Phobos v1.1

This sheet shows the documentation for the Phobos board.


The Phobos board is a certified PCB that allows to create electronics devices using exclusively standard modules. It combines the ease-of-use standard modules with a reduced form factor PCB. It has been developed for the Internet of Things (IoT) bearing in mind the fast product development. The board includes also a battery management circuit bringing to the designer the capacity to made portable devices.

The next figures show a 3D view for the Phobos board.

Phobo11 3D Top v2.png Phobos11 3D Bottom v1.png

As a summary, the following table indicates the main features:

Phobos features
USB 1 USB type B
Expansion headers 44 pin modules 1x S200 Master Module slot
1x Slave Module slot


  • Internet of Things
  • Wearables
  • Makers
  • Fast prototyping
  • Trackers

Board specifications

The Phobos board has been designed for working only with modules, so a core is not needed. Two standard modules holders are available, one for the master module and another for the slave. That brings simplicity and speed up the product designing and development stage.

There are two different ways to empower the system: using the micro-USB connector or a battery. The PCB also includes a Lithium battery charge management controller bringing the capacity to work independently of the power supply.

As a summary, here are the key features for the Phobos board:

  • Capacity for holding two modules: master and slave
  • There is no need for a Core
  • Compatibility with all the modules
  • Fast prototyping
  • USB connector for data and power supply
  • In-circuit battery management
  • Small form factor

The block diagram shows the parts that make it possible.

Phobos11 Block Diagram v2.png

The following figure identify the main parts of the board. The most important parts will be explained with more details in the next sections.

Phobos11 Description Top v1.png Phobos11 Description Bottom v1.png Core

The Phobos board has no core sockets. modules

Lots of modules focused in different areas such as communications, sensing or storage, are available. The Phobos board allows to connect one master module and one slave module. Look at here here to choose the desired module to convert your Phobos in the device you want.


Only one memory option is available in the Phobos board: a Memory eMMCXX Module.



There is available one USB 2.0 port on the Phobos board and it work as a host for the master module. It is also three headers with a total of 44 pins that allow to access to some master module signals. The following table shows the pinout of the headers.

Pin Function
1 3V3
2 2V8
3 1V8
10 I2C-A_SCL
11 I2C-A_SDA
12 #NMI
13 GND
Pin Function
6 AD0
7 AD1
8 AD2
9 AD3 / DIFF-B_P
11 IO0
12 IO1
13 IO2
14 IO3
15 IO4
16 IO5
17 IO6
18 IO7
Pin Function
1 IO8
2 IO9
3 IO10
4 IO11
5 IO12
6 IO13
7 IO14
8 IO15
13 GND

Note: pin 9 of header H3 can be connected to AD3 signal from master module and to DIFF-B_P signal from slave module using 0R0 resistors. By default, the AD3 line is the closed one.

Phobos11 Wired Top v1.png


The Phobos board has nos wireless interfaces.


The Phobos board has no audio or video interfaces.

LEDs and Button

3 LEDs are assembled on the Phobos board in order to give status feedback to the user. The functionality is explained next:

  • Yellow LED: Turned on when the battery is being charging. Turned off when the battery is fully charged.
  • Green LED: Turned on when the battery is fully charged.
  • User LED: Programmable LED.

The Reset button is used to reset the microcontroller of the master module.

The User button is connected to #NMI signal of the master module and can be programmed as you want.

Phobos11 LEDsandButtons Top v1.png Phobos11 LEDsandButtons Bottom v1.png


S200 Master Module

The following table summarizes the standard signals of the master module socket and where they are used in the Helios board. These signals may have no functionality depending of the microcontrolled plugged on the board.

Pin Signal Used by Pin Signal Used by
2 SDIO-A_CMD Slave Module 49 QSPI_CS0 Slave Module
3 SDIO-A_CDN Slave Module 48 QSPI_IO3 Slave Module
4 SDIO-A_DATA3 Slave Module 47 QSPI_IO2 Slave Module
5 SDIO-A_DATA2 Slave Module 46 QSPI_CLK Slave Module
6 SDIO-A_CLK Slave Module 45 QSPI_IO1 Slave Module
7 SDIO-A_DATA1 Slave Module 44 QSPI_IO0 Slave Module
8 SDIO-A_DATA0 Slave Module 43 GND GND
9 GND GND 42 USB_N USB connector
10 - - 41 USB_P USB connector
11 - - 40 GND GND
12 - - 39 UART-B_RXD Slave Module, H3 pin 4
13 - - 38 UART-B_TXD Slave Module, H3 pin 3
14 - - 37 GND GND
15 - - 36 I2C-A_SDA Slave Module, H2 pin 11
16 - - 35 I2C-A_SCL Slave Module, H2 pin 10
17 GND GND 34 #NMI User button, H2 pin 12
18 VRTC Slave Module, H4 pin 10 33 GND GND
19 CLK32K Slave Module 32 SPI-A_MISO Slave Module, H2 pin 9
20 GND GND 31 SPI-A_MOSI Slave Module, H2 pin 8
21 CAN-A_RXD Slave Module 30 SPI-A_CLK Slave Module, H2 pin 7
22 CAN-A_TXD Slave Module 29 SPI-A_CS0 Slave Module, H2 pin 6
23 VBAT VBAT 28 INT0 Slave Module
24 27 GND GND
25 26 RESET_OUT Slave Module
Pin Signal Used by Pin Signal Used by
2 DIFF-A_N - 59 DIFF-A_P -
3 IO0 Slave Module, H3 pin 11 48 1WIRE Slave Module, ID EEPROM, H3 pin 5
4 IO1 Slave Module, H3 pin 12 47 VIO_OUT Slave Module, H4 pin 9
5 IO2 Slave Module, H3 pin 13 46 VIO_IN_MASTER -
6 IO3 Slave Module, H3 pin 14 45 GND GND
7 IO4 Slave Module, H3 pin 15 44 1V8 1V8
8 IO5 Slave Module, H3 pin 16 43 GND GND
9 IO6 Slave Module, H3 pin 17 42 - -
10 IO7 Slave Module, H3 pin 18 41 - -
11 - - 40 - -
12 GND GND 39 - -
13 UART-A_RTSN Slave Module 38 GND GND
14 UART-A_RXD Slave Module, H3 pin 2 37
15 UART-A_TXD Slave Module, H3 pin 1 36 2V8 2V8
16 UART-A_CTSN Slave Module 35
18 AD0 Slave Module, H3 pin 6 33
19 GND GND 32 3V3 3V3
20 PWM0 Slave Module, User LED 31
21 CAPT0 Slave Module 30 GND GND
22 CAPT1 Slave Module 29
24 27
25 26 #RESET_IN Reset button, H2 pin 4
Pin Signal Used by Pin Signal Used by
1 TS_XR - 50 AD5 -
2 TS_YD - 49 AD6 -
3 TS_XL - 48 COMP-A_P -
4 TS_YU - 47 COMP-A_N -
9 PWM4 - 42 UART-D_TXD -
10 OTG_P Slave Module 41 I2C-B_SDA -
11 OTG_N Slave Module 40 I2C-B_SCL -
12 OTG_ID USB connector 39 SPI-B_MOSI -
13 QSPI_CS1 - 38 SPI-B_MISO -
14 QSPI_CS2 - 37 SPI-B_SCK -
15 - - 36 SPI-B_CS0 -
16 - - 35 - -
17 - - 34 GND GND
18 - - 33 SPI-A_CS1 H2 pin 5
19 - - 32 SPI-A_CS2 -
20 - - 31 IO26 -
21 - - 30 IO27 -
22 - - 29 IO28 -
23 - - 28 PWM3 -
24 - - 27 PWM2 -
25 RS485_TXEN - 26 PWM1 -
Pin Signal Used by Pin Signal Used by
1 - - 50 IO8 H4 pin 1
2 - - 59 IO9 H4 pin 2
3 INT6 - 48 IO10 H4 pin 3
4 IN5 - 47 IO11 H4 pin 4
5 INT4 - 46 IO12 H4 pin 5
6 INT3 - 45 IO13 H4 pin 6
7 INT2 - 44 IO14 H4 pin 7
8 INT1 - 43 IO15 H4 pin 8
10 JTAG_TMS/SWDIO - 41 IO16 -
11 JTAG_TCK/SWCLK - 40 IO17 -
12 JTAG_TDO/SWO - 39 IO18 -
13 JTAG_TDI - 38 IO19 -
14 1V8 1V8 37 IO20 -
15 2V8 2V8 36 IO21 -
16 35 IO22 -
17 3V3 3V3 34 IO23 -
18 33 DAC0 -
19 32 DAC1 -
20 AREF1 - 31 - -
21 AREF0 - 30 GND GND
22 GND GND 29 AD1 H3 pin 7
23 COMP-B_P - 28 AD2 H3 pin 8
24 COMP-B_N - 27 AD3 H3 pin 9
25 AD13 - 26 AD4 -

For more details, look at the specifications for the standard.

Regarding the serial interfaces, three issues should be mentioned:

  • The USB data lines comes from the micro USB type B connector to the J201 master module connector.
  • For the I2C interface, the board provides two pull-up resistors (R10 and R11). Those pull-ups are defined as normally connected to the supply. If you want to disconnect the supply, there is a solder jumber next to the pull-up resistors.
  • Phobos board only has one slave module, so to get the most versatility, the UART-D has been replaced by UART-B in the slave module standar in order to be able to control a slave module with two UART interfaces with a S100 master module.


The Phobos board provides the needed voltages for the sockets. For doing so, Low Dropout Regulators (LDO) has been included for supplying the "1V8", "2V8" and "3V3" voltages. The "VSYS" voltage is switched in between "5V_USB" and "VBAT" (battery voltage) according to the following cases:

  • There is battery but the USB charger is not connected: VSYS = VBAT
  • There is battery and the USB charger is connected: VSYS = 5V (according to the USB standard)
  • There is no battery and the USB charger is connected: VSYS = 5V (according to the USB standard)
  • There is no battery and the USB charger is not connected: VSYS = 0V

As per the above, the Phobos board can work connected to a USB 5V source or with a battery. In this last case, only single cell Li-Po or Li-Ion batteries are supported. The charging current ranges from 15 to 500 mA. You can adjust it with potentiometer P1 following the next formula:

Ichrg(mA) = 1000V/(2k+P1)ohm

The "on/off" header allows you to turn off the system while the battery is still charging.

The following table summarizes the power supply signals on the Phobos board and indicates where are used.

Signal ( Voltage (V) Device
5V_USB 5 VSYS rail
VBAT VBAT VSYS rail, module, H4 pin 12
VSYS 3 - 5.5 modules, H4 pin 11
3V3 3.3 modules, H2 pin 1
2V8 2.8 modules, H2 pin 2
1V8 1.8 modules, H2 pin 3


Click the image below to download the schematic files.

Bill of materials

Click the image below to download the BOM files.

Fabrication files

Click the image below to download the fabrication files.

Mechanical specifications


Phobos11 Dimensions v1.png


  • Precaution against Electrostatic Discharge. When handling products, ensure that the environment is protected against static electricity. Follow the next recommendations:
  1. The users should wear anti-static clothing and use earth band when manipulating the device.
  2. All objects that come in direct contact with devices should be made of materials that do not produce static electricity that would cause damage.
  3. Equipment and work table must be earthed.
  4. Ionizer is recommended to remove electron charge.
  • Contamination. Be sure to use semiconductor products in the environment that may not be exposed to dust or dirt adhesion.
  • Temperature/Humidity. Semiconductor devices are sensitive to environment temperature and humidity. High temperature or humidity may deteriorate semiconductor devices characteristics. Therefore avoid storage or usage in such conditions.
  • Mechanical Shock. Care should be exercised not to apply excessive mechanical shock or force on the connectors and semiconductors devices.
  • Chemical. Do not expose semiconductor device to chemical because reaction to chemical may cause deterioration of device characteristics.
  • Light Protection. In case of non-EMC (Epoxy Molding Compound) package, do not expose semiconductor IC to strong light. It may cause devices malfunction. Some special products which utilize the light or have security function are excepted from this specification.
  • Radioactive, Cosmic and X-ray. Semiconductor devices can be influenced by radioactive, cosmic ray or X-ray. Radioactive, cosmic and X-ray may cause soft error during device operation. Therefore semiconductor devices must be shielded under environment that may be exposed to radioactive, cosmic ray or X-ray.
  • EMS (Electromagnetic Susceptibility). Note that semiconductor devices characteristics may be affected by strong electromagnetic waves or magnetic field during operation.

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