Electron Datasheet

Functional description

Overview

Note: The Electron U260 and U270 have been deprecated and are no longer available for sale. New designs should use the B-Series SoM or Boron. For a pin-compatible replacement for the G350, U260, and U270, the Electron ELC314 is available in tray quantities only.

The Electron is a tiny development kit for creating cellular-connected electronics projects and products. It comes with a SIM card (Nano 4FF)^[1] and an affordable data plan for low-bandwidth things. Plus it's available for more than 100 countries worldwide!

It also comes with Particle's development tools and cloud platform for managing and interacting with your new connected hardware.

Features

• U-blox SARA-U201/U260/U270 (3G with 2G fallback), G350 (2G), or R410M (LTE Cat M1) cellular module
• STM32F205RGT6 120MHz ARM Cortex M3 microcontroller
• 1MB flash, 128KB RAM
• BQ24195 power management unit and battery charger
• MAX17043 fuel gauge
• RGB status LED
• 30 mixed-signal GPIO and advanced peripherals
• Open source design
• Real-time operation system (RTOS)
• FCC (United States), CE (European Union), and ISED (Canada) certified

^[1]The LTE model uses a MFF2 SMD Particle SIM instead of a physical SIM card. The Electron LTE is only available to existing enterprise customers who have deployed an Electron 2G/3G solution and would like to upgrade to LTE. It is only available in tray quantities. New designs should use the Boron LTE or B-Series B404 SoM. It can only be used in the United States, Canada, and Mexico at this time.

Device OS support

It is recommended that you use the latest version in the 2.x LTS release line with the all Electrons.

While the devices are compatible with older versions of Device OS and 3.x, these versions as past the end-of-support date and are not recommended for use in production. Only 2.x LTS remains in the Extended Support and Maintenance (ESM) window.

For information on upgrading Device OS, see Version information. For the latest version shipped from the factory, see Manufacturing firmware versions page. See also Long Term Support (LTS) releases.

Interfaces

Block diagram

Power

The Electron can be powered via the VIN (3.9V-12VDC) pin, the USB Micro B connector or a LiPo battery.

USB

Most USB ports can supply only a maximum of 500mA, but the u-Blox GSM module on the Electron alone can consume a peak of 800mA to 1800mA (2G/3G) or 490 mA (LTE) of current during transmission. In order to compensate of this deficit, one must connect the LiPo battery at all times when powering from a traditional USB port for 2G/3G. The Electron will intelligently source power from the USB most of the time and keep the battery charged. During peak current requirements, the additional power will be sourced from the battery. This reduces the charge-discharge cycle load on the battery, thus improving its longevity.

VIN

The input voltage range on VIN pin is 3.9VDC to 12VDC. When powering from the VIN pin alone, make sure that the power supply is rated at 10W (for example 5VDC at 2Amp). If the power source is unable to meet this requirement, you'll need connect the LiPo battery as well. An additional bulk capacitance of 470uF to 1000uF should be added to the VIN input when the LiPo Battery is disconnected. The amount of capacitance required will depend on the ability of the power supply to deliver peak currents to the cellular modem.

The Electron LTE (ELC404 & ELC402, LTE Cat 1) can be powered with as little as 550 mA at 5V.

LiPo Battery

When powered from a LiPo battery alone, the power management IC switches off the internal regulator and supplies power to the system directly from the battery. This reduces the conduction losses and maximizes battery run time. The battery provided with the Electron is a Lithium-Ion Polymer battery rated at 3.7VDC 1,800mAh. You can substitute this battery with another 3.7V LiPo with higher current rating. Remember to never exceed this voltage rating and always pay attention to the polarity of the connector.

Typical current consumption is around 180mA and up to 1.8A transients at 5VDC. In deep sleep mode, the quiescent current is 130uA (powered from the battery alone).

Li+

This pin is internally tied to the positive terminal of the LiPo battery connector. It is intentionally left unpopulated. Please note that an incorrect usage of this pin can render the Electron unusable.

Li+ pin serves two purposes. You can use this pin to connect a LiPo battery directly without having to use a JST connector or it can be used to connect an external DC power source (and this is where one needs to take extra precautions). When powering it from an external regulated DC source, the recommended input voltage range on this pin is between 3.6V to 4.4VDC. Make sure that the supply can handle currents of at least 2 Amps.

This is the most efficient way of powering the Electron since the PMIC by-passes the regulator and supplies power to the Electron via an internal FET leading to lower quiescent current.

VUSB

This pin is internally connected to USB supply rail and will output 5V when the Electron is plugged into an USB port. It is intentionally left unpopulated. This pin will NOT output any voltage when the Electron is powered via VIN and/or the LiPo battery.

3V3 Pin

This pin is the output of the on-board 3.3V switching regulator that powers the microcontroller and the peripherals. This pin can be used as a 3.3V power source with a max load of 800mA. 3.3V will also be available on that pin while the device being in deep sleep. Unlike the Photon or the Core, this pin CANNOT be used as an input to power the Electron.

VBAT

Supply to the internal RTC, backup registers and SRAM when 3V3 is not present (1.65 to 3.6VDC). The Pin is internally connected to 3V3 supply via a 0 ohm resistor. If you wish to power VBAT via an external supply, you'll need to remove this resistor with a desoldering iron. Contact us if you wish to request trays of electrons with this jumper depopulated.

Powering the Electron without a battery

The most forgiving way to power the Electron without a battery is via the VIN input see VIN above. Power may also be applied separately to the Li+ pin or LiPo JST connector see Li+ above.

FCC approved antennas

Peripherals and GPIO

Notes: ^[1] FT = 5.0V tolerant pins. All pins except A3 and DAC are 5V tolerant (when not in analog mode). If used as a 5V input the pull-up/pull-down resistor must be disabled.

^[2] 3V3 = 3.3V max pins.

^[3] PWM is available on D0, D1, D2, D3, B0, B1, B2, B3, A4, A5, WKP, RX, TX with a caveat: PWM timer peripheral is duplicated on two pins (A5/D2) and (A4/D3) for 11 total independent PWM outputs. For example: PWM may be used on A5 while D2 is used as a GPIO, or D2 as a PWM while A5 is used as an analog input. However A5 and D2 cannot be used as independently controlled PWM outputs at the same time.

^[4] Technically these pins are 5.0V tolerant, but since you wouldn't operate them with a 5.0V transceiver it's proper to classify them as 3.3V.

JTAG AND SWD

Pin D3 through D7 are JTAG interface pins. These can be used to reprogram your Electron bootloader or user firmware image with standard JTAG tools such as the ST-Link v2, J-Link, R-Link, OLIMEX ARM-USB-TINI-H, and also the FTDI-based Particle JTAG Programmer. If you are short on available pins, you may also use SWD mode which requires less connections.

Notes: [1] Default state after reset for a short period of time before these pins are restored to GPIO (if JTAG debugging is not required, i.e. USE_SWD_JTAG=y is not specified on the command line.)

Memory map

STM32F205RGT6 Flash layout overview

• Bootloader (16 KB)
• DCD1 (16 KB), stores keys, mfg info, system flags, etc..
• DCD2 (16 KB), swap area for DCD1
• EEPROM emulation bank 1 (16 KB)
• EEPROM emulation bank 2 (64 KB)
• Device OS (512 KB) [256 KB comms + 256 KB hal/platform/services]
• Factory backup, OTA backup and user application (384 KB) [3 x 128 KB]

DCD Layout

The DCD area of flash memory has been mapped to a separate DFU media device so that we can incrementally update the application data. This allows one item (say, server public key) to be updated without erasing the other items.

DCD layout in release/stable found here in firmware.

Memory map (common)

Memory map (modular firmware - default)

Before 0.6.0 firmware

Since 0.6.0 firmware

Memory map (monolithic firmware - optional)

Pin and button definition

Pin markings:

Pin description

Notes:

^[1] PWM is available on D0, D1, D2, D3, B0, B1, B2, B3, A4, A5, WKP, RX, TX with a caveat: PWM timer peripheral is duplicated on two pins (A5/D2) and (A4/D3) for 11 total independent PWM outputs. For example: PWM may be used on A5 while D2 is used as a GPIO, or D2 as a PWM while A5 is used as an analog input. However A5 and D2 cannot be used as independently controlled PWM outputs at the same time.

LED Status

Charge status LED

Notes:

^[1] A fault condition can occur due to several reasons, for example, battery over/under voltage, temperature fault or safety timer fault. You can find the root cause by reading the fault register of the power management IC in firmware.

^[2] You can stop this behavior by either plugging in the LiPo battery or by disabling charging using firmware command: PMIC().disableCharging();.

System RGB LED

For a detailed explanation of different color codes of the RGB system LED, please take a look here.

Pinout diagram

You can download a high resolution pinout diagram in a PDF version here.

Technical specifications

Absolute maximum ratings ^[1]

^[1] Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

Recommended operating conditions

Notes:

^[1] The minimum input voltage is software defined with a user selectable range of 3.88V to 5.08V in 80mV increments. Out of the box, the minimum input voltage is set to 4.36V in order for the LiPo battery to be able to properly charge.

^[2] 3G operation

^[3] 2G operation

Power consumption

¹The min, and particularly peak, values may consist of very short transients. The typical (typ) values are the best indicator of overall power consumption over time. The peak values indicate the absolute minimum capacity of the power supply necessary, not overall consumption.

Radio specifications

The Electron is available in different versions: A 2G version based on u-blox G350 cellular module, two 3G versions based on U260 and U270 modules, and a LTE Cat M1 model (R410M-02B-00 or R410M-02B-03).

Some countries have already stopped supporting 2G, including Australia, Japan, Korea, Singapore, and Taiwan. The cellular carrier used by the Electron no longer supports 2G in New Zealand and Switzerland. The G350 cannot be used in these countries.

The difference between the 3G versions is their operating frequency band which differs based on the country. All of these cellular modules are GSM only and do not support CDMA networks. Both 3G models can fall back to using 2G in areas that support 2G and not 3G.

Note that LTE is LTE Cat M1, not the standard LTE (LTE Cat 1) used by your mobile phone. It is a low-power and low-data-rate variation of LTE for use with IoT devices.

Please be sure to order a board that works in the country where you want to deploy your project.

2G cellular characteristics for G350, U201, U260, and U270 modules:

3G cellular characteristics for U201, U260, and U270 modules:

u-blox SARA-R410M-02B-00 or R410M-02B-03

I/O characteristics

These specifications are based on the STM32F205RGT6 datasheet, with reference to Electron pin nomenclature.

Notes:

_[1] FT = Five-volt tolerant. In order to sustain a voltage higher than V_3V3+0.3 the internal pull-up/pull-down resistors must be disabled.

_[2] Hysteresis voltage between Schmitt trigger switching levels. Based on characterization, not tested in production.

_[3] With a minimum of 100mV.

_[4] Leakage could be higher than max. if negative current is injected on adjacent pins.

_[5] Pull-up and pull-down resistors are designed with a true resistance in series with switchable PMOS/NMOS. This PMOS/NMOS contribution to the series resistance is minimum (~10% order).

Mechanical specifications

Dimensions and weight

• Width = 0.8"
• Height = 0.65"
• Length = 2.05"
• Weight = 10 grams

Mating connectors

The Electron can be mounted with (qty 2) 18-pin single row 0.1" female headers. Typically these are 0.335" (8.5mm) tall, but you may pick a taller one if desired. When you search for parts like these it can be difficult to navigate the thousands of parts available online so here are a few good choices for the Electron:

You may also use other types, such as reverse mounted (bottom side SMT) female headers, low profile types, etc..

Recommended PCB land pattern

The Electron can be mounted with 0.1" 18-pin female header receptacles using the following PCB land pattern:

An Electron part for EAGLE can be found in the Particle EAGLE library

Schematic

All of the Electron hardware design files are open source and available under a Creative Commons Public License. The schematic and PCB designs were made using EAGLE CAD. You can access these files here.

Note: Clone or Download the complete repository as a ZIP file to avoid corrupted data in Eagle files.

USB

The USB data lines are terminated with 22 Ohm resistors. These data pins are also exposed via small through holes next to the USB connector and are labeled D+ and D-. The VBUS (+5VDC VCC of the USB port) is fed to the PMIC via a 3Amp Schottky diode (SS3P3). The VBUS pin is also available via the unpopulated header hole on the top-right side of the Electron.

PMIC (Power Management integrated circuit)

The Electron uses TI's BQ24195 as the power management and charging unit. This PMIC intelligently sources power from either the VIN pin, the USB port and/or the LiPo battery. When all the power sources as connected, the unit tries to source power from the USB or VIN as default and continues to charge the LiPo battery. When the battery is completely charged, the power is then sourced from USB/VIN alone. If there is a power deficit (which generally occurs during cellular radio transmission), the additional power is then sourced from the battery as required. The unit can also seamlessly switch back to the battery when other sources of power are suddenly removed.

The DP data pin of the USB is used by the PMIC to detect the presence of a USB power source. It then adjusts the charge current and the limit based on the type of USB power source it detects. This does not always happen successfully since there are a lot of USB hubs and chargers out there that do not meet the USB design guidelines. If the detection is unsuccessful, the PMIC defaults to a 500mA current limit. A user can always adjust these parameters via software.

The microcontroller communicates with the PMIC via an I2C interface (pins PC9 and PA8). This interface allows the microcontroller to read the status of the PMIC and set its various parameters.

Microcontroller

The Electron uses ST Microelectronics's STM32F205RGT6 ARM Cortex M3 microcontroller running at 120MHz.

U-blox cellular module

The u-blox cellular module talks to the microcontroller over a full-duplex USART interface using a standard set of AT commands. The SIM (Nano 4FF) card is directly connected to the u-blox. The power to the SIM card is also provided by the cellular module.

Buffers

Since u-blox module's communication interface operates at 1.8VDC, while the STM32F205RGT6 microcontroller operates at 3.3VDC, we need voltage translators in-between them. This is achieved with two SN74AVC4T245 non-inverting buffers. The default state of the USART pins is set with the help of pull-up and pull-down resistors, and the unused input pins are tied to GND.

3.3V Regulator and fuel gauge

The output (3.8V net) of the PMIC is fed directly to the u-blox cellular module and a 3.3VDC high efficiency switching regulator (TPS62290). This 3.3VDC regulator helps power the microcontroller, fuel gauge and the buffers.

The Electron employs a MAX17043 fuel gauge to monitor the LiPo battery voltage and it's state of charge. The microcontroller communicates with it over an I2C interface (same channel as the PMIC).

Layout

The Electron uses a four layer circuit board. Top layer consists of a signal layer followed by ground (GND), 3.3V power (3V3), and bottom signal.

Bill of materials

Country compatibility

Ordering information

Electrons are available from store.particle.io in single quantities in 2G, and 3G versions.

Product handling

ESD precautions

The Electron contains highly sensitive electronic circuitry and is an Electrostatic Sensitive Device (ESD). Handling a Electron without proper ESD protection may destroy or damage it permanently. Proper ESD handling and packaging procedures must be applied throughout the processing, handling and operation of any application that incorporates Electrons. ESD precautions should be implemented on the application board where the Electron is mounted. Failure to observe these precautions can result in severe damage to the Electron!

Connectors

There are three connectors on the Electron that will get damaged with improper usage. The JST connector on the circuit board, where you plug in the LiPo battery, is very durable but the connector on the battery itself is not. When unplugging the battery, take extra precaution to NOT pull the connector using the wires, but instead hold the plug at its base to avoid putting stress on the wires. This can be tricky with bare hands - nose pliers are your friend here.

The micro B USB connector on the electron is soldered on the PCB with large surface pads as well as couple of through hole anchor points. Despite this reinforcement, it is very easy to rip out the connector if too much stress is put on in the vertical direction.

The U.FL antenna connector is not designed to be constantly plugged and unplugged. The antenna pin is static sensitive and you can destroy the radio with improper handling. A tiny dab of glue (epoxy, rubber cement, liquid tape or hot glue) on the connector can be used securely hold the plug in place.