OpenMV Cam H7 Plus¶

The OpenMV Cam H7 Plus pairs the STMicroelectronics STM32H743 (Cortex‑M7 @ 480 MHz) with 32 MB of external SDRAM, 32 MB of QSPI flash, a hardware JPEG codec, and the OV5640 5 MP camera module on a removable carrier. The extra memory is well suited to high‑resolution capture and large image buffers.

For full datasheet, photos, and dimensions see the OpenMV Cam H7 Plus product page.

Highlights¶

STMicroelectronics STM32H743 Cortex‑M7 at 480 MHz (1027 DMIPS).
Hardware JPEG encoder/decoder.
32 MB external SDRAM (32‑bit @ 100 MHz, 400 MB/s) plus 1 MB internal SRAM.
2 MB internal flash + 32 MB external QSPI flash (~100 MB/s read).
OV5640 5 MP rolling‑shutter sensor.
Full‑speed USB (12 Mb/s) — appears as VCP + USB mass storage to the host.
microSD socket — SD up to 2 GB, SDHC up to 32 GB, SDXC up to 2 TB.
LiPo battery connector (no on‑board charger — supply a charged cell or run from VIN/USB).
10 I/O pins, 5 V tolerant with 3.3 V output, 25 mA per pin (120 mA total across the header), interrupt‑capable. P6 is not 5 V tolerant when used in ADC or DAC mode.
User RGB LED and two high‑power 850 nm IR LEDs for active lighting in low‑light vision.

Note

The H7 Plus has no on‑board power management chip: there’s no battery charger, no battery‑voltage ADC, no charging / power‑status LEDs, and no hardware power button. Connect a pre‑charged LiPo to the battery JST or run the board from USB / VIN.

Pinout¶

Pin reference¶

Pin name	Function
P0	UART1 RX / SPI2 MOSI
P1	UART1 TX / SPI2 MISO
P2	SPI2 SCK / FDCAN2 TX
P3	SPI2 NSS (CS) / FDCAN2 RX
P4	I2C2 SCL / UART3 TX / TIM2 CH3
P5	I2C2 SDA / UART3 RX / TIM2 CH4
P6	ADC / DAC / TIM2 CH1
P7	I2C4 SCL / TIM4 CH1
P8	I2C4 SDA / TIM4 CH2
P9	digital I/O
RESET	pull to GND to reset the board
SYN	frame‑sync pad — wired to the camera sensor only
BOOT0	pull to 3.3 V at power‑on for DFU / ROM bootloader
LED_RED	RGB LED red channel (active low)
LED_GREEN	RGB LED green channel (active low)
LED_BLUE	RGB LED blue channel (active low)
LED_IR	high‑power IR LEDs (both channels driven together)

Note

The SYN pad on the header is connected directly to the camera sensor’s trigger / exposure line — it does not route to the MCU on the H7 Plus. Drive or read it externally; you can’t toggle it from MicroPython.

Power pins¶

3.3V — regulated 3.3 V rail. Up to 250 mA available for shields (less if the microSD card is in use). Unlike the newer cameras this pin is bidirectional — see the warning below.
VIN — 3.6 – 5 V input. Powers the board through the on‑board regulator.
GND — common ground.

A 3.7 V LiPo connector is also present, but the H7 Plus does not have a battery charger — connect a pre‑charged cell, or supply VIN / USB instead.

Note

When both USB and VIN/LiPo are present, the VIN/LiPo input wins — the on‑board power switch picks it over USB to power the board.

Warning

The battery connector and VIN are tied together on the H7 Plus. Do not plug in a LiPo and apply VIN at the same time — the two supplies will fight each other and can damage the battery, the board, or both.

Warning

You may power the H7 Plus by feeding 3.3 V directly into the 3.3V pin if you don’t want to go through the on‑board regulator. In that case, do not also apply VIN or USB power at the same time — back‑driving the regulator while another supply is active can permanently damage and destroy the camera.

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 the STM32 ROM bootloader (DFU mode). OpenMV IDE uses this mode to reflash the on‑board bootloader.

The board exposes an SWD debug header (RST / SWCLK / SWDIO / SWO) next to the GPIO header, compatible with ST‑LINK and SEGGER J‑Link adapters.

Note

The SWO trace pin is shared with the camera header’s SPI clock line. SWO can’t be used at the same time as any camera module that communicates with the MCU over SPI — for example the FLIR® Lepton® Adapter Module — pick one or the other.

Onboard peripherals¶

LEDs¶

The H7 Plus has a single user RGB LED plus a pair of high‑power 850 nm IR 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()

IR LEDs — both LEDs are driven together through the LED_IR pin. LED_IR is wired active high in hardware while the firmware treats every other on‑board LED as active low, so use low() / high() rather than on() / off() (which would invert the sense):
```
from machine import LED

ir = LED("LED_IR")
ir.low()    # turn IR illumination ON
ir.high()   # turn IR illumination OFF
```

Camera sensor¶

The OV5640 is driven through the csi — camera sensors module:

import csi

cam = csi.CSI()
cam.reset()
cam.pixformat(csi.RGB565)
cam.framesize(csi.QVGA)
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.

Machine learning¶

ml — Machine Learning runs quantised TFLite models on the Cortex‑M7 with CMSIS‑NN kernels — fast enough for compact detectors at a few frames per second. Models on the read‑only /rom filesystem load directly from flash without copying to RAM. Here’s a 128×128 BlazeFace detector overlaying the detected face and its six landmarks on every frame:

import csi
import time
import ml
from ml.postprocessing.mediapipe import BlazeFace

# Initialize the sensor.
csi0 = csi.CSI()
csi0.reset()
csi0.pixformat(csi.RGB565)
csi0.framesize(csi.VGA)
csi0.window((400, 400))

# Load built-in face detection model
model = ml.Model("/rom/blazeface_front_128.tflite", postprocess=BlazeFace(threshold=0.4))
print(model)

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

    # faces is a list of ((x, y, w, h), score, keypoints) tuples
    for r, score, keypoints in model.predict([img]):
        ml.utils.draw_predictions(img, [r], ("face",), ((0, 0, 255),), format=None)

        # keypoints is a ndarray of shape (6, 2)
        # 0 - right eye (x, y)
        # 1 - left eye (x, y)
        # 2 - nose (x, y)
        # 3 - mouth (x, y)
        # 4 - right ear (x, y)
        # 5 - left ear (x, y)
        ml.utils.draw_keypoints(img, keypoints, color=(255, 0, 0))

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

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, 5 V tolerant on the input side, and can sink/source up to 25 mA per pin (120 mA total across the whole header).

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
UART1	P1	P0
UART3	P4	P5

from machine import UART

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

I²C¶

Bus	SCL	SDA
I2C2	P4	P5
I2C4	P7	P8

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

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 (FDCAN)¶

Bus	TX	RX
FDCAN2	P2	P3

from machine import CAN

can = CAN(2, 500_000)
can.send([0xDE, 0xAD, 0xBE, 0xEF], 0x123)
print(can.recv())

ADC and DAC¶

P6 is the only user analog pin. It can be used as either a 12‑bit ADC input or a DAC output.

ADC — full‑scale at 3.3 V at the pin:

from machine import ADC
import time

adc = ADC("P6")
while True:
    voltage = adc.read_u16() * 3.3 / 65535
    print(voltage)
    time.sleep_ms(100)

DAC — through pyb.DAC. The 8‑bit value covers 0–3.3 V:

from pyb import DAC

dac = DAC("P6")
voltage = 1.65
dac.write(int(voltage / 3.3 * 255))

In ADC or DAC mode P6 is 3.3 V tolerant only — do not feed it 5 V.

PWM¶

Pin	Timer / channel
P4	TIM2 CH3
P5	TIM2 CH4
P6	TIM2 CH1
P7	TIM4 CH1
P8	TIM4 CH2

Note

TIM1 is reserved by the firmware to generate the camera sensor’s pixel clock, so the TIM1 channels that are physically on P0/P1/P2 cannot be used for user PWM without breaking the camera.

TIM4 is shared with pyb.Servo — instantiating a servo reconfigures the whole timer for 50 Hz operation, so don’t mix machine.PWM on P7/P8 with pyb.Servo in the same script.

Drive any of them via machine.PWM:

from machine import Pin, PWM

pwm = PWM(Pin("P7"), 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:

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())

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 H7 Plus 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 H7 Plus build.