Photon Datasheet
(v015)
Model number:
PHOTONH, PHOTONNOH
void setup() {
Particle.publish("my‐event","The internet just got smarter!");
}
Functional description
Overview
Particle's Internet of Things hardware development kit, the Photon, provides everything you need to
build a connected product. Particle combines a powerful ARM Cortex M3 micro-controller with a
Broadcom Wi-Fi chip in a tiny thumbnail-sized module called the PØ (P-zero).
To get you started quickly, Particle adds a rock solid 3.3VDC SMPS power supply, RF and user
interface components to the PØ on a small single-sided PCB called the Photon. The design is open
source, so when you're ready to integrate the Photon into your product, you can.
The Photon comes in two physical forms: with headers and without. Prototyping is easy with headers
as the Photon plugs directly into standard breadboards and perfboards, and may also be mounted
with 0.1" pitch female headers on a PCB. To minimize space required, the Photon form factor
without headers has castellated edges. These make it possible to surface mount the Photon directly
onto your PCB.
Features
Particle PØ Wi-Fi module
o
Broadcom BCM43362 Wi-Fi chip
o
802.11b/g/n Wi-Fi
o
STM32F205RGY6 120Mhz ARM Cortex M3
o
1MB flash, 128KB RAM
On-board RGB status LED (ext. drive provided)
18 Mixed-signal GPIO and advanced peripherals
Open source design
Real-time operating system (FreeRTOS)
Soft AP setup
FCC, CE and IC certified
Interfaces
Block Diagram
Power
Power to the Photon is supplied via the on-board USB Micro B connector or directly via the VIN pin.
If power is supplied directly to the VIN pin, the voltage should be regulated between 3.6VDC and
5.5VDC. When the Photon is powered via the USB port, VIN will output a voltage of approximately
4.8VDC due to a reverse polarity protection series schottky diode between V+ of USB and VIN.
When used as an output, the max load on VIN is 1A. 3V3 can also be used as an output, but has a
limited overhead of only 100mA available.
(Please refer to
Absolute Maximum Ratings
for more info).
Typical average current consumption is 80mA with 5V @ VIN with Wi-Fi on. Deep sleep quiescent
current is typically 80uA (Please refer to
Recommended Operating Conditions
for more info). When
powering the Photon from the USB connector, make sure to use a quality cable to minimize IR drops
(current x resistance = voltage) in the wiring. If a high resistance cable (i.e., low current) is used,
peak currents drawn from the Photon when transmitting and receiving will result in voltage sag at the
input which may cause a system brown out or intermittent operation. Likewise, the power source
should be sufficient enough to source 1A of current to provide an adequate amount of current
overhead (especially if powering additional circuitry off of VIN).
Warning:
When powering the Photon from long wires on USB and VIN, care should be taken to
protect against damaging voltage transients.
From the Richtek datasheet:
When a ceramic capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load
step at the output can induce ringing at the input, VIN. At best, this ringing can couple to the output and be mistaken
as loop instability. At worst, a sudden inrush of current through the long wires can potentially cause a voltage spike at
VIN large enough to damage the part.
To avoid these voltage spikes, keep input wiring as short as possible. If long wires are unavoidable,
it is advisable to add a 5.1V zener diode or similar transient suppression device from VIN to GND.
Another technique is adding more capacitance to the input using an electrolytic capacitor. Please
refer to
AN-88 by Linear
for a good discussion on this topic.
RF
The RF section of the Photon is a finely tuned impedance controlled network of components that
optimize the efficiency and sensitivity of the Wi-Fi communications.
An RF feed line runs from the PØ module into a SPDT RF-switch. Logic level control lines on the PØ
module select which of the two ports of the RF-switch is connected to the RF feed line. A 100pF
decoupling capacitor is located on each control line. One port is connected to a PCB ceramic chip
antenna, and the other is connected to a u.FL connector for external antenna adaptation. The default
port will be set to the chip antenna.
Additionally, a user API is available to switch between internal, external and even an automatic
mode which continuously switches between each antenna and selects the best signal. All three RF
ports on the RF-switch have a 10pF RF quality DC-blocking capacitor in series with them. These
effectively pass 2.4GHz frequencies freely while blocking unwanted DC voltages from damaging the
RF-switch. All RF traces are considered as tiny transmission lines that have a controlled 50 ohm
impedance.
The chip antenna is impedance matched to the 50 ohm RF feed line via a Pi network comprised of
three RF inductors (1 series, 2 shunt). These values are quite specific to the Photon due to the PCB
construction and layout of the RF section. Even if the Photon's layout design is copied exactly, to
achieve the best performance it would be worth re-examining the Pi network values on actual
samples of the PCB in question.
FCC Approved Antennas
Antenna Type
Dipole antenna
Chip antenna
Manufacturer
LumenRadio
Advanced Ceramic X
MFG. Part #
104-1001
AT7020-E3R0HBA
Gain
2.15dBi
1.3dBi
Peripherals and GPIO
The Photon has ton of capability in a small footprint, with analog, digital and communication
interfaces.
Peripheral Type
Digital
Analog (ADC)
Analog (DAC)
SPI
I2S
Qty
18
8
2
2
1
Input(I) / Output(O)
I/O
I
O
I/O
I/O
FT
[1]
/ 3V3
[2]
FT/3V3
3V3
3V3
3V3
3V3
Peripheral Type
I2C
CAN
USB
PWM
Qty
1
1
1
9
[3]
Input(I) / Output(O)
I/O
I/O
I/O
O
FT
[1]
/ 3V3
[2]
FT
3V3
[4]
3V3
3V3
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.
PWM is available on D0, D1, D2, D3, A4, A5, WKP, RX, TX with a caveat: PWM timer peripheral is
[3]
duplicated on two pins (A5/D2) and (A4/D3) for 7 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 Photon
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.
Photon Pin
D7
D6
D5
D4
D3
JTAG
JTAG_TMS
JTAG_TCK
JTAG_TDI
JTAG_TDO
JTAG_TRST
SWD
SWD/SWDIO
CLK/SWCLK
STM32F205RGY6 Pin
PA13
PA14
PA15
PB3
PB4
PØ Pin #
44
40
43
41
42
PØ Pin Name
MICRO_JTAG_TMS
MICRO_JTAG_TCK
MICRO_JTAG_TDI
MICRO_JTAG_TDO
MICRO_JTAG_TRSTN
Default Internal
[1]
~40k pull-up
~40k pull-down
~40k pull-up
Floating
~40k pull-up
