MicroMod mikroBUS™ Carrier Board Hookup Guide

Contributors: Santa Claus Impersonator, MAKIN-STUFF
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Hardware Overview

Board Dimensions

The MicroMod mikroBUS™ carrier board dimensions are approximately 3.35" x 1.40" with four mounting holes compatible with 4-40 screws or standoffs.

MicroMod mikroBUS carrier board dimensions
Dimensions of the MicroMod mikroBUS™ carrier board. (Click to enlarge)

The board also includes a mikroBUS™ socket for MikroElektronika's Click boards™.

Photo highlighting
mikroBUS™ socket to attach Click boards™. (Click to enlarge)

Common Components

Most SparkFun MicroMod Carrier Boards will have some common components and all MicroMod Carrier Boards will have the keyed M.2 MicroMod connector for a Processor board. The photo and list below outline the common components between the mikroBUS™ carrier board and other MicroMod Carrier Boards.

  • M.2 MicroMod Connector - This special keyed M.2 connector lets you install your MicroMod Processor of choice to the mikroBUS Carrier Board.
  • USB-C Connector - Connect to your computer to program your processor and provide power to the board.
  • 3.3V Regulator - Provides a regulated 3.3V and sources up to 1A.
  • Qwiic Connectors - The standard Qwiic connectors to connect other Qwiic devices for your MicroMod project.
  • Boot/Reset Buttons - Push buttons to enter boot mode on processors and to reset your MicroMod circuit.

Annotated photo for common components on the carrier board
Common MicroMod components featured on the MicroMod mikroBUS™ Carrier Board. (Click to enlarge)

Battery Charger

The board also has a MCP73831 Single-Cell Lithium-Ion/Lithium-Polymer Charge IC so you can charge an attached single-cell LiPo battery. The charge IC receives power from the USB connection and can source up to 450mA to charge an attached battery.

Photo highlighting the charging circuit
Batery charger for the mikroBUS™ carrier board. (Click to enlarge)

Status LEDs

The carrier board has two status LEDs:

  • 3V3 - This LED indicates when 3.3V power is available top the board.
  • CHG - This LED indicates the status of the charging circuit operation.

Photo highlighting the status LEDs
Status LEDs on the mikroBUS™ carrier board. (Click to enlarge)

Solder Jumpers

Users who have never worked with soldering jumpers and cutting PCB traces before (or for a quick refresher), check out our How to Work with Solder Jumpers and PCB Traces tutorial for detailed instructions and tips.

There are four adjustable solder jumpers on the mikroBUS™ carrier board labeled MEAS, BYP, 3.3V_VE and 3.3V. The table below briefly outlines their functionalities:

Jumper Name/Label Description Default State
Measure/MEAS Open this jumper to probe the current draw at the 3.3V output of the regulator. For help measuring current, take a look at our How to Use a Multimeter tutorial. CLOSED
Bypass/BYP The "penny-in-the-fuse" jumper. Bypasses the 6V/2A fuse and nets VIN and V_USB together. Close only if you know what you are doing! OPEN
Voltage Regulator Enable/VE Voltage regulator control. Close this jumper to control the VREG in low-power applications. OPEN
3.3V LED Power/3V3 LED Connects the 3.3V LED to 3.3V via a 1K Ohm resistor. Open to disable the LED. CLOSED

Jumpers on the mikroBUS™ carrier board. (Click to enlarge)

MicroMod Pinout

Since this carrier board is designed to work with all of the MicroMod Processors we've included the table below to outline which pins are used so, if you would like, you can compare them to the pinout tables in their respective Hookup Guides.

Function Bottom
(Not Connected) 75 GND
3.3V 74 73 G5 / BUS5
RTC_3V_BATT 72 71 G6 / BUS6
SPI_CS1# SDIO_DATA3 (I/O) 70 69 G7 / BUS7
SDIO_DATA2 (I/O) 68 67 G8
PDM_CLK PCM_CLK I2S_SCK AUD_BCLK 50 49 BATT_VIN / 3 (I - ADC) (0 to 3.3V)
G4 / BUS4 48 47 PWM1
G3 / BUS3 46 45 GND
G2 / BUS2 44 43 CAN_TX
G1 / BUS1 42 41 CAN_RX
G0 / BUS0 40 39 GND
A1 38 37 USBHOST_D-
A0 34 33 GND
PWM0 32 31 Module Key
Module Key 30 29 Module Key
Module Key 28 27 Module Key
Module Key 26 25 Module Key
Module Key 24 23 SWDIO
UART_TX2 (O) 22 21 SWDCK
UART_RX2 (I) 20 19 UART_RX1 (I)
CAM_TRIG D1 18 17 UART_TX1 (0)
I2C_INT# 16 15 UART_CTS1 (I)
I2C_SCL (I/0) 14 13 UART_RTS1 (O)
I2C_SDA (I/0) 12 11 BOOT (I - Open Drain)
D0 10 9 USB_VIN
SWO G11 8 7 GND
RESET# (I - Open Drain) 6 5 USB_D-
3.3V_EN 4 3 USB_D+
3.3V 2 1 GND
Signal Group Signal I/O Description Voltage
Power 3.3V I 3.3V Source 3.3V
GND Return current path 0V
USB_VIN I USB VIN compliant to USB 2.0 specification.
Connect to pins on Processor Board that require 5V for USB functionality.
RTC_3V_BATT I 3V provided by external coin cell or mini battery. Max draw = 100μA.
Connect to pins maintaining an RTC during power loss. Can be left NC.
3.3V_EN O Controls the carrier board's main voltage regulator. Voltage above 1V will enable 3.3V power path. 3.3V
BATT_VIN/3 I Carrier board raw voltage over 3. 1/3 resistor divider is implemented on carrier board.
Amplify the analog signal as needed for full 0-3.3V range
Reset Reset I Input to processor. Open drain with pullup on processor board. Pulling low resets processor. 3.3V
Boot I Input to processor. Open drain with pullup on processor board. Pulling low puts processor into special boot mode. Can be left NC. 3.3V
USB USB_D± I/O USB Data ±. Differential serial data interface compliant to USB 2.0 specification. If UART is required for programming, USB± must be routed to a USB-to-serial conversion IC on the processor board.
USB Host USBHOST_D± I/O For processors that support USB Host Mode. USB Data±. Differential serial data interface compliant to USB 2.0 specification. Can be left NC.
CAN CAN_RX I CAN Bus receive data. 3.3V
CAN_TX O CAN Bus transmit data. 3.3V
UART UART_RX1 I UART receive data. 3.3V
UART_TX1 O UART transmit data. 3.3V
UART_RTS1 O UART request to send. 3.3V
UART_CTS1 I UART clear to send. 3.3V
UART_RX2 I 2nd UART receive data. 3.3V
UART_TX2 O 2nd UART transmit data. 3.3V
I2C I2C_SCL I/O I2C clock. Open drain with pullup on carrier board. 3.3V
I2C_SDA I/O I2C data. Open drain with pullup on carrier board 3.3V
I2C_INT# I Interrupt notification from carrier board to processor. Open drain with pullup on carrier board. Active LOW 3.3V
I2C_SCL1 I/O 2nd I2C clock. Open drain with pullup on carrier board. 3.3V
I2C_SDA1 I/O 2nd I2C data. Open drain with pullup on carrier board. 3.3V
SPI SPI_COPI O SPI Controller Output/Peripheral Input. 3.3V
SPI_CIPO I SPI Controller Input/Peripheral Output. 3.3V
SPI_SCK O SPI Clock. 3.3V
SPI_CS# O SPI Chip Select. Active LOW. Can be routed to GPIO if hardware CS is unused. 3.3V
SPI/SDIO SPI_SCK1/SDIO_CLK O 2nd SPI Clock. Secondary use is SDIO Clock. 3.3V
SPI_COPI1/SDIO_CMD I/O 2nd SPI Controller Output/Peripheral Input. Secondary use is SDIO command interface. 3.3V
SPI_CIPO1/SDIO_DATA0 I/O 2nd SPI Peripheral Input/Controller Output. Secondary use is SDIO data exchange bit 0. 3.3V
SDIO_DATA1 I/O SDIO data exchange bit 1. 3.3V
SDIO_DATA2 I/O SDIO data exchange bit 2. 3.3V
SPI_CS1/SDIO_DATA3 I/O 2nd SPI Chip Select. Secondary use is SDIO data exchange bit 3. 3.3V
Audio AUD_MCLK O Audio master clock. 3.3V
AUD_OUT/PCM_OUT/I2S_OUT/CAM_MCLK O Audio data output. PCM synchronous data output. I2S serial data out. Camera master clock. 3.3V
AUD_IN/PCM_IN/I2S_IN/CAM_PCLK I Audio data input. PCM syncrhonous data input. I2S serial data in. Camera periphperal clock. 3.3V
AUD_LRCLK/PCM_SYNC/I2S_WS/PDM_DATA I/O Audio left/right clock. PCM syncrhonous data SYNC. I2S word select. PDM data. 3.3V
AUD_BCLK/PCM_CLK/I2S_CLK/PDM_CLK O Audio bit clock. PCM clock. I2S continuous serial clock. PDM clock. 3.3V
SWD SWDIO I/O Serial Wire Debug I/O. Connect if processor board supports SWD. Can be left NC. 3.3V
SWDCK I Serial Wire Debug clock. Connect if processor board supports SWD. Can be left NC. 3.3V
ADC A0 I Analog to digital converter 0. Amplify the analog signal as needed to enable full 0-3.3V range. 3.3V
A1 I Analog to digital converter 1. Amplify the analog signal as needed to enable full 0-3.3V range. 3.3V
PWM PWM0 O Pulse width modulated output 0. 3.3V
PWM1 O Pulse width modulated output 1. 3.3V
Digital D0 I/O General digital input/output pin. 3.3V
D1/CAM_TRIG I/O General digital input/output pin. Camera trigger. 3.3V
General/Bus G0/BUS0 I/O General purpose pins. Any unused processor pins should be assigned to Gx with ADC + PWM capable pins given priority (0, 1, 2, etc.) positions. The intent is to guarantee PWM, ADC and Digital Pin functionality on respective ADC/PWM/Digital pins. Gx pins do not guarantee ADC/PWM function. Alternative use is pins can support a fast read/write 8-bit or 4-bit wide bus. 3.3V
G1/BUS1 I/O 3.3V
G2/BUS2 I/O 3.3V
G3/BUS3 I/O 3.3V
G4/BUS4 I/O 3.3V
G5/BUS5 I/O 3.3V
G6/BUS6 I/O 3.3V
G7/BUS7 I/O 3.3V
G8 I/O General purpose pin 3.3V
G9/ADC_D-/CAM_HSYNC I/O Differential ADC input if available. Camera horizontal sync. 3.3V
G10/ADC_D+/CAM_VSYNC I/O Differential ADC input if available. Camera vertical sync. 3.3V
G11/SWO I/O General purpose pin. Serial Wire Output 3.3V
M.2 Pin# MicroMod Pin Name Board Connections Description
mikroBUS™ Socket - GND
Ground plane
2 3.3V 3.3V
mikroBUS™ Socket - +3.3V
Regulated 3.3V via USB-C
3 USB_D+ -- USB D+ connection for Processor Board
4 3.3V_EN -- Voltage regulator enable input
5 USB_D- -- USB D- connection for Processor Board
6 RESET RESET Button Connected to RESET Button
Reset is active LOW
9 USB_VIN mikroBUS™ Socket - +5V Input voltage from USB
10 D0 D0
mikroBUS™ Socket - INT
Digital I/O pin
11 BOOT BOOT Button Connected to BOOT Button
Boot is active LOW
Qwiic Connector - SDA
mikroBUS™ Socket - SDA
I2C data signal for Qwiic devices
Qwiic Connector - SCL
mikroBUS™ Socket - SCL
I2C clock signal for Qwiic devices
16 I2C_INT INT I2C interrupt pin
17 UART_TX1 mikroBUS™ Socket - TX UART transmit data pin
18 D1 D1
mikroBUS™ Socket - RST
Digital I/O pin
19 UART_RX1 mikroBUS™ Socket - RX UART receive data pin
32 PWM0 mikroBUS™ Socket - PWM PWM output pin
34 A0 mikroBUS™ Socket - AN ADC input pin
mikroBUS™ Socket - CS
SPI Chip Select
mikroBUS™ Socket - SCK
SPI Clock signal
mikroBUS™ Socket - MOSI
SPI Controller Out/Peripheral In signal
mikroBUS™ Socket - MISO
SPI Controller In/Peripheral Out signal

Breakout Pins

The mikroBUS™ carrier board features a 3.3V, a ground, seven I/O breakout pins. The functionality of these pins are detailed in the table above.

breakout pins
Breakout pins on the mikroBUS™ carrier board. (Click to enlarge)


The mikroBUS™ carrier board includes JTAG PTH pins for a JTAG header, to be used with one of the recommended MikroElektronica mikroProg programmers. The JTAG pins breakout the SWD (software debug) pins to the MicroMod processor board.

JTAG pins
JTAG pins on the mikroBUS™ carrier board. (Click to enlarge)

mikroBUS™ Socket

The most significant feature of this board, is the addition of the mikroBUS™ socket, which provides a drop-in interface for MikroElektronka's ecosystem of Click boards™ (over 1079 as of September 2021).

The mikroBUS™ socket comprises a pair of 8-pin female headers with a standardized pin configuration. The pins consists of three groups of communications pins (SPI, UART and I2C), six additional pins (PWM, Interrupt, Analog input, Reset and Chip select), and two power groups (3.3V and 5V).

mikroBUS™ socket
Standardized pin connections for the mikroBUS™ scoket. (Click to enlarge)

mikroBUS™ Socket
Pin Name
Carrier Board's
Processor Pin
mikroBUS™ Socket
I/O Direction
5V USB_VIN Input Power supply: 4.75~5.5V
3.3V 3.3V Input Power supply: 3.3V
GND - - Ground
SCK SCK (57) Input SPI - Clock signal
CIPO CIPO (59) Output SPI - Data from mikroBUS™ socket
COPI COPI (61) Input SPI - Data to mikroBUS™ socket
CS CS0 (55) Input SPI - Chip select for mikroBUS™ socket
SCL SCL (14) Input/Output I2C - Clock signal
SDA SDA (12) Input/Output I2C - Data signal to/from mikroBUS™ socket
TX TX1 (17) Input TX - Serial data to mikroBUS™ socket
RX RX1 (19) Output RX - Serial data from mikroBUS™ socket
RST D1 (18) Input Reset signal to mikroBUS™ socket
INT D0 (10) Output Interrupt trigger from mikroBUS™ socket
AN A0 (34) Output Analog output from mikroBUS™ socket
PWM PWM0 (32) Input PWM signal to mikroBUS™ socket

*For more information about the mikroBUS™ socket, click here for the mikroBUS™ standard specifications.

Qwiic Connector

The Qwiic connectors are provided for users to seamlessly integrate with SparkFun's Qwiic Ecosystem.

qwiic connectors
Qwiic connector on the MicroMod Qwiic carrier board. (Click to enlarge)

What is Qwiic?

The Qwiic system is intended a quick, hassle-free cabling/connector system for I2C devices. Qwiic is actually a play on words between "quick" and I2C or "iic".

Features of the Qwiic System

Keep your soldering iron at bay.

Cables plug easily between boards making quick work of setting up a new prototype. We currently offer three different lengths of Qwiic cables as well as a breadboard friendly cable to connect any Qwiic enabled board to anything else. Initially you may need to solder headers onto the shield to connect your platform to the Qwiic system but once that’s done it’s plug and go!

Qwiic Cable and Board

Qwiic cables connected to Spectral Sensor Breakout

Minimize your mistakes.

How many times have you swapped the SDA and SCL wires on your breadboard hoping the sensor will start working? The Qwiic connector is polarized so you know you’ll have it wired correctly, every time, from the start.

The PCB connector is part number SM04B-SRSS (Datasheet) or equivalent. The mating connector used on cables is part number SHR04V-S-B or equivalent. This is a common and low cost connector.

JST Connector

1mm pitch, 4-pin JST connector

Expand with ease.

It’s time to leverage the power of the I2C bus! Most Qwiic boards will have two or more connectors on them allowing multiple devices to be connected.