Design-Your-Arduino-Nano-33-IoT

0. Introduction

Arduino Nano 33 IoT is a great board with BLE, WiFi, IMU. It can be used as a mainboard of projects, and using breadboard to connect more peripherals. It is a simple and quick way for research. In addition, we can design a PCB with the desired peripheral functionality by just leaving pad locations for the Arduino Nono 33 IoT and soldering it on. In this project, based on the official open source (Schematics and Eagle files), I designed a new Arduino 33 Nano IoT and added the TB6612 and UWB module as peripherals (As shown below).

1. PCB design

I will not introduce this part too much. The main schematic refers to the official documents, and then add some peripherals needed for your project, such as sensor interfaces, motor drivers, etc.

2. Bootloader

The article about how to burn the bootloader on Arduino Nano 33 IoT can be found on the Arduino official website. There are two methods, I chose to use Arduino MKR Zero as a programmer to do this task, and a SanDisk Ultra 128G SD card. Then we can follow the instructions, but I found the codes need to be tuned a little.

1. Download the bootloader binary, rename it to fw.bin, and move this file to SD card.
2. Insert the SD card into Arduino MKR Zero, connect the board to computer using USB cable.
3. Open Arduino IDE, install Adafruit DAP library.
4. Open flash_from_SD_nkrzero.ino file in this repository using Arduino IDE, and upload to Arduino MKR Zero. We will see below messages in serial monitor.

Note: In the official steps, we select File > Examples > Adafruit DAP library > samd21 > flash_from_SD from the Arduino IDE's menus. However, this sketch has some issues when we use Arduino MKR Zero as programmer.

• GCC 4.4 warnings
• Card failed, or not present

5. Connect the programmer Arduino board (Arduino MKR Zero) to the target Arduino board (your board) as follows:

Programmer board	Target board (Nano 33 IoT)
VCC	+3.3V
10	SWDIO
9	SWCLK
GND	GND
11	RST

Here I use a PIN PROBE CLIP, which can connect two boards together easily.

6. Press the reset button on the Arduino MKR Zero. Following messages should be shown in serial monitor.

3. Firmware

After burn the bootloader, we also need to install the firmware, otherwise some modules such as BlueTooth can't work well.

1. Plug the USB cable of the new Arduino Nano 33 IoT board into your computer.

2. Select the target board.

3. Tools > Firmware Updater > select board > check updates > install

• Firmware: Installation failed. Please try again.

After finishing above steps, a new Arduino Nano 33 IoT is made.

4. Issues

4.1 GCC 4.4 warnings

The Adafruit DAP library is used. The following warnings maybe show:

\Documents\Arduino\libraries\Adafruit_DAP_library\Adafruit_DAP_SAM.h:166:40: note: offset of packed bit-field 'Adafruit_DAP_SAMx5::<unnamed union>::<unnamed struct>::<anonymous>' has changed in GCC 4.4

It is not urgent to be solved, just warnings not errors. But if we would like to solve these warnings, can open Adafruit_DAP_SAM.h in the following directories:

\Documents\Arduino\libraries\Adafruit_DAP_library\Adafruit_DAP_SAM.h

Replace lines 165-190 of the code with the following (Change all uint8_t -> uint16_t):

  typedef union {
    struct __attribute__((__packed__)) {
      uint16_t BOD33_Disable : 1;
      uint16_t BOD33_Level : 8;
      uint16_t BOD33_Action : 2;
      uint16_t BOD33_Hysteresis : 4;
      uint16_t : 8;
      uint16_t : 3;
      uint16_t NVM_BOOT : 4;
      uint16_t : 2;
      uint16_t SEESBLK : 4;
      uint16_t SEEPSZ : 3;
      uint16_t RAM_ECCDIS : 1;
      uint16_t : 8;
      uint16_t WDT_Enable : 1;
      uint16_t WDT_Always_On : 1;
      uint16_t WDT_Period : 4;
      uint16_t WDT_Window : 4;
      uint16_t WDT_EWOFFSET : 4;
      uint16_t WDT_WEN : 1;
      uint16_t : 1;
      uint16_t NVM_LOCKS : 32; // As per SAM D5x/E5x Family datasheet page 53
      uint32_t User_Page : 32;
    } bit;
    uint8_t reg[USER_ROW_SIZE];
  } USER_ROW;

4.2 Card failed, or not present

If we follow the official instructions, we will perhaps find function SD.begin() cannot work, and the following text on the serial monitor.

Card failed, or not present

We can make the following modefication for the example codes.

• Step 1

The pin correspondence is as follows, so we need to change pins define.

Programmer board	Target board (Nano 33 IoT)
VCC	+3.3V
10	SWDIO
9	SWCLK
GND	GND
11	RST

Replace lines 6-8:

#define SWDIO 10
#define SWCLK 9
#define SWRST 11

• Step 2

Below line 11, add the following codes at lines 12-28:

#ifndef SDCARD_SS_PIN
const uint8_t SD_CS_PIN = SS;
#else  // SDCARD_SS_PIN
// Assume built-in SD is used.
const uint8_t SD_CS_PIN = SDCARD_SS_PIN;
#endif  // SDCARD_SS_PIN

// Try max SPI clock for an SD. Reduce SPI_CLOCK if errors occur.
#define SPI_CLOCK SD_SCK_MHZ(50)

#if HAS_SDIO_CLASS
#define SD_CONFIG SdioConfig(FIFO_SDIO)
#elif  ENABLE_DEDICATED_SPI
#define SD_CONFIG SdSpiConfig(SD_CS_PIN, DEDICATED_SPI, SPI_CLOCK)
#else  // HAS_SDIO_CLASS
#define SD_CONFIG SdSpiConfig(SD_CS_PIN, SHARED_SPI, SPI_CLOCK)
#endif  // HAS_SDIO_CLASS

Then replace lines 55-57:

  if (!SD.begin(SD_CONFIG)) {
    error("Card failed, or not present");
  }

• Step 3

We should check the SD card format first, here I use SanDisk Ultra 128G, so some codes need to be tuned.

Replace line 36 from:

SdFat SD;

to

SdExFat SD;

Replace line 60 from:

 File32 dataFile = SD.open(FILENAME);

to

 ExFile dataFile = SD.open(FILENAME);

4.3 Firmware: Installation failed. Please try again.

When we first install firmware, sometimes will meet this error.

At this time, we just seltect the board and install firmware again, usually the problem will be solved.

4.4 Starting Bluetooth® Low Energy failed!

Some BLE examples will include following codes:

  // begin initialization
  if (!BLE.begin()) {
    Serial.println("starting Bluetooth® Low Energy failed!");

    while (1);
  }

If we don't install firmware, BLE.begin() function can't work.