MicroMod nRF52840 Processor Hookup Guide

Contributors: El Duderino, MAKIN-STUFF

Hardware Overview

In this section we'll cover the nRF52840 SoC in more detail as well as other components included on the MicroMod nRF52840 Processor.

M.2 Connector

All of our MicroMod Processors come equipped with the M.2 MicroMod Connector, which leverages the M.2 standard and specification to allow you to install your MicroMod Processor board on your choice of Carrier Board.

M2 Connector from the Front	M2 Connector from the Back

nRF52840 MDBT50Q Module

This Processor features the nRF52840 SoC from Nordic Semiconductor. The specific module is from Raytac which includes a built-in PCB antenna. Refer to the MDBT50Q Module Datasheet and nRF52840 IC Datasheet for full specifications on the IC and module.

The nRF52840 combines an ARM Cortex-M4 CPU and 2.4 GHz Bluetooth transceiver to provide a versatile and powerful microcontroller with Bluetooth 5.0 wireless capability. The transceiver also works with Bluetooth mesh, IEEE 802.15.4(Thread & Zigbee), ANT and Nordic's proprietary 2.5 GHz RF protocol to communicate with other Nordic devices.

The nRF52840 Processor board uses the Arduino Nano 33 BLE Bootloader as opposed to the USB Bootloader found on the SparkFun Pro nRF52840 Mini.

Flash IC

Along with the nRF52840 module, the Processor also includes external flash memory in the form of the 128Mb (16M x 8) W25Q128JV SpiFlash IC from Winbond Electronics. The flash IC is connected via SPI on the nRF52840. For full details on the Flash IC, refer to the datasheet.

The flash IC uses the secondary SPI bus (SPI1) and its Chip Select pin is tied to a dedicated pad on the nRF module (P0.12). Writing to the flash IC requires some extra work involving adjusting the SPI definitions in the variant file and is not recommended for anyone but advanced users. Writing to the Flash IC is beyond the scope of this tutorial.

STAT LED

The STAT LED is tied to a dedicated pin on the nRF module (P0.13) and can be used as a status LED or as a built-in LED. Control it directly in Arduino by writing to LED_BUILTIN.

nRF52840 Processor Pin Functions

The nRF52840 has a ton of awesome features including (but not limited to):

• ARM Cortex-M4 CPU with floating point unit (FPU), 64MHz
  • 1MB internal Flash -- For all of your program, SoftDevice, and file-storage needs!
  • 256kB internal RAM -- For your stack and heap storage.
• Integrated 2.4GHz radio with support for:
  • Bluetooth Low Energy (BLE) -- With peripheral and/or central BLE device support
  • Bluetooth 5 -- Mesh Bluetooth!
  • Nordic's proprietary RF protocol -- If you want to communicate securely with other Nordic devices.
• Interface Options
  • USB -- Turn your nRF52840 into a USB mass-storage device, use a CDC (USB serial) interface, and more.
  • UART -- Serial interfaces with support for hardware flow-control if desired.
  • I²C -- SparkFun's favorite 2-wire bi-directional bus interface
  • SPI -- If you prefer the 3+-wire serial interface
  • Analog-to-digital converters (ADC) -- Six pins on the nRF52840 Processor support analog inputs though four are used for other functionality on the MicroMod Processor.
  • PWM -- Two dedicated Pulse-Width Modulation interface pins.
  • PDM -- Pulse Density Modulation interface. The PDM module generates the PDM clock and supports single and dual channel data input.
  • GPIO -- Eleven dedicated General Purpose I/O pins.

I²C

As you may have guessed from our extensive Qwiic System, we love communicating with devices using I²C! The nRF52840 Processor features two I²C buses. The main I²C bus has dedicated pins connected to MiroMod pads 12/14, along with a dedicated Interrupt pin connected to MicroMod pad 16. The primary I²C Bus will almost always be connected to a Qwiic connector on your Carrier Board.

If you want a second I²C bus, the nRF52840 has SDA1 and SCL1 on MicroMod pads 51 and 53. To use this second bus, initialize it by calling Wire1.begin();.

UART

The nRF52840 Processor has three UARTs available. The primary UART is tied to USB_D± (MicroMod pads 3 and 5) for serial communication over USB. This is used for your standard serial upload as well as serial prints in Arduino. The secondary UART is a hardware UART tied to MicroMod pads 19 (RX1) and 17 (TX1). The tertiary UART is another hardware UART tied to MicroMod pads 20 (RX2) and 22 (TX2).

In Arduino, use the following calls to send data over the three UARTs:

• Serial - Communication over USB
• Serial1 - Communication over RX1/TX1
• Serial2 - Communication over RX2/TX2

SPI

The nRF52840 Processor features two SPI buses; SPI & SPI1. The primary SPI bus is tied to MicroMod pads listed below:

• CIPO (Controller In/Peripheral Out) - MicroMod pad 61
• COPI (Controller Out/Peripheral In) - MicroMod pad 59
• SCK (Serial Clock) - MicroMod pad 57
• CS (Chip Select) - MicroMod pad 55

SPI1 is tied to the flash IC and the pins are broken out to the M.2 connector on the MicroMod pads listed below:

• CIPO1/SDIO_DATA0 - MicroMod pad 64
• COPI1/SDIO_CMD - MicroMod pad 62
• SCK1/SDIO_CLK - MicroMod pad 60
• CS1/SDIO_DATA3 - MicroMod pad 70
• SDIO_DATA1 - MicroMod pad 66
• SDIO_DATA2 - MicroMod pad 68

Audio

The nRF52840 supports audio input processing through Pulse-Density Modulation (PDM). The pins used are:

• PDM_DATA - P0.26 , MicroMod pad 52. This is the PDM data signal.
• PDM_CLOCK - P0.25, MicroMod pad 50. This is the PDM clock signal.

For more information on how to process audio signals using PDM on the nRF52840 Processor, refer to section 6.15 of the nRF52480 Datasheet as well as this example for the MicroMod Machine Learning Carrier Board.

Dedicated Pins/GPIO

Finally, along with all the interface options, the nRF52840 Processor has two pins dedicated for each of the following functionalities: Analog Read/Input, Digital I/O and Pulse Width Modulation. The nRF52840 Processor also has eleven general purpose I/O pins.

Dedicated Pins

• A0 - ADC0/P0.04 , MicroMod pad 34 (Input Only!)
• A1 - ADC1/P0.05 , MicroMod pad pad 38 (Input Only!)
• D0 - P0.27 , MicroMod pad pad 10
• D1 - P1.08 , MicroMod pad pad 18
• PWM0 - P0.06 , MicroMod pad pad 32
• PWM1 - P0.16 , MicroMod pad pad 47

General Purpose I/O pins

• G0 - GPIO0/P0.29 , MicroMod pad 40
• G1 - GPIO1/P0.03 , MicroMod pad 42
• G2 - GPIO2/P1.13 , MicroMod pad 44
• G3 - GPIO3/P1.12 , MicroMod pad 46
• G4 - GPIO4/P1.11 , MicroMod pad 48
• G5 - GPIO5/P0.17 , MicroMod pad 73
• G6 - GPIO6/P1.06 , MicroMod pad 71
• G7 - GPIO7/P1.04 , MicroMod pad 69
• G8 - GPIO8/P1.14 , MicroMod pad 67
• G9 - GPIO9/P0.09 , MicroMod pad 65 - Shared with NFC1
• G10 - GPIO10/P0.10 , MicroMod pad 63 - Shared with NFC2

MicroMod Pinout

Users looking for a complete pin map can find it the table below or you can refer to the schematic.

• nRF52840 Processor Pinout Table
• MicroMod General Pinout Table
• MicroMod General Pin Descriptions

Board Dimensions

MicroMod Processor Boards all measure in at 22mm x 22mm, with 15mm to the top notch and 12mm to the E key. For more information regarding the processor board physical standards, head on over to the Getting Started with MicroMod tutorial and check out the Hardware Overview section.