M-SoM from P2 migration guide

Pictures are not the same scale

The P2 module is a Wi-Fi SMD module that is mounted directly to your custom base board, while the M-SoM is a M.2 SoM that fits in a M.2 socket on your base board and has both cellular and Wi-Fi capabilities. The Particle M-SoM is larger and will not fit in the same footprint as the P2.

However, since the P2 has a Realtek RTL8721DM processor and the M-SoM has a Realtek RTL8722DM which is substantially similar, only having more GPIO, the migration should be relatively straightforward.

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.

Hardware

Antenna

The P2 has a choice between an internal trace antenna on the module or an external antenna for Wi-Fi and BLE (shared) connected by a U.FL connector.

The M-SoM requires an external antenna for cellular. It also requires a separate external antenna for Wi-Fi and BLE (shared). All antennas are connected by U.FL connectors.

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.

The P2 does not require this voltage.

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

Land pattern

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

M.2 Connector
Keep-Out Area

The P2 land pattern is:

P2 Land Pattern

ADC

P2 Pin Name P2 ADC M-SoM Pin M-SoM Pin Name M-SoM ADC
A0 / D11 23 A0 / D19
A1 / D12 33 A1 / D18
A2 / D13 35 A2 / D17
A5 / D14 43 A5 / D14
    53 A5 / D14
    45 A6 / D29
    47 A7 / WKP
D0 / A3 22 D0  
D1 / A4 20 D1  
S0 / D15   41 A4 / D15
S1 / D16   37 A3 / D16
S2 / D17   35 A2 / D17
S3 / D18   33 A1 / D18
S4 / D19   23 A0 / D19
  • 6 ADC on the M-SoM vs. 6 on the P2
  • On the P2, 2 of the ADCs are on the same pins as I2C
  • ADC inputs are single-ended and limited to 0 to 3.3V on both
  • Resolution is 12 bits on both
  • SoM pin 45 (A6) on the M-SoM is shared with SoM pin 53 (SWD_CLK). You cannot use A6 and SWD at the same time. If you implement SWD on your base board, driving pin A6 will prevent SWD from functioning. The SWD_CLK will be driven at hoot by the MCU.
  • On the P2, VBAT_MEAS is a 5V tolerant ADC for measuring battery voltage. This is not present on the M-SoM as typically you will use a fuel gauge chip instead of the less accurate voltage measurement to measure battery SoC.
  • ADC input A7 has a low impedance which may be an issue when supplied from a voltage divider. The other ADC inputs are comparable to the P2/Photon 2.

Serial

P2 Pin Name P2 Serial M-SoM Pin M-SoM Pin Name M-SoM Serial
D10 / WKP Serial3 (CTS) 38 RX / D10 Serial1 (RX)
S0 / D15 Serial3 (TX) 41 A4 / D15  
S1 / D16 Serial3 (RX) 37 A3 / D16  
S2 / D17 Serial3 (RTS) 35 A2 / D17  
D2 Serial2 (RTS) 42 D2 Serial1 (RTS)
    58 D24 Serial2 (TX)
    60 D25 Serial2 (RX)
D3 Serial2 (CTS) 40 D3 Serial1 (CTS)
D4 Serial2 (TX) 66 D4  
D5 Serial2 (RX) 68 D5  
RX / D9 Serial1 (RX) 36 TX / D9 Serial1 (TX)
TX / D8 Serial1 (TX) 36 TX / D9 Serial1 (TX)
  • The P2 has a third UART serial port; this does not exist on M-SoM

SPI

P2 Pin Name P2 SPI M-SoM Pin M-SoM Pin Name M-SoM SPI
D10 / WKP   38 RX / D10 SPI1 (MISO)
S0 / D15 SPI (MOSI) 41 A4 / D15  
S1 / D16 SPI (MISO) 37 A3 / D16  
S2 / D17 SPI (SCK) 35 A2 / D17  
S3 / D18 SPI (SS) 33 A1 / D18  
D2 SPI1 (MOSI) 42 D2 SPI1 (SCK)
D3 SPI1 (MISO) 40 D3 SPI1 (SS)
D4 SPI1 (SCK) 66 D4  
D5 SPI1 (SS) 68 D5  
    48 D8 SPI (SS)
RX / D9   36 TX / D9 SPI1 (MOSI)
    50 MISO / D11 SPI (MISO)
    52 MOSI / D12 SPI (MOSI)
    54 SCK / D13 SPI (SCK)
TX / D8   36 TX / D9 SPI1 (MOSI)
  • Two SPI interfaces on both

I2C

P2 Pin Name P2 I2C M-SoM Pin M-SoM Pin Name M-SoM I2C
D0 / A3 Wire (SDA) 22 D0 Wire (SDA)
D1 / A4 Wire (SCL) 20 D1 Wire (SCL)
  • 1 I2C on both
  • 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

P2 Pin Name P2 PWM M-SoM Pin M-SoM Pin Name M-SoM PWM
A0 / D11   23 A0 / D19
A1 / D12   33 A1 / D18
A2 / D13 35 A2 / D17  
A5 / D14 43 A5 / D14
    53 A5 / D14
    45 A6 / D29
D1 / A4 20 D1  
D10 / WKP   38 RX / D10
S0 / D15 41 A4 / D15  
S1 / D16 37 A3 / D16  
S3 / D18   33 A1 / D18
S4 / D19   23 A0 / D19
D4   66 D4
D5   68 D5
D6   70 D6
D7   72 D7
RX / D9   36 TX / D9
    50 MISO / D11
    52 MOSI / D12
TX / D8   36 TX / D9
  • PWM pins vary between the P2 and M-SoM

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]

Sleep

  • In HIBERNATE sleep mode, the M-SoM and P2 can only be wakened via the WKP pin, however WKP is pin A7 the M-SoM (and B-SoM) but is pin D10 on the P2.

  • In HIBERNATE sleep mode, certain pins on the M-SoM and P2 do not preserve INPUT_PULLUP or INPUT_PULLDOWN while asleep. See details below.

M-SoM pins related to HIBERNATE sleep mode:

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]

P2 pins related to HIBERNATE sleep mode:

Pin Pin Name Description Interface MCU
30 D10 / WKP D10 GPIO, Serial 3 CTS, WKP. (Was WKP/A7 on P1.) Only this pin can wake from HIBERNATE sleep mode. PA[15]
33 S6 / D21 S6 GPIO. (Was P1S6/TESTMODE on P1.) No internal pull up or pull down in HIBERNATE sleep mode. PB[31]
47 S4 / D19 S4 GPIO. (Was P1S4 on P1.) No internal pull up or pull down in HIBERNATE sleep mode. PA[0]
48 S5 / D20 S5 GPIO. (Was P1S5 on P1.) No internal pull up or pull down in HIBERNATE sleep mode. PB[29]

Full comparison

3V3

P2 M-SoM
  Pin Name 3V3 3V3
Description 3.3V power to MCU System power in, supply a fixed 3.3V power, 500 mA minimum

3V3_IO

Removed from P2
Pin Name 3V3_IO
Description 3.3V power to MCU IO.

3V3_RF

Removed from P2
Pin Name 3V3_RF
Description 3.3V power to RF module

A0

P2 M-SoM
  Pin Name A0 A0
Pin Alternate Name D11 D19
Description A0 Analog in, GPIO A0 Analog in, GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K 42K

A1

P2 M-SoM
  Pin Name A1 A1
Pin Alternate Name D12 D18
Description A1 Analog in, GPIO A1 Analog in, GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K ???

A2

P2 M-SoM
  Pin Name A2 A2
Pin Alternate Name D13 D17
Description A2 Analog in, PWM, GPIO A2 Analog in, GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports analogRead Yes Yes
Supports analogWrite (PWM) Yes No
Supports tone Yes No
  Supports attachInterrupt Yes Yes
Internal pull resistance 42K 22K

A5

P2 M-SoM
  Pin Name A5 A5
  Pin Alternate Name D14 D14
Description A5 Analog in, GPIO, PWM. 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 Yes Yes
  Supports attachInterrupt Yes Yes
Internal pull resistance 42K ???
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 ???

A7

Added to M-SoM
Pin Name A7
Pin Alternate Name WKP
Description A7 Analog In, WKP, GPIO D28
Supports digitalRead Yes
Supports digitalWrite Yes
Supports analogRead 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

P2 M-SoM
  Pin Name D0 D0
Pin Alternate Name A3 n/a
Description D0 GPIO, I2C SDA, A3 Analog In D0 GPIO, I2C SDA
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead Yes No
  I2C interface SDA. Use Wire object. Use 1.5K to 10K external pull-up resistor. SDA. Use Wire object. Use 1.5K to 10K external pull-up resistor.
  Supports attachInterrupt Yes Yes
Internal pull resistance 22K ???

D1

P2 M-SoM
  Pin Name D1 D1
Pin Alternate Name A4 n/a
Description D1 GPIO, PWM, I2C SCL, A4 Analog In D1 GPIO, I2C SCL
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead Yes No
Supports analogWrite (PWM) Yes No
Supports tone Yes No
  I2C interface SCL. Use Wire object. Use 1.5K to 10K external pull-up resistor. SCL. Use Wire object. Use 1.5K to 10K external pull-up resistor.
  Supports attachInterrupt Yes Yes
Internal pull resistance 22K ???

D10

P2 M-SoM
Pin Name D10 RX
Pin Alternate Name WKP D10
Description D10 GPIO, Serial 3 CTS, WKP. (Was WKP/A7 on P1.) 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 CTS. Use Serial3 object. Flow control optional. RX. Use Serial1 object.
SPI interface n/a MISO. Use SPI1 object.
  Supports attachInterrupt Yes Yes
  Internal pull resistance 2.1K 2.1K

D15

P2 M-SoM
Pin Name S0 A4
  Pin Alternate Name D15 D15
Description S0 GPIO, PWM, SPI MOSI, Serial3 TX. (Was P1S0 on P1.) A4 Analog in, GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead No Yes
Supports analogWrite (PWM) Yes No
Supports tone Yes No
UART serial TX. Use Serial3 object. n/a
SPI interface MOSI. Use SPI object. n/a
  Supports attachInterrupt Yes Yes
  Internal pull resistance 2.1K 2.1K

D16

P2 M-SoM
Pin Name S1 A3
  Pin Alternate Name D16 D16
Description S1 GPIO, PWM, SPI MISO, Serial3 RX. (Was P1S1 on P1.) A3 Analog in, GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead No Yes
Supports analogWrite (PWM) Yes No
Supports tone Yes No
UART serial RX. Use Serial3 object. n/a
SPI interface MISO. Use SPI object. n/a
  Supports attachInterrupt Yes Yes
  Internal pull resistance 2.1K 2.1K

D17

P2 M-SoM
Pin Name S2 A2
  Pin Alternate Name D17 D17
Description S2 GPIO, SPI SCK, Serial3 RTS. (Was P1S2 on P1.) A2 Analog in, GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead No Yes
UART serial RTS. Use Serial3 object. Flow control optional. n/a
SPI interface SCK. Use SPI object. n/a
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K 22K

D18

P2 M-SoM
Pin Name S3 A1
  Pin Alternate Name D18 D18
Description S3 GPIO. (Was P1S3 on P1.), SPI SS A1 Analog in, GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead No Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
SPI interface Default SS for SPI. n/a
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K ???

D19

P2 M-SoM
Pin Name S4 A0
  Pin Alternate Name D19 D19
Description S4 GPIO. (Was P1S4 on P1.) A0 Analog in, GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogRead No Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  Supports attachInterrupt Yes Yes
Internal pull resistance 22K. No internal pull up or pull down in HIBERNATE sleep mode. 42K

D2

P2 M-SoM
  Pin Name D2 D2
Description D2 GPIO, Serial2 RTS, SPI1 MOSI D2 GPIO, Serial RTS flow control (optional), SPI1 SCK
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
UART serial RTS. Use Serial2 object. Flow control optional. RTS. Use Serial1 object.
SPI interface MOSI. Use SPI1 object. SCK. Use SPI1 object.
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K ???

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

P2 M-SoM
  Pin Name D3 D3
Description D3 GPIO, Serial2 CTS, SPI1 MISO D3 GPIO, Serial1 CTS flow control (optional), SPI1 SS
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
UART serial CTS. Use Serial2 object. Flow control optional. CTS. Use Serial1 object.
SPI interface MISO. Use SPI1 object. SS. Use SPI1 object.
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K ???

D4

P2 M-SoM
  Pin Name D4 D4
Description D4 GPIO, Serial2 TX, SPI1 SCK D4 GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
UART serial TX. Use Serial2 object. n/a
SPI interface SCK. Use SPI1 object. n/a
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K ???

D5

P2 M-SoM
  Pin Name D5 D5
Description D5 GPIO, Serial2 RX, SPI1 SS D5 GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
UART serial RX. Use Serial2 object. n/a
SPI interface SS. Use SPI1 object. Can use any pin for SPI1 SS/CS however. n/a
  Supports attachInterrupt Yes Yes
Internal pull resistance 2.1K ???

D6

P2 M-SoM
  Pin Name D6 D6
Description D6 GPIO, SWCLK D6 GPIO, PWM
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  Supports attachInterrupt Yes Yes
Internal pull resistance 42K ???
SWD interface SWCLK. 40K pull-down at boot. n/a
Signal used at boot SWCLK. 40K pull-down at boot. n/a

D7

P2 M-SoM
  Pin Name D7 D7
Description D7 GPIO, SWDIO D7 GPIO, PWM
Supports digitalRead Yes. Yes
Supports digitalWrite Yes. On the Photon this is the blue D7 LED. Yes
Supports analogWrite (PWM) No Yes
Supports tone No Yes
  Supports attachInterrupt Yes Yes
Internal pull resistance 42K ???
SWD interface SWDIO. 40K pull-up at boot. n/a
Signal used at boot SWDIO. 40K pull-up at boot. Low at boot triggers MCU test mode. n/a

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

D9

P2 M-SoM
Pin Name RX TX
  Pin Alternate Name D9 D9
Description Serial1 RX (received data), 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 RX. Use Serial1 object. TX. Use Serial1 object.
SPI interface n/a MOSI. Use SPI1 object.
  Supports attachInterrupt Yes Yes
Internal pull resistance 42K 2.1K

GND

P2 M-SoM
  Pin Name GND GND
Description Ground. Be sure you connect all P1 ground pins. Ground.

GNSS_TX

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

MISO

Added to M-SoM
Pin Name MISO
Pin Alternate Name D11
Description D11 GPIO, PWM, SPI MISO
Supports digitalRead Yes
Supports digitalWrite Yes
Supports analogWrite (PWM) Yes
Supports tone Yes
SPI interface MISO. Use SPI object.
Supports attachInterrupt Yes
Internal pull resistance 2.1K

MODE

Unchanged between P2 and M-SoM
Pin Name MODE
Description MODE button. Pin number constant is BTN. External pull-up required!
Supports attachInterrupt Yes

MOSI

Added to M-SoM
Pin Name MOSI
Pin Alternate Name D12
Description D12 GPIO, PWM, SPI MOSI
Supports digitalRead Yes
Supports digitalWrite Yes
Supports analogWrite (PWM) Yes
Supports tone Yes
SPI interface MOSI. Use SPI object.
Supports attachInterrupt Yes
Internal pull resistance 2.1K

NC

P2 M-SoM
  Pin Name NC NC
Description No connection. Do not connect anything to this pin. n/a

RGBB

P2 M-SoM
  Pin Name RGBB RGBB
  Description RGB LED Blue RGB LED Blue
Supports attachInterrupt Yes No

RGBG

P2 M-SoM
  Pin Name RGBG RGBG
  Description RGB LED Green RGB LED Green
Supports attachInterrupt Yes No

RGBR

P2 M-SoM
  Pin Name RGBR RGBR
Description RGB LED Red. Has 10K hardware pull-up. Do not hold low at boot. RGB LED Red
Supports attachInterrupt Yes No
Signal used at boot n/a Low at boot triggers trap mode

RST

P2 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.

S5

P2 M-SoM
Pin Name S5 D20
Pin Alternate Name D20 n/a
Description S5 GPIO. (Was P1S5 on P1.) D20 GPIO
Supports digitalRead No Yes
  Supports digitalWrite Yes Yes
  Supports attachInterrupt Yes Yes
Internal pull resistance 22K. No internal pull up or pull down in HIBERNATE sleep mode ???

S6

P2 M-SoM
Pin Name S6 D21
Pin Alternate Name D21 n/a
Description S6 GPIO. (Was P1S6/TESTMODE on P1.) D21 GPIO
  Supports digitalRead Yes Yes
  Supports digitalWrite Yes Yes
  Supports attachInterrupt Yes Yes
  Internal pull resistance 22K. No internal pull up or pull down in HIBERNATE sleep mode. 22K. No internal pull up or pull down in HIBERNATE sleep mode.

SCK

Added to M-SoM
Pin Name SCK
Pin Alternate Name D13
Description D13 GPIO, SPI SCK
Supports digitalRead Yes
Supports digitalWrite Yes
SPI interface SCK. Use SPI object.
Supports attachInterrupt Yes
Internal pull resistance 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

P2 M-SoM
  Pin Name TX TX
Pin Alternate Name D8 D9
Description Serial1 TX (transmitted data), 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 Yes
Internal pull resistance 42K 2.1K
Signal used at boot Low at boot triggers ISP flash download n/a

USBDATA-

Unchanged between P2 and M-SoM
Pin Name USBDATA-
Description USB Data-
Input is 5V Tolerant Yes

USBDATA+

Unchanged between P2 and M-SoM
Pin Name USBDATA+
Description USB Data+
Input is 5V Tolerant Yes

VBAT_MEAS

Removed from P2
Pin Name VBAT_MEAS
Description Battery voltage measurement (optional).
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.

Software

Wi-Fi configuration

Wi-Fi setup works the same as the P2, Photon 2, and Argon, and uses BLE. See Wi-Fi setup options for more information.

Platform ID

The Platform ID of the msom (35, PLATFORM_MSOM) is different from that of the P2 (32) because of the different hardware.

If you have a product based on the P2, 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 between the P2 and M-SoM as they share a similar MCU. The exceptions include:

  • Libraries that are hardcoded to support only certain platforms by their PLATFORM_ID

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