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.

Argon

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

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.

Part Example Price
USB micro B connector Amphenol FCI 10118194-0001LF $0.42
CONN RCPT USB2.0 MICRO B SMD R/A Amphenol FCI 10118194-0001LF $0.42

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:

Pin Pin Name Description Interface MCU
43 A5 / D14 A5 Analog in, PWM, GPIO, shared with pin 53 SWCLK PB[3]
53 A5 / D14 A5 Analog in, PWM, GPIO, SWCLK, shared with pin 43 SWCLK PB[3]
55 D27 D27 GPIO, SWDIO (SWD_DATA), do not pull down at boot SWDIO PA[27]
  • 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:

Description Example Price
JST-PH battery connector JST B2B-PH-K-S-LF-SN $0.17

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:

M.2 Connector
Keep-Out Area

The Argon/Boron land pattern is:

Boron Land Pattern

ADC

Boron Pin Name Boron ADC M-SoM Pin M-SoM Pin Name M-SoM ADC
A0 / D19 23 A0 / D19
A1 / D18 33 A1 / D18
A2 / D17 35 A2 / D17
A3 / D16 37 A3 / D16
A4 / D15 41 A4 / D15
A5 / D14 43 A5 / D14
    53 A5 / D14
    45 A6 / D29
D8 / WKP   47 A7 / WKP
  • 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

Boron Pin Name Boron Serial M-SoM Pin M-SoM Pin Name M-SoM Serial
D2 Serial1 RTS 42 D2 Serial1 (RTS)
    58 D24 Serial2 (TX)
    60 D25 Serial2 (RX)
D3 Serial1 CTS 40 D3 Serial1 (CTS)
RX / D10 Serial1 RX 38 RX / D10 Serial1 (RX)
TX / D09 Serial1 TX 36 TX / D9 Serial1 (TX)
  • One additional UART serial port on the M-SoM

SPI

Boron Pin Name Boron I2C M-SoM Pin M-SoM Pin Name M-SoM I2C
D0 Wire (SDA) 22 D0 Wire (SDA)
D1 Wire (SCL) 20 D1 Wire (SCL)
  • There are two SPI interfaces on both, however SPI1 is on different pins on M-SoM.

I2C

Pin B-SoM Pin Name B-SoM I2C M-SoM Pin Name M-SoM I2C
20 D1 Wire (SCL) D1 Wire (SCL)
22 D0 Wire (SDA) D0 Wire (SDA)
40 D3 Wire1 (SCL) D3  
42 D2 Wire1 (SDA) D2  
  • 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

Boron Pin Name Boron PWM M-SoM Pin M-SoM Pin Name M-SoM PWM
A0 / D19 23 A0 / D19
A1 / D18 33 A1 / D18
A2 / D17 35 A2 / D17  
A3 / D16 37 A3 / D16  
A4 / D15 41 A4 / D15  
A5 / D14 43 A5 / D14
    53 A5 / D14
    45 A6 / D29
D2 42 D2  
D3 40 D3  
D4 66 D4
D5 68 D5
D6 70 D6
D7 72 D7
MISO / D11   50 MISO / D11
MOSI / D12   52 MOSI / D12
RX / D10   38 RX / D10
TX / D09   36 TX / D9
D8 / WKP 47 A7 / WKP  

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.

Pin Pin Name Description MCU
43 A5 / D14 SWCLK. 40K pull-down at boot. PB[3]
53 A5 / D14 SWCLK. 40K pull-down at boot. PB[3]
55 D27 SWDIO. 40K pull-up at boot. Low at boot triggers MCU test mode. PA[27]
58 D24 Low at boot triggers ISP flash download PA[7]
60 D25 Goes high at boot PA[8]
61 RGBR Low at boot triggers trap mode PA[30]

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.

Pin Pin Name Description Interface MCU
17 D21 D21 GPIO No internal pull up or pull down in HIBERNATE sleep mode. PA[0]
47 A7 / WKP A7 Analog In, WKP, GPIO D28 Only this pin can wake from HIBERNATE sleep mode. PA[20]

Full comparison

3V3

Boron M-SoM
  Pin Name 3V3 3V3
Description Regulated 3.3V DC output, maximum load 1000 mA System power in, supply a fixed 3.3V power, 500 mA minimum

A0

Boron M-SoM
  Pin Name A0 A0
  Pin Alternate Name D19 D19
  Description A0 Analog in, GPIO, PWM A0 Analog in, GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
  Supports analogWrite (PWM) Yes Yes
Supports tone A0, A1, A2, and A3 must have the same frequency. Yes
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 42K

A1

Boron M-SoM
  Pin Name A1 A1
  Pin Alternate Name D18 D18
  Description A1 Analog in, GPIO, PWM A1 Analog in, GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
  Supports analogWrite (PWM) Yes Yes
Supports tone A0, A1, A2, and A3 must have the same frequency. Yes
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

A2

Boron M-SoM
  Pin Name A2 A2
  Pin Alternate Name D17 D17
Description A2 Analog in, GPIO, PWM A2 Analog in, GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
Supports analogWrite (PWM) Yes No
Supports tone A0, A1, A2, and A3 must have the same frequency. No
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 22K

A3

Boron M-SoM
  Pin Name A3 A3
  Pin Alternate Name D16 D16
Description A3 Analog in, GPIO, PWM A3 Analog in, GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
Supports analogWrite (PWM) Yes No
Supports tone A0, A1, A2, and A3 must have the same frequency. No
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 2.1K

A4

Boron M-SoM
  Pin Name A4 A4
  Pin Alternate Name D15 D15
Description A4 Analog in, GPIO, PWM A4 Analog in, GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
Supports analogWrite (PWM) Yes No
Supports tone A4, A5, D2, and D3 must have the same frequency. No
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 2.1K

A5

Boron M-SoM
  Pin Name A5 A5
  Pin Alternate Name D14 D14
Description A5 Analog in, GPIO, PWM, SPI SS A5 Analog in, PWM, GPIO, shared with pin 53
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
  Supports analogWrite (PWM) Yes Yes
Supports tone A4, A5, D2, and D3 must have the same frequency. Yes
SPI interface SS. Use SPI object. This is only the default SS/CS pin, you can use any GPIO instead. n/a
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???
SWD interface n/a SWCLK. 40K pull-down at boot.
Signal used at boot n/a SWCLK. 40K pull-down at boot.

A5

Added to M-SoM
Pin Name A5
Pin Alternate Name D14
Description A5 Analog in, PWM, GPIO, SWCLK, shared with pin 43
Supports digitalRead Yes
Supports digitalWrite Yes
Supports analogRead Yes
Supports analogWrite (PWM) Yes
Supports tone Yes
Supports attachInterrupt Yes
Internal pull resistance 42K
SWD interface SWCLK. 40K pull-down at boot.
Signal used at boot SWCLK. 40K pull-down at boot.

A6

Added to M-SoM
Pin Name A6
Pin Alternate Name D29
Description A6 Analog in, GPIO, PWM, M.2 eval PMIC INT
Supports digitalRead Yes
Supports digitalWrite Yes
Supports analogRead Yes
Supports analogWrite (PWM) Yes
Supports tone Yes
Supports attachInterrupt Yes
Internal pull resistance ???

AGND

Added to M-SoM
Pin Name AGND
Description Analog Ground.

CELL USBD-

Added to M-SoM
Pin Name CELL USBD-
Description Cellular Modem USB Data-
Input is 5V Tolerant Yes

CELL USBD+

Added to M-SoM
Pin Name CELL USBD+
Description Cellular Modem USB Data+
Input is 5V Tolerant Yes

CELL VBUS

Added to M-SoM
Pin Name CELL VBUS
Description USB detect pin for cellular modem. 5V on this pin enables the Cellular Modem USB interface.
Input is 5V Tolerant Yes

CELL_RI

Added to M-SoM
Pin Name CELL_RI
Description CELL_RI, ring indicator output, leave unconnected.

D0

Boron M-SoM
  Pin Name D0 D0
Description I2C SDA, GPIO D0 GPIO, I2C SDA
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
I2C interface SDA. Use Wire object. SDA. Use Wire object. Use 1.5K to 10K external pull-up resistor.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D1

Boron M-SoM
  Pin Name D1 D1
Description I2C SCL, GPIO D1 GPIO, I2C SCL
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
I2C interface SCL. Use Wire object. SCL. Use Wire object. Use 1.5K to 10K external pull-up resistor.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D2

Boron M-SoM
  Pin Name D2 D2
Description SPI1 SCK, Serial1 RTS, GPIO, PWM D2 GPIO, Serial RTS flow control (optional), SPI1 SCK
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) Yes No
Supports tone A4, A5, D2, and D3 must have the same frequency. No
  UART serial RTS. Use Serial1 object. RTS. Use Serial1 object.
  SPI interface SCK. Use SPI1 object. SCK. Use SPI1 object.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D21

Added to M-SoM
Pin Name D21
Description D21 GPIO
Supports digitalRead Yes
Supports digitalWrite Yes
Supports attachInterrupt Yes
Internal pull resistance 22K. No internal pull up or pull down in HIBERNATE sleep mode.

D22

Added to M-SoM
Pin Name D22
Description D22 GPIO
Supports digitalRead Yes
Supports digitalWrite Yes
Supports attachInterrupt Yes
Internal pull resistance ???

D23

Added to M-SoM
Pin Name D23
Description D23 GPIO
Supports digitalRead Yes
Supports digitalWrite Yes
Supports attachInterrupt Yes
Internal pull resistance ???

D24

Added to M-SoM
Pin Name D24
Description D24 GPIO, Serial2 TX, do not pull down at boot
Supports digitalRead Yes
Supports digitalWrite Yes
UART serial TX. Use Serial2 object.
Supports attachInterrupt Yes
Internal pull resistance 42K
Signal used at boot Low at boot triggers ISP flash download

D25

Added to M-SoM
Pin Name D25
Description GPIO25, Serial2 RX
Supports digitalRead Yes
Supports digitalWrite Yes
UART serial RX. Use Serial2 object.
Supports attachInterrupt Yes
Internal pull resistance 42K
Signal used at boot Goes high at boot

D26

Added to M-SoM
Pin Name D26
Description D26 GPIO
Supports digitalRead Yes
Supports digitalWrite Yes
Supports attachInterrupt Yes
Internal pull resistance ???

D27

Added to M-SoM
Pin Name D27
Description D27 GPIO, SWDIO (SWD_DATA), do not pull down at boot
Supports digitalRead Yes
Supports digitalWrite Yes
Supports attachInterrupt Yes
Internal pull resistance 42K
SWD interface SWDIO. 40K pull-up at boot.
Signal used at boot SWDIO. 40K pull-up at boot. Low at boot triggers MCU test mode.

D3

Boron M-SoM
  Pin Name D3 D3
Description SPI1 MOSI, Serial1 CTS, PWM, GPIO D3 GPIO, Serial1 CTS flow control (optional), SPI1 SS
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) Yes No
Supports tone A4, A5, D2, and D3 must have the same frequency. No
  UART serial CTS. Use Serial1 object. CTS. Use Serial1 object.
SPI interface MOSI. Use SPI1 object. SS. Use SPI1 object.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D4

Boron M-SoM
  Pin Name D4 D4
Description SPI1 MISO, PWM, GPIO D4 GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogWrite (PWM) Yes Yes
Supports tone D4, D5, D6, and D7 must have the same frequency. Yes
SPI interface MISO. Use SPI1 object. n/a
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D5

Boron M-SoM
  Pin Name D5 D5
Description PWM, GPIO D5 GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogWrite (PWM) Yes Yes
Supports tone D4, D5, D6, and D7 must have the same frequency. Yes
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D6

Boron M-SoM
  Pin Name D6 D6
Description PWM, GPIO D6 GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogWrite (PWM) Yes Yes
Supports tone D4, D5, D6, and D7 must have the same frequency. Yes
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D7

Boron M-SoM
  Pin Name D7 D7
Description PWM, GPIO D7 GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) PWM is shared with the RGB LED, you can specify a different duty cycle but should not change the frequency. Yes
Supports tone No Yes
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

D8

Added to M-SoM
Pin Name D8
Description D8 GPIO, SPI SS
Supports digitalRead Yes
Supports digitalWrite Yes
SPI interface Default SS for SPI.
Supports attachInterrupt Yes
Internal pull resistance 2.1K

EN

Removed from Boron
Pin Name EN
Description Power supply enable. Connect to GND to power down. Has internal weak (100K) pull-up.

GND

Unchanged between Boron and M-SoM
Pin Name GND
Description Ground.

GNSS_TX

Added to M-SoM
Pin Name GNSS_TX
Description Cellular modem GNSS UART TX

LI+

Removed from Boron
Pin Name LI+
Description Connected to JST PH LiPo battery connector. 3.7V in or out.

MISO

Boron M-SoM
  Pin Name MISO MISO
  Pin Alternate Name D11 D11
Description SPI MISO, GPIO D11 GPIO, PWM, SPI MISO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  SPI interface MISO. Use SPI object. MISO. Use SPI object.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 2.1K

MODE

Boron M-SoM
Pin Name MODE D20
Pin Alternate Name D20 n/a
Description MODE button, has internal pull-up D20 GPIO
Supports digitalRead n/a Yes
Supports digitalWrite n/a Yes
Supports attachInterrupt n/a Yes
Internal pull resistance n/a ???

MODE

Added to M-SoM
Pin Name MODE
Description MODE button. Pin number constant is BTN. External pull-up required!
Supports attachInterrupt Yes

MOSI

Boron M-SoM
  Pin Name MOSI MOSI
  Pin Alternate Name D12 D12
Description SPI MOSI, GPIO D12 GPIO, PWM, SPI MOSI
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  SPI interface MOSI. Use SPI object. MOSI. Use SPI object.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 2.1K

NC

Added to M-SoM
Pin Name NC
Description n/a

RGBB

Added to M-SoM
Pin Name RGBB
Description RGB LED Blue

RGBG

Added to M-SoM
Pin Name RGBG
Description RGB LED Green

RGBR

Added to M-SoM
Pin Name RGBR
Description RGB LED Red
Signal used at boot Low at boot triggers trap mode

RST

Boron M-SoM
  Pin Name RST RST
Description Hardware reset. Pull low to reset; can leave unconnected in normal operation. Hardware reset, active low. External pull-up required.

RX

Boron M-SoM
  Pin Name RX RX
  Pin Alternate Name D10 D10
Description Serial RX, GPIO Serial RX, PWM, GPIO, SPI1 MISO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  UART serial RX. Use Serial1 object. RX. Use Serial1 object.
SPI interface n/a MISO. Use SPI1 object.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 2.1K

SCK

Boron M-SoM
  Pin Name SCK SCK
  Pin Alternate Name D13 D13
Description SPI SCK, GPIO D13 GPIO, SPI SCK
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  SPI interface SCK. Use SPI object. SCK. Use SPI object.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 2.1K

SIM_CLK

Added to M-SoM
Pin Name SIM_CLK
Description Leave unconnected, 1.8V/3V SIM Clock Output from cellular modem.

SIM_DATA

Added to M-SoM
Pin Name SIM_DATA
Description Leave unconnected, 1.8V/3V SIM Data I/O of cellular modem with internal 4.7 k pull-up.

SIM_RST

Added to M-SoM
Pin Name SIM_RST
Description Leave unconnected, 1.8V/3V SIM Reset Output from cellular modem.

SIM_VCC

Added to M-SoM
Pin Name SIM_VCC
Description Leave unconnected, 1.8V/3V SIM Supply Output from R410M.

TX

Boron M-SoM
  Pin Name TX TX
Pin Alternate Name D09 D9
Description Serial TX, GPIO Serial TX, PWM, GPIO, SPI1 MOSI
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  UART serial TX. Use Serial1 object. TX. Use Serial1 object.
SPI interface n/a MOSI. Use SPI1 object.
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K 2.1K

USBDATA-

Added to M-SoM
Pin Name USBDATA-
Description USB Data-
Input is 5V Tolerant Yes

USBDATA+

Added to M-SoM
Pin Name USBDATA+
Description USB Data+
Input is 5V Tolerant Yes

VCC

Added to M-SoM
Pin Name VCC
Description System power in, connect to the +LiPo or supply a fixed 3.6-4.3V power.

VUSB

Removed from Boron
Pin Name VUSB
Description Power out (when powered by USB) 5 VDC at 1A maximum. Power in with limitations.
Input is 5V Tolerant Yes

WKP

Boron M-SoM
Pin Name D8 A7
  Pin Alternate Name WKP WKP
Description GPIO, PWM A7 Analog In, WKP, GPIO D28
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead No Yes
Supports analogWrite (PWM) Yes No
Supports tone D4, D5, D6, and D7 must have the same frequency. No
Supports attachInterrupt Yes. You can only have 8 active interrupt pins. Yes
Internal pull resistance 13K ???

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)

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

Revision Date Author Comments
pre 2023-10-03 RK Initial version
2023-12-20 RK Additional notes for ADCs, D24, and D25
001 2024-04-02 RK General availability