description
1	+3.3V	PWR	-	3.3V Rail from autopilot
2	SWCLK	IN	PA14	SWD Serial Clock
3	GND	PWR	-	common ground
4	SWDIO	I/O	PA13	SWD Serial Data
5	RST	IN	NRST	MCU Reset
6	NC	-	-	Not connected, for STM ST-LINK/V2 connector compliance

Note: Pin to pin compatible with STM ST-LINK/V2 debug tool connector

Power Out

Pin #	Name	Type	Description
1	GND	PWR	common ground use only to power peripheral modules, DO NOT use as power supply input for autopilot
2	VBAT	PWR	+ Rail from battery use only to power peripheral modules, DO NOT use as power supply input for autopilot

R/C Receivers and Servos header pinout

RC Receiver 1

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	RC1	I/O	PA1	Serial (SBUS, Spektrum, etc.) or PPM Stream RC receiver signal (5V Tolerant) UART4 Rx / TIM2 ch2 / TIM5 ch2 PPM, SPEKTRUM primary, SBUS secondary

RC Receiver 2

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V	PWR	-	5V Rail from autopilot
3	RC2	I/0	PE7	Serial (SBUS, Spektrum, etc.) RC receiver signal (5V Tolerant) UART7 Rx SBUS primary, SPEKTRUM secondary

Servo 0/1/2/3/4/5/6/7

Pin #	Name	Type	MCU Port	Description
1	GND	PWR	-	common ground
2	+5V Servo	PWR	-	5V Rail for Servos
3	SRV0 SRV1 SRV2 SRV3 SRV4 SRV5 SRV6 SRV7	OUT	PA6 PA7 PB0 PB1 PD12 PD13 PD14 PD15	Servo signal (PWM)

Servo Power options

There is two options to supply connected servos.
Note : Whatever option is chosen, autopilot's ground already connected to servomotor's ground.

Powering Servos with Autopilot

This option can be used provided total current from 5V rail (autopilot + external 5V modules + servos) does not exceed 3A.
In this case, 5V servo rail must be connected to autopilot 5V rail as described below.

Warning: make sure shunt current rating exceed servos total consumption
A practical way of making this connection is to use a 2 or 3 way shunt like Samtec's MNT-103-BK-G (3.9A/pin)

Powering Servos using an external BEC/Power Source

This option must be used if total current from 5V rail may exceed 3A or for other special servo configuration.

Schematic

Board production

Gerber & Drill for PCB

PCB design Eurocircuits 6-C class compliant:

Download Chimera v1.00 PCB production files (zip)

RS274X, units = Inches, format = 2:5

• Chimera_v100_Silkscreen_TOP.GBR (Top Component Print Layer)
• Chimera_v100_Soldermask_Top.GBR (Top Solder Mask)
• Chimera_v100_Paste_Mask_Top.GBR (Top Paste Mask, stencil)
• Chimera_v100_Signal_Top.GBR (Top Copper Layer)
• Chimera_v100_Internal_Plane_1.GBR (Internal Copper Layer GND)
• Chimera_v100_Internal_Plane_2.GBR (Internal Copper Layer +3.3V)
• Chimera_v100_Signal_Bottom.GBR (Bottom Copper Layer)
• Chimera_v100_Soldermask_Bottom.GBR (Bottom Solder Mask)
• Chimera_v100_Outline.GBR (Board Outline)
• Chimera_v100_Drill.GBR (NC XY coordinates & Drill tools sizes)

Bill Of Material

Download Chimera v1.00 Bill of Material (zipped LibreOffice Calc & PDF file)

Components Layout

• 

  Chimera v1.00 components Layout
  (no Xbee modem & no differential pressure sensor)

• 

  Chimera v1.00 components Layout

• 

  Chimera v1.00 components detail

Pick-and-Place

Download Chimera v1.00 Pick-and-Place files (zip)

• Chimera_v100_pick_place.csv
• Chimera_v100_pick_place.pik
• Chimera_v100_pick_place.txt

Mechanical Dimensions

Programming

In order to compile airborne code for the STM32F7 line, it is required to have a GCC 5.4.x or above. If not packaged by default in your distribution, you need to download and install it from https://launchpad.net/gcc-arm-embedded.

Chimera autopilot can reprogrammed in two different ways:

• Using the MCU native (embedded in rom) DFU USB bootloader over the on-board USB connectors (so pre-loading an "external" bootloader is useless)
  • required hardware : USB cable with USB-micro connector
  • required software : dfu_util tool (present in ubuntu repository)
• Using the SWD (Serial Wire Debug) connector
  • required hardware : SWD part of a cheap stm32 evaluation board (any discovery board, start @ 8$), 2.54mm pitch pin-to-pin cable and USB cable with USB-mini or micro connector matching your evaluation board
  • required software : st_flash and st_util, have to be compiled from source (https://github.com/texane/stlink)

On-board Data Logging

It is possible to write data on the embedded SD card from the main autopilot program. In order to cope with a real-time constraints of the autopilot, a light RTOS called ChibiOS is used to split the logging task from the rest of the system. Two modules are necessary to enable the logging system: the driver of the SD card system that also handle the file system (using FATFS) and a dynamic memory allocation system called TLSF. In order to enable this features for your Chimera board, you need to select the correct board type and add the required modules to the firmware section of your airframe file (logging is currently only available for fixedwing firmware):

<firmware name="firmware">
 ...
 <target name="ap" board="chimera_1.0">
   ...
 </target>
 ...
 <module name="tlsf"/>
 <module name="logger" type='sd_chibios"/>
</firmware>

This will active the automatic opening of a new log file (30 seconds) after each startup of the autopilot. Then you can freely write ASCII or binary data into this file (see a simple example logging for meteorological data logging). The file is automatically closed upon battery disconnection, no need to press any button to stop the logging.

To recover the data on the SD card, just power up the board without the USB plugged (otherwise it will enter in DFU boot mode), then plug the USB cable to the board and to your computer. This will stop the main autopilot program and will mount the SD card as a regular mass storage with a FAT file system. The log files are placed in a PPRZ folder. Unplugging the USB will reset the autopilot.

In addition to this, you can also load a flight recorder module (it also needs the pprzlog module for supporting the specific paparazzi binary log format).

<firmware>
 ...
 <module name="pprzlog"/>
 <module name="flight_recorder"/>
 ...
</firmware>

with the appropriate telemetry file (conf/telemetry/fixedwing_flight_recorder.xml). This will automatically open a second file where telemetry messages described in the FlightRecorder section of the telemetry file will be logged in binary format. The files are store in a separated FR folder on the SD card. The decoding procedure is the same than OpenLog and is using the sd2log tool:

~/paparazzi/sw/logalizer/sd2log [log_file] [optinal_output_dir]

This will produce 3 files: a .log and a .data files similar to the normal ground station log and .tlm file that is a simple copy of the binary file (but rename with the same base name than the two others).

Debugging

Debugging with STM Discovery ST-LINK/V2 embedded debug tool

Debugging with CricketProbe

Source code

Available in latest git master branch.

Where to Buy

Check availability on Get Hardware page