B-Series from Boron Migration Guide

The B-Series SoM (system-on-a-module) is similar to the Boron in that it is a 3rd-generation cellular device. It plugs into an M.2 NGFF connector on your custom circuit board and is intended for mass production use.

Many of the extra features on the Boron have been omitted from the SoM, so you can implement a custom solution as necessary. For example, rather than duplicating the buttons and status LED on the SoM, you can put them on an external control panel for your product, or omit them entirely.

Additionally, the extra width vs. the Boron (Adafruit Feather) form-factor makes it possible to include a LTE Cat 1 with 2G/3G fallback cellular modem, such as the Quectel EG91-E on the B524. This modem is too wide to fit on a Boron.

¹The PMIC (power management IC) and fuel gauge are used with battery-powered applications. They're omitted from the SoM as they are not needed for externally powered solutions (grid or automotive power, for example). Additionally, you may want to use different models if you are making a solar-powered device, or using a different battery technology or multiple battery pack.

²The built-in Particle SIM card is free for use up to certain limits, no credit card required.

The available models include:

• The B404X, B404, and B402 cannot be used in Central or South America.
• The B524 can be used in selected countries in Europe, Middle East, Africa, and Asia (EMEAA), including Australia and New Zealand.
• The B524 and B523 do not work out of the EMEAA region.
• See the Carrier List for compatibility in specific countries

Datasheets

• B404X datasheet
• B524/B523 datasheet
• B-Series evaluation board

If you want to migrate from the Electron or E-Series to the B-Series SoM, see Gen 2 cellular migration.

Countries - B404X, B404

Countries - B524

SKUs

• EMEAA: Selected countries in Europe, Middle East, Africa, and Asia, including Australia and New Zealand. See the cellular carrier list for more information.

Prototyping

The B-Series SoM cannot be used without a base board. Typically you will create your own board, however there are two off-the-shelf options available:

B-Series Eval board

The B-Series evaluation board provides a variety of interfaces and access to all ports and pins on the B-Series SoM. You can use the expansion connector to connect the evaluation board to a breadboard for prototyping. You can also add sensors and accessories using the Grove expansion connectors.

Mikroe Gen 3 SoM shield

The Gen 3 SoM shield connects a B-Series SoM to mikroBUS Click boards:

There is a huge library of mikroBUS Click expansion boards, however the caveat is that most of them do not already have a Particle software library. If the board is for a common sensor or chip, however, existing Particle libraries for the chip will typically work, even if not designed work with the Click.

For more information, see the Mikroe community page.

Creating a board

First SoM board tutorial

The SoM first board tutorial shows how to get started with the M.2 SoM boards by making the simplest possible design. It's an introduction to working with surface mount components you will need in order to make your own SoM base board.

Basic SoM design

This design is a bit more complicated, and includes the PMIC and Fuel Gauge chips that are present on the Boron:

• RGB LED
• bq24195 PMIC
• MAX17043 Fuel Gauge
• USB Connector
• LiPo Connector (JST-PH)
• M.2 SoM Connector

This is the basic set of features you'll probably want to include in a LiPo battery-powered design. The Evaluation Board is also a good reference to use. This design, however, is simple enough that it can be hand-assembled, though you still need a reflow oven and some of the parts (in particular the fuel gauge and PMIC) are tiny and there are a lot of them.

This board a two-layer circuit board so it can be manufactured inexpensively and edited using the free version of Eagle CAD.

As this board doesn't really do much, you'll unlikely use it as-is, but you can use it as a tutorial for how to hook up the PMIC and fuel gauge.

Hardware differences

Antennas

The Boron has a built-in BLE chip antenna, antenna switch, and U.FL antenna connector. The B-Series SoM only has a U.FL connector for BLE and does not have a built-in antenna.

Both require an external cellular antenna.

Both require an external antenna for NFC tag.

SPI

SPI is mostly unchanged between the Boron and B-Series SoM. The only difference is the default SS pin, however you can choose any GPIO for your SPI chip select, you do not need to use the default.

Serial (UART)

Hardware serial (UART) ports are unchanged between the Boron and B-Series SoM.

Analog input (ADC)

There are two additional ADC inputs on the B-Series SoM. These can also be used as digital GPIO.

PWM (Pulse-width modulation)

These are differences in pins that support PWM between the Boron and B-Series SoM.

Interrupts

All pins can be used for interrupts on Gen 3 devices, however only 8 pins can be used for interrupts at the same time.

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 both the Boron and B-Series SoM (Gen 3), the internal pull is approximately 16K.

Retained memory

Retained memory, also referred to as Backup RAM or SRAM, that is preserved across device reset.

On both the Boron and B-Series SoM, retained memory is 3068 bytes.

The flash file system on Gen 3 devices can also be used for data storage, however care must be taken to avoid excessive wear of the flash for frequently changing data.

USB

The Boron has a Micro USB B connector.

The B-Series SoM does not have a USB connector. It is recommended that you add one to your base board for programming and troubleshooting/

NFC tag

The Boron and B-Series SoM have NFC Tag support.

The Boron has a U.FL connector on the bottom of the board; you must supply your own NFC antenna connector or integrated antenna on your base board.

PMIC Notes

When using the B-Series SoM with a bq24195 PMIC, note the following:

By default, the bq24195 sets the input current limit, which affects powering by VIN and VUSB, to 100 mA. This affects the VSYS output of the PMIC, which powers both the cellular modem and 3V3 supply, and is not enough to power the B-Series SoM in normal operation.

If your device has the default firmware (Tinker), it will attempt to connect to the cloud, brown out due to insufficient current, then the device will reset. This may result in what appears to be the status LED blinking white, but is actually rolling reboot caused by brownout.

A factory new B-Series SoM does not enable the PMIC setup. To enable the use of the bq21415, you must enable the system power feature PMIC_DETECTION in your code. This defaults to off because the B-Series SoM can be used without a PMIC, or with a different PMIC, and also requires I2C on D0/D1, and some base boards may use those pins as GPIO.

Because the input current limit does not affect the battery input (Li+), for troubleshooting purposes it can be helpful to attach a battery to help rule out input current limit issues. It's also possible to supply 3.7V via a bench power supply to the battery input, instead of VIN.

The input current limit can result in a situation where you can't bring up a B-Series SoM because it browns out continuously, but also cannot flash code to it to stop if from browning out. There are two general solutions:

• Attach a battery or supply by Li+ when bringing up a board.
• Use SWD/JTAG and reset halt the MCU. This will prevent it from connecting to the cloud, so you can flash Device OS and firmware to it by SWD.

The input current limit is actually controlled by three factors:

• The power source max current setting in the PMIC. The default is 900 mA. It can be set to 100, 150, 500, 900, 1200, 1500, 2000, or 3000 mA.
• It is also limited by the hardware ILIM resistor. On Particle devices with a built-in PMIC, this is set to 1590 mA, but if you are implementing your own PMIC hardware, you can adjust this higher.
• When connected by USB, it will use DPDM, current negotiation via the USB DP (D+) and DM (D-) lines.

Note that some 2A tablet chargers and multi-port USB power supplies supply 2A but do not implement DPDM; these will be treated as if VIN was used, and you must set the power source current, otherwise the input current will be limited to 900 mA, which is not enough to power a 2G/3G cellular modem without an attached battery.

Full module pin comparison

3V3

A0

A1

A2

A3

A4

A5

A6

A7

AGND

CELL USBD-

CELL USBD+

CELL VBUS

D0

D1

D2

D22

D23

D3

D4

D5

D6

D7

D8

EN

GND

LI+

MISO

MODE

MOSI

NC

NC

NFC1

NFC2

RGBB

RGBG

RGBR

RST

RX

SCK

SIM_CLK

SIM_DATA

SIM_RST

SIM_VCC

TX

USBDATA-

USBDATA+

VCC

VUSB

Software

Platform ID

The platforms IDs of the B-Series SoM models vary from the Boron.

If you have a product based on the Boron, you will need to create a separate product (or two) for devices using the B-Series 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.

The reason there are separate platforms for the B4xx and B5xx SoM is that they have different cellular modem manufacturers, u-blox and Quectel, respectively. All Boron models have u-blox cellular modems and thus can share a single platform.

Third-party libraries

Most third-party libraries are believed to be compatible between the Boron and B-Series SoM.

Version history