Bottom board schematic

The table below contains schematics, PCB layouts and element placement (PCB views are in 4:1 scale).

Name File
Bottom board schematic bottom_sch
Bottom board PCB (top layer) bottomTop_brd
Bottom board PCB (bottom layer, mirrored) bottomBottom_brd
Bottom board PCB elements layout (top layer) bottomTop_doku
Bottom board PCB elements layout (bottom layer, mirrored) bottomBottom_doku
Bill of materials bom
Eagle v6 project files zip


The bottom board consists of three main modules: Motors, Power Supply and Connectors. The first module consists of two Freescale Semiconductors MC33926 motor controllers (H bridges), which are responsible for control of eye protrusion. Communication between the MCU and each of these IC's is carried out with 6 signals:

  • ~D2 – disable input 2 (active low)
  • IN1 – input control of OUT1
  • IN2 – input control of OUT2
  • EN – circuit enable
  • ~SF – status flag (active low)
  • FB – load current feedback

In case of EMYS head controller, combination of IN1 and IN2 controls motor direction, whereas ~D2, connected to PWM signal from MCU, controls movement speed. Outputs of the H bridges are connected to X13 (left translation motor, joint q8), and X14 (right translation motor, joint q11).


X13, X14 connectors
 Pin  Signal Description
1 M+ Eye protrusion motor +
2 M-  Eye protrusion motor -


Power Supply module consists of three sections – Servo power supply, Logic power supply and Power LEDs. The first one consists of a 5A, 2,5 MHz (operating at 600 kHz), monolithic, synchronous step-down regulator TPS54560, which provides power supply of 4V5 for four eye servomotors (eyebrows and eyelids). Logic power supply utilizes dual, 700mA, 2,2 MHz (operating at 700 kHz),  step-down regulator LT3509 for providing 3V3 and 5V power supply. The 3V3 is supplied to the MCU and differential decoder for eye protrusion motor encoders, whereas 5V is supplied to the communication circuit and RGB camera. Power LEDs indicate presence of input power supply (10-14V8) and servo power supply (4V5).

Connectors module consists of four sections – Servos, Board-to-board, Encoders and Main connector. Servos section contains four servo connectors: X5 (right eyelid, joint q9), X6 (right eye rotation, joint q10), X7 (left eyelid, joint q6), X8 (left eye rotation, joint q7) (sides are given from the perspective of the robot, not the user). Each servo has an independent current measurement circuit based on ZXCT1109 integrated circuit.


X5-X8 connectors
 Pin  Signal Description
1 GND Ground
2 VCC 4V5 power supply connected via sensing shunt resistor
3 PWM PWM control signal from the MCU connected via a 100 ohm resistor


Main connector section consists of two 4-pin Molex micro spox connectors X9 and X10, used in Robotis Dynamixel servomotors and compatible with their pinout. One connector is used for connecting the head controller to the motors below the middle disk, the other one for connecting the top disc servo to the bus.


X9, X10 connectors
 Pin  Signal Description
1 RS485_A RS485 A+ signal
2 RS485_B RS485 B- signal
3 V+ Power supply from 10V to 14V8 (12V recommended)
4 GND Ground


Encoders section contains two eye protrusion motor encoders connectors – X11 (left motor encoder) and X12 (right motor encoder) (sides are given from the perspective of the robot, not the user), compatible with maxon motor standard.


X11, X12 connectors
 Pin  Signal Description
1 NC Not connected
2 +5V 5V power supply
3 GND Ground
4 NC Not connected
5 MOT_ENC_\A Channel A complement
6 MOT_ENC_A Channel A
7 MOT_ENC_\B Channel B complement
8 MOT_ENC_B Channel B
9 NC Not connected
10 NC Not connected


Section board to board consist of four micro-match connectors: X1(right connector), X2 (back connector), X3 (left connector) and X4 (front connector), transferring signals between top and bottom board.


X1 connector
 Pin  Signal Description
1 PTB8_MOTR_IN2 Right motor IN2
2 PTB9_MOTR_IN1 Right motor IN1
3 ADC1_SE4_MOTR_FB Right motor feedback
4 PTB10_MOTR_EN Right motor enable
5 FTM0_CH0_MOTR_~D2A Right motor IN2 enable (speed control using PWM)
6 PTB11_MOTR_~SF Right motor fault signal
7 GND Ground
8 +5V 5V power supply (for communication ICs and camera)


X2 connector
 Pin  Signal Description
1 MOT_R_ENC_\A Right motor channel A complement
2 MOT_R_ENC_A Right motor channel A
3 MOT_R_ENC_B Right motor channel B
4 MOT_R_ENC_\B Right motor channel B complement
5 MOT_L_ENC_\A Left motor channel A complement
6 MOT_L_ENC_A Left motor channel A
7 MOT_L_ENC_B Left motor channel B
8 MOT_L_ENC_\B Left motor channel B complement


X3 connector
 Pin  Signal Description
1 +3V3 3V3 power supply (for MCU and differential decoder)
2 GND Ground
3 PTE0_MOTL_IN2 Left motor IN2
4 PTE1_MOTL_IN1 Left motor IN1
5 ADC1_SE5_MOTL_FB Left motor feedback
6 PTE2_MOTL_EN Left motor enable
7 FTM0_CH1_MOTL_~D2 Left motor IN2 enable (speed control using PWM)
8 PTE3_MOTL_~SF Left motor fault signal


X4 connector
 Pin  Signal Description
1 ADC1_DM0_SERVO Current measurement from left eye rotation servo
2 ADC1_DP0_SERVO Current measurement from left eyelid servo
3 FTM0_CH7_SERVO PWM control signal for left eyelid servo
4 FTM0_CH6_SERVO PWM control signal for left eye rotation servo
5 RS485_B RS485 B- signal
6 RS485_A RS485 A+ signal
7 FTM0_CH5_SERVO PWM control signal for right eye rotation servo
8 FTM0_CH4_SERVO PWM control signal for right eyelid servo
9 ADC0_DM0_SERVO Current measurement form right eye rotation servo
10 ADC0_DP0_SERVO Current measurement form right eyelid servo


Top board schematic

The table below contains schematics, PCB layouts and element placement (PCB views are in 4:1 scale).


Name File
Top board schematic top_sch
Top board PCB (top layer) topTop_brd
Top board PCB (bottom layer, mirrored) topBottom_brd
Top board PCB elements layout (top layer) topTop_doku
Top board PCB elements layout (bottom layer, mirrored) topBottom_doku
Bill of materials bom
Eagle v6 project files zip


Top board consists of the following modules: Microcontroller, Communication, Encoders, Misc and Connectors. The first one contains Freescale Semiconductors MK40DN512VLK10 microcontroller from Kinetis K40 family. To get more information about this particular MCU check out its documentation LINK LINK.

Communication module consists of the  following sections: USB-RS485 PC, RS485 K40 and Hub USB. The first section contains FT232RQ integrated circuit which is responsible for USB to UART conversion. The output of FT232RQ is connected to SN65HVD485EDGK, which converts it to RS485. This signal goes to RS485 bus, which controls all EMYS' drives. RS485 K40 utilizes the same IC - SN65HVD485EDGK to convert the RS485 signal to UART signal, which is connected to the MCU. Hub USB is based on FE1.1s IC with four inputs, of which three are in use - USB_CAMERA (signal from the camera built into EMYS’ nose), USB_SERVOS (RS485 bus controlling the EMYS motors, after conversion to USB signal) and USB_K40 (signal from K40 MCU, used for debug purposes).

Encoders module utilizes low-voltage, high-speed quadruple differential line receiver AM26LV32E for conversion from differential to single-ended encoder signals, which are connected to K40 quadrature decoders.

Misc module consist of four sections: Limit switches (for eye protrusion), Signal LEDs (error, Tx and Rx indicators), Clock (8MHz oscillator) and MCU_Filters with capacitors and filters required for proper MCU operation.

Connectors module consists of six sections: Board-to-Board, TSI, J-Link, USB, Camera and Battery. The first one contains X1, X2, X3 and X4 Micro-Match connectors for connecting both boards together. Its pinout is the same as in the bottom board. TSI contains X5, a 5-pin Molex PicoBlade connector for 5 signals from the touch sensing electrodes. J-link section contains X6, J-link needle adapter, which enables programming of the board. USB contains X7, a 4-pin Molex PicoBlade connector for the main USB signal, which is connected to the upstream port of the USB Hub. Camera contains X8, a 4-pin Molex PicoBlade connector for camera USB, connected to the downstream port of the USB Hub.


X4 connector
 Pin  Signal Description
1 TSI0_CH7 Upper disk touch sensor 
2 TSI0_CH8 Middle disk left touch sensor 
3 TSI0_CH9 Middle disk front touch sensor 
4 TSI0_CH10 Middle disk right touch sensor 
5 TSI0_CH13 Lower disk touch sensor 


X6 J-link needle adapter
 Pin  Signal Description
1 VTref +3V3 power supply
3 GND Ground
5 5V-Supply Not connected
7 RTCK Not connected
8 TDI JTAG_TDI signal
9 TRST Not connected
10 nRESET RESET signal


X7 connector
 Pin  Signal Description
1 +5V Not connected
2 DM USB_DM_COMP (through 33 om)
3 DP USB_DP_COMP (through 33 om)
4 SWCLK/TCK GND (through filter)


X8 connector
 Pin  Signal Description
1 +5V 5V power supply



EMYS and FLASH are Open Source and distributed according to the GPL v2.0 © Rev. 1.0, 04.04.2018

FLASH Documentation