OpenMV N6¶

The OpenMV N6 is built around the STMicroelectronics STM32N657 (Cortex‑M55 @ 800 MHz) with a 1 GHz on‑chip NPU rated at 600 GOPS INT8. The board pairs the NPU with the PAG7936 1 MP global‑shutter sensor on a removable carrier, gigabit Ethernet, USB‑C high‑speed, Wi‑Fi, and Bluetooth 5.1, and runs YOLOv8/YOLOv11 inference at 30 FPS alongside live video streaming.

For full datasheet, photos, and dimensions see the OpenMV N6 product page.

Highlights¶

STM32N657 Cortex‑M55 at 800 MHz (1280 DMIPS) with ARM Helium 128‑bit SIMD — 6.4 gigaops vector throughput.
1 GHz NPU, 600 GOPS INT8 — runs YOLOv8/YOLOv11 detection at 30 FPS.
ISP for up to 5 MP RAW Bayer, 2D GPU for scaling and 3D rotation, H.264 encode to 1080p, and hardware JPEG codec.
64 MB external SDRAM (16‑bit @ 200 MHz DDR, 800 MB/s) plus 4.2 MB internal SRAM and 32 MB octal flash (200 MHz DDR, 400 MB/s).
PAG7936 1 MP color global‑shutter sensor.
Onboard IMU (accelerometer + gyroscope) and microphone for audio + motion fusion.
High‑speed USB‑C (480 Mb/s, 1.5 A current limit), gigabit Ethernet (PoE‑capable via shield), Wi‑Fi a/b/g/n + Bluetooth 5.1 (chip antenna or U.FL option).
microSD socket — SD up to 2 GB, SDHC up to 32 GB, SDXC up to 2 TB.
LiPo charger (500 mA fast charge), battery‑voltage ADC, RTC with 8 KB backup RAM and a dedicated backup‑battery pin.
18 I/O pins, all 3.3 V output / 3.3 V tolerant, 20 mA per pin, interrupt‑capable.
User RGB LED, user button, and a separate status LED for charging / USB / VIN power.

Warning

The N6’s I/O pins are not 5 V tolerant. Do not connect the device directly to a 5 V MCU like the Arduino Mega. Power the N6 through VIN only.

Pinout¶

Pin reference¶

Pin name	Function
P0	SPI2 MOSI / I2S2 SDO
P1	SPI2 MISO / I2S2 SDI
P2	SPI2 SCLK / UART4 TX / CAN1 TX / I2S2 CK
P3	SPI2 SS / UART4 RX / CAN1 RX / I2S2 WS
P4	I2C2 SCL / UART3 TX / TIM2 CH3 / I3C2 SCL
P5	I2C2 SDA / UART3 RX / TIM2 CH4 / I3C2 SDA
P6	TIM12 CH1 (no ADC on this pin — see `P6_ADC`)
P6_ADC	dedicated 12‑bit ADC input (tied internally to P6)
P7	TIM4 CH1
P8	TIM4 CH2
P9	TIM17 CH1
P10	TIM15 CH2 / frame sync I/O
P11	wakeup (active low, WKUP3)
P12	RESET — pull to GND to reset the board (not a GPIO)
P13	UART7 RX
P14	UART7 TX
P15	SPI4 CS
P16	SPI4 SCK
P17	SPI4 MISO
P18	SPI4 MOSI
SW	user button (active low)
ONOFF (SW2)	deep‑sleep wakeup button (active low, WKUP2)
ST	low on VIN power, high on USB power
CHG	active‑low; low while an attached LiPo battery is charging
PG	active‑low; low when VIN or USB power is present
BAT_ADC	internal ADC channel measuring the attached LiPo battery voltage
LED_RED	RGB LED red channel (active low)
LED_GREEN	RGB LED green channel (active low)
LED_BLUE	RGB LED blue channel (active low)

Note

The P10 frame‑sync line is a shared bus. It is wired to the MCU, the camera sensor’s trigger / exposure pin, and the user header all at once. Direction is application‑defined — the MCU, the sensor, or an external signal can drive it depending on how the sensor is configured (some sensors can use the same pin as a trigger input or an exposure output). Make sure only one driver is active at a time.

Note

ONOFF and P11 are referenced to the always‑on RAW rail (not the switched 3.3 V rail), so they remain functional while the rest of the board is in deep sleep / low‑power mode. Both inputs are active low.

These pins go through level shifters so they can ride on the RAW rail. If you absolutely need 3.3 V‑direct GPIO behaviour on ONOFF or P11 (for example to drive them from a 3.3 V MCU without going through the shifter), the board exposes pull‑up and 0‑ohm jumper pads that let you bypass the shifter. This is an advanced hardware rework — most users should leave it alone.

Note

P15–P18 are shared with the Gigabit Ethernet PHY, which is wired up and active by default. To use these pins as user I/O you must reflow the 0‑ohm resistor on the back of the board over to the GPIO position. This only disables gigabit Ethernet — 10/100 Mb/s Ethernet keeps working on its dedicated pins.

Power pins¶

3.3V — regulated 3.3 V rail. Output only on the N6 — do not feed external power into this pin. Up to 1 A available for shields.
VIN — 5 V input. Powers the board and the on‑board LiPo charger.
RAW — input/output, always‑on (3.6 V – 5 V). Carries whichever source is active (VIN, USB, or attached battery), and can also be used as an input. You must drive RAW through a series diode when sourcing power into it — otherwise current will flow back into VIN/USB and damage the supply or the on‑board protection.
GND — common ground.

Note

The on‑board power management chip automatically picks whichever of USB or VIN has the higher voltage to power the board and the battery charger. If a LiPo is attached it charges on the leftover headroom, and the controller falls back to the battery to keep the board running if VIN/USB sag or are unplugged.

Note

The back of the board has solder pads for an external 3.3 V RTC backup battery. Wiring a coin cell to these pads keeps the RTC and 8 KB of backup RAM running while the rest of the board is unpowered.

Ethernet pins¶

The N6 exposes the Ethernet PHY’s MDI pairs on dedicated pads next to the GPIO header. The MDI pins are not safe to wire straight to an RJ45 — Ethernet magnetics (an isolation transformer, either built into a magjack or on the shield) are required between the PHY and the cable. The OpenMV PoE shield includes them; if you’re rolling your own jack, use a magnetics‑integrated RJ45 or an external transformer.

ETH_LED — link/activity LED. Active low when a link is up; flashes on traffic.
DA P / DA N — pair A (TX in 10/100, used by all speeds).
DB P / DB N — pair B (RX in 10/100, used by all speeds).
DC P / DC N — pair C, only used at gigabit.
DD P / DD N — pair D, only used at gigabit.

10/100 Mb/s only needs pairs A and B. Gigabit needs all four pairs A–D.

Recovery and debug pins¶

RESET — pull to GND to reset the board. Releasing it lets the MCU start up normally.
BOOT0 — pull to 3.3 V while powering the board to enter ROM bootloader mode. OpenMV IDE uses this mode to reflash the on‑board bootloader.
BOOT1 — switch that puts the board into developer mode for use with ST’s tooling (an ST‑LINK attached to the ARM 10‑pin SWD/JTAG header). Leave this disabled for normal operation with OpenMV firmware and tools.

A dedicated ARM 10‑pin SWD/JTAG header is fitted, compatible with ST‑LINK and SEGGER J‑Link adapters.

Onboard peripherals¶

LEDs¶

The N6 has two RGB LEDs:

User RGB LED — software‑controllable, exposed as LED_RED, LED_GREEN and LED_BLUE:

from machine import LED

LED("LED_RED").on()
LED("LED_GREEN").on()
LED("LED_BLUE").on()

Power LED — driven directly by the on‑board power management hardware, no software control. Use it to read what the supply is doing at a glance.

While running:

Channel

Meaning

Blue

VIN is powering the board (off on USB)

Green

USB or VIN power present

Red

charging an attached LiPo battery

In deep sleep all channels are off except Red, which still lights while a LiPo is charging.

Channel	Meaning
Blue	VIN is powering the board (off on USB)
Green	USB or VIN power present
Red	charging an attached LiPo battery

User buttons¶

The N6 has two buttons:

SW — general‑purpose user button. Active when pulled low.
ONOFF (SW2) — wakeup button. The only button that can bring the board out of deep sleep.

from machine import Pin

sw    = Pin("SW",    Pin.IN)   # user button
onoff = Pin("ONOFF", Pin.IN)   # SW2 — wakes from deep sleep
print(sw.value(), onoff.value())

To put the board into deep sleep and have ONOFF (SW2) wake it back up, just call machine.deepsleep() — no wakeup configuration is required, the button is wired straight to the WKUP2 input:

import machine

machine.deepsleep()   # press ONOFF (SW2) to wake the board

You can also wire ONOFF up as a soft power switch. Trigger on the rising edge — the line settles high after the user releases the button, so the next press is unambiguously a wake event:

import machine
from machine import Pin

def power_off(_):
    machine.deepsleep()

Pin("ONOFF", Pin.IN).irq(power_off, Pin.IRQ_RISING)

# ...rest of the application runs here. Press ONOFF once to sleep,
# press it again to wake.

Power status pins¶

Three active‑low status inputs let firmware see what the on‑board power management chip is doing:

ST — low when the board is running on VIN, high when running on USB power.
CHG — low while an attached LiPo battery is charging.
PG — low when VIN or USB power is present.

from machine import Pin

on_vin    = not Pin("ST",  Pin.IN).value()
charging  = not Pin("CHG", Pin.IN).value()
power_ok  = not Pin("PG",  Pin.IN).value()

Camera sensor¶

The PAG7936 is driven through the csi — camera sensors module:

import csi

cam = csi.CSI()
cam.reset()
cam.pixformat(csi.RGB565)
cam.framesize(csi.HD)         # 1280×720
cam.snapshot(time=2000)       # let auto‑exposure settle

while True:
    img = cam.snapshot()

The sensor sits on a removable module — swap it for any of the other OpenMV camera modules (global shutter, thermal, higher resolution, etc.) without changing the rest of the board.

NPU¶

The N6’s 1 GHz Neural‑ART NPU (600 GOPS INT8) is exposed through the ml — Machine Learning module. Models stored on the read‑only /rom filesystem load directly from flash without copying to RAM, so even large detectors fit comfortably alongside the live framebuffer. Run a YOLOv8 detector on every frame and draw the predictions on top of the live image:

import csi
import time
import ml
from ml.postprocessing.ultralytics import YoloV8

# Initialize the sensor.
csi0 = csi.CSI()
csi0.reset()
csi0.pixformat(csi.RGB565)
csi0.framesize(csi.VGA)

# Load YOLO V8 model from ROM FS.
model = ml.Model("/rom/yolov8n_192.tflite", postprocess=YoloV8(threshold=0.4))
print(model)

# Visualization parameters.
n = len(model.labels)
model_class_colors = [(int(255 * i // n), int(255 * (n - i - 1) // n), 255) for i in range(n)]

clock = time.clock()
while True:
    clock.tick()
    img = csi0.snapshot()

    # boxes is a list of list per class of ((x, y, w, h), score) tuples
    boxes = model.predict([img])

    # Draw bounding boxes around the detected objects
    for i, class_detections in enumerate(boxes):
        rects = [r for r, score in class_detections]
        labels = [model.labels[i] for j in range(len(rects))]
        colors = [model_class_colors[i] for j in range(len(rects))]
        ml.utils.draw_predictions(img, rects, labels, colors, format=None)

    print(clock.fps(), "fps")

Microphone¶

The on‑board mic is captured through audio — Audio Module. Each buffer arrives as a signed‑16‑bit PCM bytearray, which makes it trivial to feed into ulab/numpy for quick DSP. A simple loudness detector — print whenever the RMS volume crosses a threshold:

import audio
from ulab import numpy as np

def loudness(pcmbuf):
    samples = np.array(np.frombuffer(pcmbuf, dtype=np.int16), dtype=np.float)
    rms = np.sqrt(np.mean(samples ** 2))
    if rms > 10000:
        print("Loud!", int(rms))

audio.init(channels=1, frequency=16000, gain_db=24)
audio.start_streaming(loudness)

IMU¶

The on‑board accelerometer + gyroscope under the camera module is exposed through imu — imu sensor:

import imu
import time

while True:
    print(imu.acceleration_mg())   # (x, y, z) in milli‑g
    print(imu.angular_rate_mdps()) # (x, y, z) in milli‑deg/s
    time.sleep_ms(100)

Wi‑Fi¶

The on‑board CYW43439 is exposed via network — network configuration as a station interface. After connecting, ipconfig("addr4") returns the (ip, netmask) pair:

import network, time

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect("ssid", "password")
while not wlan.isconnected():
    time.sleep(1)
print("Wi‑Fi IP:", wlan.ipconfig("addr4")[0])

Bluetooth¶

The same CYW43439 also exposes Bluetooth 5.1. Use aioble — Async BLE for asyncio‑friendly BLE — for example, advertise as a peripheral and wait for a central to connect:

import asyncio
import aioble

async def run():
    while True:
        conn = await aioble.advertise(250_000, name="OpenMV-N6")
        print("Connected:", conn.device)
        await conn.disconnected()

asyncio.run(run())

Ethernet¶

When an RJ45 (with magnetics) is connected to the MDI pads, the gigabit PHY appears as a LAN interface. DHCP runs automatically once the link comes up:

import network, time

lan = network.LAN()
lan.active(True)
while not lan.isconnected():
    time.sleep(1)
print("Ethernet IP:", lan.ipconfig("addr4")[0])

microSD card¶

When a card is inserted it is mounted automatically at /sdcard and is usable through the regular file system:

import os

for entry in os.listdir("/sdcard"):
    print(entry)

Bus reference¶

GPIO¶

Use machine.Pin to read or drive any of the silkscreened pins. Outputs are 3.3 V CMOS and can sink/source up to 20 mA per pin.

from machine import Pin

out = Pin("P0", Pin.OUT)
out.on()
out.off()
out.value(1)

inp = Pin("P1", Pin.IN, Pin.PULL_UP)
print(inp.value())

Any input pin can also fire an interrupt on edge transitions:

def handler(pin):
    print("triggered:", pin)

Pin("P1", Pin.IN, Pin.PULL_UP).irq(
    handler, Pin.IRQ_FALLING | Pin.IRQ_RISING,
)

UART¶

Bus	TX	RX
UART3	P4	P5
UART4	P2	P3
UART7	P14	P13

from machine import UART

uart = UART(3, baudrate=115200)
uart.write("hello")
uart.read(5)

I²C¶

Bus	SCL	SDA
I2C2	P4	P5

from machine import I2C

i2c = I2C(2, freq=400_000)
i2c.scan()
i2c.writeto(0x76, b"hi")

The same hardware can also be used in target (slave) mode through machine.I2CTarget to expose a memory region to another I²C controller:

from machine import I2CTarget

buf = bytearray(32)
target = I2CTarget(2, addr=0x42, mem=buf)

SPI¶

Bus	MOSI	MISO	SCK	CS
SPI2	P0	P1	P2	P3
SPI4	P18	P17	P16	P15

from machine import SPI
from machine import Pin

spi = SPI(2, baudrate=10_000_000)
cs = Pin("P3", Pin.OUT, value=1)   # CS is not driven by the SPI peripheral

cs.value(0)
spi.write(b"hello")
cs.value(1)

CAN¶

Bus	TX	RX
CAN1	P2	P3

from machine import CAN

can = CAN(1, 500_000)
can.send([0xDE, 0xAD, 0xBE, 0xEF], 0x123)
print(can.recv())

ADC¶

Both ADC channels go through an op‑amp buffered voltage divider before hitting the MCU, so read_u16() is mapped to a different full‑scale input voltage on each pin.

Pin	Full‑scale	Notes
P6_ADC	~3.3 V	general‑purpose pad, tied internally to P6
BAT_ADC	~5.0 V	internal channel for the LiPo battery

from machine import ADC
import time

adc = ADC("P6_ADC")
bat = ADC("BAT_ADC")

while True:
    print("P6:", adc.read_u16() * 3.3 / 65535, "V")
    print("BAT:", bat.read_u16() * 5.0 / 65535, "V")
    time.sleep_ms(100)

PWM¶

Pin	Timer / channel
P4	TIM2 CH3
P5	TIM2 CH4
P6	TIM12 CH1
P7	TIM4 CH1
P8	TIM4 CH2
P9	TIM17 CH1
P10	TIM15 CH2

Drive any of them via machine.PWM:

from machine import Pin, PWM

pwm = PWM(Pin("P6"), freq=1_000, duty_u16=32768)

Software bit‑banged buses¶

machine.SoftI2C and machine.SoftSPI work on any GPIO if you need an extra bus.

Timing¶

time¶

The time module covers blocking delays, monotonic ticks, and elapsed‑time measurement:

import time

time.sleep(1)              # seconds
time.sleep_ms(500)
time.sleep_us(10)

start = time.ticks_ms()
# ...do work...
elapsed = time.ticks_diff(time.ticks_ms(), start)

Virtual timers¶

machine.Timer schedules periodic or one‑shot callbacks without consuming a hardware timer slot. Pass -1 as the id to use a virtual (software) timer:

from machine import Timer

one_shot = Timer(-1)
one_shot.init(period=5_000, mode=Timer.ONE_SHOT,
              callback=lambda t: print("once"))

periodic = Timer(-1)
periodic.init(period=2_000, mode=Timer.PERIODIC,
              callback=lambda t: print("tick"))

Period values are in milliseconds. Call deinit() to stop and release the slot.

Real‑time clock¶

machine.RTC keeps wall‑clock time across resets and (with the optional 3.3 V backup battery wired to the rear pads, see Power pins) across full power loss:

from machine import RTC

rtc = RTC()
rtc.datetime((2026, 4, 30, 4, 12, 0, 0, 0))   # Y, M, D, weekday, h, m, s, subsec
print(rtc.datetime())

The RTC also runs through deep sleep, so you can use it as a wakeup source for machine.deepsleep().

Watchdog¶

machine.WDT resets the board if the application hangs. Once started it can’t be stopped or reconfigured — feed it periodically inside your main loop:

from machine import WDT

wdt = WDT(timeout=5_000)   # 5 second window
while True:
    # ...do work...
    wdt.feed()

Boot and runtime info¶

USB bootloader window¶

On every power‑up the camera runs a short bootloader (a few seconds) that lets OpenMV IDE update the firmware without the user having to enter DFU mode. After the window expires the bootloader hands off to boot.py and then main.py.

A running script can re‑enter the bootloader on demand by calling machine.bootloader():

import machine

machine.bootloader()

Filesystem and boot order¶

The N6 firmware mounts up to three filesystems on boot:

Internal flash — always mounted at /flash. Holds main.py and README.txt by default; created on the very first boot.
microSD card — if a card is inserted it is mounted at /sdcard.
ROMFS — read‑only, memory‑mapped filesystem at /rom used to ship large data assets (e.g. AI models) that benefit from zero‑copy access. Mounted automatically by MicroPython at startup, before any user Python runs.

After mounting, the working directory is set to /sdcard when the card is present, otherwise /flash. The interpreter then runs scripts from that directory:

boot.py is executed on every soft reset (cold boot, Ctrl‑D from the REPL, or whenever the running script returns).
main.py is executed only on cold boot, immediately after boot.py. Subsequent soft resets re‑run boot.py but drop straight to the REPL — to re‑run main.py you have to fully reset the board.

Dropping a boot.py or main.py onto the SD card overrides the copy in flash without touching it — both files are looked up in the boot directory (/sdcard when the card is mounted, otherwise /flash).

The default main.py shipped on a freshly flashed board just blinks the user RGB LED’s blue channel as a heartbeat (two short pulses, short gap), so you can tell the firmware booted cleanly without any host attached.

sys.path is extended to include all three filesystems and their lib/ subdirectories, so importable modules can live in /flash/lib, /sdcard/lib, or /rom/lib.

To force the system to ignore an inserted SD card (for example to run the flash main.py even with a card present), create an empty file named SKIPSD at the root of /flash.

When connected over USB, the boot filesystem (/sdcard if a card is present, otherwise /flash) also enumerates as a USB mass‑storage drive on the host, letting you edit boot.py, main.py, and any other files directly. Eject the drive before resetting the camera so the host flushes its cached writes.

Note

Because the OS treats the drive as a passive block device, files created or modified by code running on the OpenMV Cam will not show up until the host re‑mounts the drive. If both the OS and the OpenMV Cam write the same filesystem at the same time, the OS will win and overwrite changes made by the camera. Use the SD card for any data the script writes back, and remount before reading those files from the host.

Note

The user RGB LED’s red channel may briefly light up while the host is reading from or writing to the USB mass‑storage drive — this is a firmware‑driven activity indicator, not a fault.

Hard‑fault indicator¶

If the user RGB LED is rapidly cycling through all colours — fast enough that it tends to look like a twinkling white LED rather than distinct hues — the firmware has hit an unrecoverable hard fault. Reflash the firmware to recover; if reflashing doesn’t help, the board may be physically damaged.

Software libraries¶

See the library index for the full list of modules — including which ones are unique to the N6 build.