P2 from P1 migration guide

The Particle P2 module is the next generation Wi-Fi module from Particle. It is footprint compatible with our prior module, the P1, but is built on an upgraded chipset, supporting advanced features such as 5 GHz Wi-Fi, a 200MHz CPU, and built-in Bluetooth BLE 5.0.

¹A small amount of the flash file system is used by Device OS, most is available for user data storage using the POSIX filesystem API. This is separate from the flash memory used for Device OS, user application, and OTA transfers.

² Total RAM; amount available to user applications is smaller. On the P2, available RAM is approximately 3072 KB. On the P1, it is 55 KB.

³ Total built-in flash; amount available to user applications is smaller. The Argon also has a 4 MB external flash, a portion of which is available to user applications as a flash file system.

⁴ Onboard or external antenna is selectable in software.

Hardware

No 5V tolerance!

On Gen 2 devices (STM32F205), most pins are 5V tolerant. This is not the case for Gen 3 (nRF52840) and the P2 (RTL872x). You must not exceed 3.3V on any GPIO pin, including ports such as serial, I2C, and SPI.

Pins A3, A4, and DAC (A6)

Pins A3 (module pin 22), A4 (module pin 21), DAC/A6 (module pin 24) do not exist on the P2 and are NC.

You will need to use different pins if you are currently using these pins.

SPI

Both the P1 and P2 have two SPI ports, however the pins are different for SPI (primary SPI).

The following are all SPI-related pins on the P1 and P2:

If you are using SPI, Device OS 5.3.1 or later is recommended. Prior to that version, SPI ran at half of the set speed, and SPI1 ran at double the set speed. Timing has also been improved for large DMA transfers; prior to 5.3.1, there could be 1 µs gaps for every 16 bytes of data transferred.

SPI - Gen 2 devices (including P1)

• Available clock divisors: 2, 4, 8, 16, 32, 64, 128, 256

SPI - P2

I2C

The P2 supports one I2C (two-wire serial interface) port on the same pins as the P1:

• The P2 I2C port is not 5V tolerant
• The P1 includes internal 2.2K pull-up resistors on D0/D1, the P2 does not
• On the 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.

Serial (UART)

The primary UART serial (Serial1) is on the TX and RX pins on both the P1 and P2. There is no hardware flow control on this port on the P1 or P2.

The secondary UART serial (Serial2) is on different pins, however it does not conflict with the RGB LED, and also supports CTS/RTS hardware flow control.

There is also a third UART serial (Serial3).

¹CTS/RTS flow control only on Serial2. It is optional.

Supported Baud Rates:

Analog input (ADC)

For analog to digital conversion (ADC) using analogRead(), there are fewer ADC inputs on the P2:

On the P2, there are no pins A3 (hardware pin 21) and A4 (hardware pin 22); these are NC (no connection). However, P2 pin D0 (hardware pin 36) can be used as an analog input and has the alias A3. The same is true for P2 pin D1 (hardware pin 35), which has the alias A4.

The setADCSampleTime() function is not supported on the P2.

PWM (Pulse-width modulation)

The pins that support PWM are different on the P1 and P2.

All available PWM pins on the P2 share a single timer. This means that they must all share a single frequency, but can have different duty cycles.

Digital to analog converter (DAC)

The P1 supports DAC one A3 and A6 (DAC). There is no DAC on the P2 or Gen 3 devices.

If you need a DAC, it's easy to add one via I2C or SPI on your base board.

WKP (A7)

On Gen 2 devices (STM32), only the WKP pin can wake from HIBERNATE sleep mode.

This restriction does not exist on the P2 and Gen 3 devices; any pin can be used to wake from all sleep modes.

CAN (controller area network)

The P1 supports CAN on pins D1 and D2. There is no CAN on the P2 or Gen 3 devices (except the Tracker).

• The Tracker SoM includes CAN via a MCP25625 CAN interface with integrated transceiver.
• Both the MCP2515 and MCP25625 work with the library used on the Tracker and can be used to add CAN to the P2.

I2S (Sound)

The P1 theoretically had I2S sound available on pins D1 and D2, however there has never been support for it in Device OS.

There is no software support for I2S on the P2 either, and while the RTL872x hardware supports I2S, the pins that it requires are in use by other ports.

BLE (Bluetooth LE)

BLE Central Mode on the P2 and Photon 2 is only supported in Device OS 5.1.0 and later. Earlier versions only supported BLE Peripheral Mode.

Sleep

The P2 can wake from STOP or ULTRA_LOW_POWER sleep mode on any GPIO, RISING, FALLING, or CHANGE.

The P2 can only wake from HIBERNATE sleep mode on pin D10, RISING, FALLING, or CHANGE. Pin D10 is the same module pin location (pin 30) as the P1 WKP (A7) pin, and the STM32 can only wake from HIBERNATE on WKP RISING so this should not be an issue.

Internal pull-up or pull-down

Internal (MCU) pull-up and pull-down can be enabled using the pinMode() function and INPUT_PULLUP or INPUT_PULLDOWN.

• On the P2, the internal pull varies by pin and can be approximately 2.1K, 22K, or 42K.
• On the P1, the internal pull is approximately 40K.

MODE button

The P2 MODE button does not have a hardware pull-up on it, so you must add an external pull-up (2.2K to 10K) to 3V3, or connect it to 3V3 if not using a button.

The P1 had an internal weak pull-up.

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.

Interrupts

There are many limitations for interrupts on the STM32F205. All pins can be used for interrupts on Gen 3 devices and the P2.

Internal pull-up or pull-down

Internal (MCU) pull-up and pull-down can be enabled using the pinMode() function and INPUT_PULLUP or INPUT_PULLDOWN.

• On the P2, the internal pull varies by pin and can be approximately 2.1K, 22K, or 42K.
  • Pins A0, A1, D2, D3, D4, D5, D10, S0, S1, S2 are 2.1K
  • Pins D0, D1, S4, S5, S6 are 22K
  • Pins A2, A5, D6, TX, RX are 42K
  • Pins S4, S5, S6 do not support pull-up or pull-down in HIBERNATE sleep mode. Use an external pull resistor if this is required.
• On the P1, the internal pull is approximately 40K.
• The P1 module has 2.1K pull-ups on D0 and D1 (I2C), separate from the MCU pull-ups. The P2 does not have extra hardware pull-ups.

Retained memory

The P2 and Photon 2 have limited support for retained memory, also referred to as Backup RAM or SRAM, in Device OS 5.3.1 and later.

Retained memory is preserved with the following limitations:

• When entering HIBERNATE sleep mode.
• Under programmatic reset, such as System.reset() and OTA firmware upgrades.
• In limited cases when using pin reset (RESET button or externally triggered reset).

By default, the retained memory is saved every 10 seconds, so changes made to retained variables between the last save and an unplanned system reset will be lost. Calling System.backupRamSync on the P2 and Photon 2 can make sure the data is saved. The data is saved to a dedicated flash page in the RTL827x MCU however you should avoid saving the data extremely frequently as it is slower than RAM and will cause flash wear.

Prior to Device OS 5.3.1, retained memory is not supported. The flash file system can be used, or you can use an external chip such as an I2C or SPI FRAM.

Retained memory is 3068 bytes.

Flash file system

The P1 did not have a flash file system.

The P2 has a 2 MB flash file system using the same POSIX API as Gen 3 devices. A small amount of space is reserved for system use including configuration data. Most of the space is available for user application use.

EEPROM

The EEPROM emulation API is the same across the P1 and P2.

The P1 had 2047 bytes of emulated EEPROM. The P2 has 4096 bytes of emulated EEPROM. On the P2 and Gen 3 devices, the EEPROM is actually just a file on the flash file system.

Pin functions removed

The following pins served P1-specific uses and are NC on the P2. You should not connect anything to these pins.

Pin functions added

The following pins were NC on the P1 but are used on the P2.

Full module pin comparison

Module Pin 1 (GND)

Module Pin 2 (VBAT_WL / 3V3_RF)

Module Pin 3 (VBAT_WL / 3V3_RF)

Module Pin 4 (GND)

Module Pin 5 (VDDIO_3V3_WL / 3V3_IO)

Module Pin 6 (GND)

Module Pin 7 (WL_REG_ON / NC)

Module Pin 8 (NC)

Module Pin 9 (NC)

Module Pin 10 (NC)

Module Pin 11 (NC)

Module Pin 12 (NC / VBAT_MEAS)

Module Pin 13 (GND)

Module Pin 14 (NC)

Module Pin 15 (GND)

Module Pin 16 (WL_JTAG_TDI / NC)

Module Pin 17 (WL_JTAG_TCK / NC)

Module Pin 18 (WL_JTAG_TRSTN / NC)

Module Pin 19 (WL_JTAG_TMS / NC)

Module Pin 20 (WL_JTAG_TDO / NC)

Module Pin 21 (A4 / NC)

Module Pin 22 (A3 / NC)

Module Pin 23 (A5)

Module Pin 24 (DAC / NC)

Module Pin 25 (GND)

Module Pin 26 (3V3)

Module Pin 27 (3V3)

Module Pin 28 (GND)

Module Pin 29 (RGBR)

Module Pin 30 (WKP / D10)

Module Pin 31 (RGBB)

Module Pin 32 (RGBG)

Module Pin 33 (P1S6 / S6)

Module Pin 34 (RST)

Module Pin 35 (D1)

Module Pin 36 (D0)

Module Pin 37 (GND)

Module Pin 38 (VBAT / NC)

Module Pin 39 (GND)

Module Pin 40 (P1S0 / S0)

Module Pin 41 (P1S1 / S1)

Module Pin 42 (P1S2 / S2)

Module Pin 43 (A1)

Module Pin 44 (P1S3 / S3)

Module Pin 45 (D2)

Module Pin 46 (MODE)

Module Pin 47 (P1S4 / S4)

Module Pin 48 (P1S5 / S5)

Module Pin 49 (A2)

Module Pin 50 (A0)

Module Pin 51 (D3)

Module Pin 52 (D4)

Module Pin 53 (D5)

Module Pin 54 (D7)

Module Pin 55 (D6)

Module Pin 56 (BTCX_STATUS / NC)

Module Pin 57 (BTCX_RF_ACTIVE / NC)

Module Pin 58 (BTCX_TXCONF / NC)

Module Pin 59 (GND)

Module Pin 60 (WL_SLEEP_CLK / NC)

Module Pin 61 (USBDATA+)

Module Pin 62 (USBDATA-)

Module Pin 63 (RX)

Module Pin 64 (TX)

Module Pin 65 (GND)

Module Pin 66 (GND)

Module Pin 67 (GND)

Module Pin 68 (GND)

Module Pin 69 (GND)

Module Pin 70 (GND)

Module Pin 71 (GND)

Module Pin 72 (GND)

Software

Wi-Fi Configuration

The P2 and Argon utilize BLE or USB for configuration of Wi-Fi rather than the SoftAP approach taken with the P1. Using BLE allow mobile apps to more easily set up the device Wi-Fi without having to modify the mobile device's network configuration.

Sample applications for React Native, iOS, and Android will be provided in the future.

User firmware binary size

One major advantage of the P2 is that user firmware binaries can be up to 2048 Kbytes, instead of 128 Kbytes on Gen 2 devices including the P1.

Flash file system

On the P2 there is a flash file system (2 MB) for storing user data. This is not available on Gen 2 devices including the P1.

Combined and resumable OTA

On the P2, over-the-air (OTA) updates have two features that can improve the speed and reliability of OTA updates:

• Combined OTA can combine Device OS and user firmware updates into a single binary that requires only one download and one reboot to install.
• Resumable OTA allows an update to resume from the point it stopped, instead of starting over from the beginning if interrupted.

Increased API field limits

The maximum size of a variable, function parameter, or publish is 1024 bytes on the P2 vs. 864 bytes on P1.

Platform ID

The Platform ID of the P2 (32, PLATFORM_P2) is different from that of the P1 (8) because of the vastly different hardware.

If you have a product based on the P1, you will need to create a separate product for devices using the P2. 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

Version history