Headers & Signals

In BigClown we emphasize hardware modularity and re-usability. To achieve such goal we had to come up with proper interconnect system between our components. We decided to stick with well-known and widely accepted standard - headers with 2.54 mm (0.1 inch) pitch.

Our header system consists of two types of components - pins and sockets.

In order to maintain compatibility between various hardware components we came up with our own two standards for electro-mechanical format - module and tag.

Module Format

Format Module defines:

  • Spacing and signals between two rows of 14-pin headers.
  • Four mounting hole positions and their diameter.
  • Position of mechanical key (filled hole in header) preventing reverse insertion.
  • Position of sockets from top view.
  • Position of pins from the bottom view.
  • Recommended PCB height is 55 mm.
  • Recommended PCB thickness 1.5 mm.
  • Radius of rounded corners 3.8 mm.

Module Drawing

Module Signals

This is a summary of basic peripherals available on module header:

  • 18x GPIO channels (General Purpose Input/Output)
  • 5x ADC channels (Analog-to-Digital Converter)
  • 2x DAC channels (Digital-to-Analog Converter)
  • 3x UART channels (Universal Asynchronous Receiver Transmitter)
  • 2x I²C bus (Inter-Integrated Circuit)
  • 1x SPI bus (Serial Peripheral Interface)

The following table defines signal assignment on module header:

Signal Description
1 P0 GPIO channel 0
A0 ADC channel 0
TXD0 UART channel 0 - TXD signal
2 P1 GPIO channel 1
A1 ADC channel 1
RXD0 UART channel 0 - RXD signal
3 P2 GPIO channel 2
A2 ADC channel 2
TXD1 UART channel 1 - TXD signal
4 P3 GPIO channel 3
A3 ADC channel 3
RXD1 UART channel 1 - RXD signal
5 P4 GPIO channel 4
A4 ADC channel 4
DAC0 DAC channel 0
6 P5 GPIO channel 5
A5 ADC channel 5
DAC1 DAC channel 1
7 P6 GPIO channel 6
RTS1 UART channel 1 - RTS signal
8 P7 GPIO channel 7
CTS1 UART channel 1 - CTS signal
9 P8 GPIO channel 8
10 P9 GPIO channel 9
11 RESET System reset
Also button "R" on Core Module
12 BOOT Boot mode
Also button "B" on Core Module
13 VDD_OFF From top side: VDD_OFF output
From bottom side: VDD_OFF input
14 BAT_OFF Battery disconnect signal
15 GND System GND (ground)
16 VDD System VDD (positive rail)
17 SCL0 I²C bus 0 - SCL signal
18 SDA0 I²C bus 0 - SDA signal
19 INT System interrupt signal
20 System interrupt signal
21 P10/RXD2 UART channel 2 - RXD signal
22 P11/TXD2 UART channel 2 - TXD signal
23 P12/MISO SPI bus - MISO signal
24 P13/MOSI SPI bus - MOSI signal
25 P14/SCLK SPI bus - SCLK signal
26 P15/CS SPI bus - CS signal
27 P16/SCL1 I²C bus 1 - SCL signal
28 P17/SDA1 I²C bus 1 - SDA signal

Tag Format

The primary purpose of tag format is to provide signal break-out for I²C peripheral in a compact form-factor. It can be anything I²C-related - e.g. sensors, memories, RTCs, etc.

Format tag defines:

  • Signals on a 5-pin header.
  • Letter "D"-shaped PCB outline.
  • Mechanical dimensions 16 x 16 mm.
  • Recommended PCB thickness 1.5 mm.
  • Radius of rounded corners is 3.8 mm.

Tag Drawing

Tag Signals

The following table defines signal assignment on tag header:

Signal Description
1 GND System GND (ground)
2 VDD System VDD (positive rail)
3 SCL I²C bus - SCL signal
4 SDA I²C bus - SDA signal
5 INT System interrupt signal

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