M-SoM from Boron or Argon migration guide

Pictures are not the same scale

Hardware

Module style

The primary difference is that the Argon and Boron are pin-based modules that can be installed in solderless breadboard for prototyping, can be installed in a socket on your custom board, or soldered directly to your board.

The M-SoM is a M.2 SoM that fits in a SMD mounted M.2 NGFF connector. It requires a base board and cannot be used on its own. The M.2 socket is not the same as the M.2 sockets used for flash memory in computers.

Datasheets

• M-SoM datasheet
• Boron BRN404X datasheet
• Boron datasheet
• B-Series evaluation board

Certification

When migrating to a new device, recertification is typically required. If you are using the standard Particle antennas you often only need to complete the less expensive unintentional radiator testing of your completed assembly, however in some cases intentional radiator testing could be required.

Software differences

User firmware binary size

One major advantage is that user firmware binaries can be up to 2048 Kbytes, instead of 256 Kbytes on Gen 3 devices using Device OS 3.1.0 or later.

Available RAM

The Boron and Argon have around 80K of RAM available to user applications. The M-SoM has 3500K of available RAM.

Flash file system

There is a 2 MB flash file system for storing user data. This is the same size as the Boron, B-SoM, and Argon. The Tracker has a 4 MB flash file system.

Status LED

The M-SoM does not include a status LED on the module. We recommend adding one to your base board.

Alternatively, if you have a separate hardware control panel, it provides the ability to put the RGB LED there and not duplicate it on the module or base board.

Device OS assumes a common anode RGB LED. One common LED that meets the requirements is the Cree CLMVC-FKA-CL1D1L71BB7C3C3 which is inexpensive and easily procured. You need to add three current limiting resistors. With this LED, we typically use 1K ohm current limiting resistors. These are much larger than necessary. They make the LED less blinding but still provide sufficient current to light the LEDs. If you want maximum brightness you should use the calculated values - 33 ohm on red, and 66 ohm on green and blue.

If you are using a different LED, you should limit current to 2mA per color.

A detailed explanation of different color codes of the RGB system LED can be found here.

Reset and Mode buttons

The M-SoM does not include buttons on module. We highly recommend including reset and mode buttons on your base board.

For example, you could use two-inexpensive SMD switches. The 4.5mm E-Switch TL3305AF160QG costs $0.20 in single quantities.

USB Connector

The M-SoM does not include a USB connector on the module. We recommend including one on your base board. This can be a USB Micro B, as on the Photon and Argon, or you could use USB C.

Since you choose the connector you have the option of using a right-angle USB connector. This is handy if your board will be an enclosure where the board is recessed into the case under a removable cover. This can allow the USB connector to be accessed without removing the board from the enclosure.

SWD/JTAG

The M-SoM does not include a SWD/JTAG debugging connector on the board. The functionality is available on four pads on the bottom of the SoM. These typically mate with pogo pins on your base board, if you want to include SWD functionality.

Since the M-SoM can be removed from your base board, you can also use a different board, such the M.2 SoM breakout board, for rare situations where you need SWD for low-level reprogramming.

Additionally, SWD is supported on pins on the M.2 connector:

• SWD is on the same pins as GPIO, so by default once user firmware boots, SWD is no longer available. This is the same as Gen 2 (STM32) but different than Gen 3 (nRF52840).
• SWO (Serial Wire Output) is not supported on the RTL8722DM.

Troubleshooting connector

In some cases, you may want to omit the reset and mode buttons, status LED, USB connector, and SWD/JTAG pins from your board board. If you do, we highly recommend adding a debug connector to make these features available for troubleshooting. The debug connector could be an actual connector, header pins, socket, card-edge connector, or SMD pads that allow an adapter or daughter card with these features.

Voltage regulators

VCC

VCC is used to supply power to the cellular module. The recommended input voltage range on this pin is between 3.6V to 4.2V DC. This can be connected directly to a 3.7V LiPo battery.

If you are not using a battery, or using a battery of a different voltage, you should use a regulator to supply 3.7V to 4.2V at 2A. You may want to add additional bulk capacitors to handle the short, high current peak usage when the cellular modem is transmitting.

3V3

3V3 is used to supply power to MCU, Wi-Fi, BLE, logic ICs, memory, etc.. Make sure that the supply can handle a minimum of 500 mA.

These limits do not include any 3.3V peripherals on your base board, so that may increase the current requirements.

Power supply requirements:

• 3.3V output
• Maximum 5% voltage drop
• 100 mV peak-to-peak ripple maximum
• 500 mA minimum output current at 3.3V recommended for future compatibility
• Maintain these values at no-load as well as maximum load

LiPo Battery and LI+ pin

The M-SoM does not include a LiPo battery connector or charging circuit on the module. If you want these features you will need to include them on your base board.

This is the LiPo battery connector used on the Argon:

As of the first half of 2022, supply chain constraints are affecting the supply of PMICs and charge controllers. Because of this, we are not recommending a specific model to use with your board.

The Argon uses a Torex XC6208A42 LiPo charge controller, however there is no need use this part and it will be difficult to obtain.

The Boron uses a full PMIC (bq24195) and fuel gauge (MAX17043). By including these features on your base board you can provide more full-featured operation on battery power than the Argon does.

EN pin

The Argon and Boron have EN pin which can shut down the Torex XC9258 3.3V regulator to power down the 3.3V supply to the Argon nRF52840 MCU and the ESP32 Wi-Fi coprocessor. A similar feature exists on the Boron, using a load switch to control the 3.3V power supply and the 3.7V cellular modem power supply.

This feature does not exist on the M-SoM, however you could add equivalent circuitry on your base board. This could either be a regulator with power control like the Argon, or an external load switch like the Boron (Torex XC8107). The specific load switch is not important, as long as it meets the power requirements of the MCU and any additional peripherals on 3V3.

Land pattern

The land pattern for the M.2 connector on the M-SoM is:

The Argon/Boron land pattern is:

ADC

• Same number of ADC on both
• ADC inputs are single-ended and limited to 0 to 3.3V on both
• Resolution is 12 bits on both

The ADCs on the M-SoM (RTL872x) have a lower impedance than other Particle device MCUs (nRF52, STM32F2xx). They require a stronger drive and this may cause issues when used with a voltage divider. This is particularly true for A7, which has an even lower impedance than other ADC inputs.

For signals that change slowly, such as NTC thermocouple resistance, you can add a 2.2 uF capacitor to the signal. For rapidly changing signals, a voltage follower IC can be used.

Serial

• One additional UART serial port on the M-SoM

SPI

• There are two SPI interfaces on both, however SPI1 is on different pins on M-SoM.

I2C

• 1 I2C on M-SoM vs. 2 on the B-Series SoM.
• You can generally have many devices on a single I2C bus.
• If you have I2C address conflicts you can use an I2C multiplexer like the TCA9548A.
• On the M-SoM (and P2 and Photon 2), the only valid I2C clock speeds are CLOCK_SPEED_100KHZ and CLOCK_SPEED_400KHZ. Other speeds are not supported at this time.

PWM

PDM

Pulse density modulation digital microphones can be used with the Microphone_PDM library and the M-SoM, but only on specific pins. The B-SoM can use any pins for PDM (with the same library).

Boot mode pins

These pins have a special function at boot. Beware when using these pins as input as they can trigger special modes in the MCU.

NFC

The M-SoM does not support NFC.

The Boron and Argon support NFC Tag mode.

Sleep

• In HIBERNATE sleep mode, the M-SoM can only be wakened via the WKP pin, but the Boron and Argon can be wakened by any pin.

• In STOP and ULTRA_LOW_POWER sleep modes, the M-SoM, Boron, and Argon can be wakened by any pin.

• In HIBERNATE sleep mode, the M-SoM puts OUTPUT pins into high-impedance state. The Boron and Argon preserve the digital level.

• In STOP and ULTRA_LOW_POWER sleep modes, the M-SoM, Boron, and Argon preserve the digital output

• In HIBERNATE sleep mode, on the M-SoM, pin D21 does not maintain INPUT_PULLUP or INPUT_PULLDOWN while asleep.

Full comparison

3V3

A0

A1

A2

A3

A4

A5

A5

A6

AGND

CELL USBD-

CELL USBD+

CELL VBUS

CELL_RI

D0

D1

D2

D20

D21

D22

D23

D24

D25

D26

D27

D3

D4

D5

D6

D7

D8

EN

GND

GNSS_TX

LI+

MISO

MODE

MOSI

NC

RGBB

RGBG

RGBR

RST

RX

SCK

SIM_CLK

SIM_DATA

SIM_RST

SIM_VCC

TX

USBDATA-

USBDATA+

VCC

VUSB

WKP

Software

Wi-Fi configuration

Since the Boron (cellular) does not have Wi-Fi support, if you wish to use Wi-Fi on the M-SoM you will need to provide a way to configure it. Wi-Fi setup works the same as the P2, Photon 2, and Argon, and uses BLE. See Wi-Fi setup options for more information.

User firmware binary size

One major advantage of the M-SoM is that user firmware binaries can be up to 2048 Kbytes.

On the B-SoM (Device OS 3.1 and later), it's 256 Kbytes, or 128 Kbytes for older version of Device OS.

Platform ID

The Platform ID of the msom (35, PLATFORM_MSOM) is different from that of the Boron (13) because of the vastly different hardware.

If you have a product based on the Boron, you will need to create a separate product for devices using the M-SoM. While you may be able to use the same source code to build your application, the firmware binaries uploaded to the console will be different, so they need to be separate products. This generally does not affect billing as only the number of devices, not the number of products, is counted toward your plan limits.

Third-party libraries

Most third-party libraries are believed to be compatible. The exceptions include:

• Libraries for MCU-specific features (such as ADC DMA)
• Libraries that are hardcoded to support only certain platforms by their PLATFORM_ID
• Libraries that manipulate GPIO at high speeds or are timing-dependent

DS18B20 (1-Wire temperature sensor)

• Not compatible
• OneWire library requires high-speed GPIO support
• Can use DS2482 I2C to 1-Wire bridge chip instead
• SHT30 sensors (I2C) may be an alternative in some applications

FastLED

• Not compatible.
• In theory the library could be modified to use the same technique as the NeoPixel library.

NeoPixel (WS2812, WS2812B, and WS2813)

• Requires Device OS 5.3.2 or later and Particle-NeoPixel version 1.0.3.

OneWire

• Not compatible
• OneWire library requires high-speed GPIO support
• Can use DS2482 I2C to OneWire bridge instead

DHT22 and DHT11 (temperature and humidity sensor)

• Not compatible, requires high-speed GPIO support
• Using an I2C temperature and humidity sensor like the SHT3x is recommended instead

SHT1x (temperature and humidity sensor)

• Not compatible, requires high-speed GPIO support
• SHT3x using I2C is recommended

SparkIntervalTimer

• Not compatible at this time
• Requires hardware timer support from user firmware

Revision history