openrz67-trigger

ESP32 firmware and hardware for remote-triggering the Mamiya RZ67 analog camera over Bluetooth LE. It runs on an ESP32-C3 connected to the camera's electrical remote port and is controlled from the companion apps, openrz67-android and openrz67-ios.

Features

• Instant shutter release
• Bulb mode for remote long exposures
• Self-timer countdown with app-configurable duration
• Runs off a small LiPo, with light sleep between BLE events (see Power)

Hardware

A custom PCB in a 3D-printed case:

Directory	What
pcb/kicad/	KiCad source, generated fab files in out/, design history in notes/
pcb/archive/	exactly what was sent to the fab, one folder per order
case/	parametric build123d enclosure
BOM.md	every part that is not soldered to the PCB (cell, switch, antenna, cables)

The boards in use are rev 2, verified working. The source is rev 3, not yet fabricated; the case fits both.

On the board:

• ESP32-C3FH4 with an FPC antenna on a U.FL connector
• 2× Toshiba TLP172AM PhotoMOS relays (solid-state, isolated) close the shutter contacts
• TI BQ25185 charger (111 mA) and TPS63031 buck-boost, 250 mAh LiPo on BAT1, reverse-battery P-FET (rev 3)
• KCD11 rocker power switch on S3
• J1, unpopulated header for bench logging: 3V3, GND, GPIO21/TX (plus GPIO6 on rev 2)

The firmware also runs on any ESP32-C3 board with two isolated switch channels: assign two output-capable GPIOs in src/main.cpp. On the PCB each GPIO drives a PhotoMOS LED through 150 Ω; the isolated output closes S1 or S2 to camera ground while the GPIO is HIGH. Keep ESP32 ground and camera ground separate.

Pinout

GPIO	Rev 2 (built)	Rev 3 (source)
3	Shutter output S2 (S2_DRV)	Battery sense (VBAT_SENSE): SW_SYS through a 1 MΩ / 1 MΩ divider
4	Shutter output S1 (S1_DRV)	same
6	J1 pin 4, spare	Shutter output S2 (S2_DRV)
20	Status LED (D4, blue)	same

The firmware covers every revision through build flags in platformio.ini: S1_PIN (rev 1), S2_PIN and VBAT_ADC_PIN (rev 3).

LEDs

Both LEDs sit under the same light pipe in the lid.

LED	Meaning
Red D3, steady	Charging. Driven by the charger IC, so it works with the power switch off. Off = full, no USB, or fault
Blue D4, slow soft pulse	On, waiting for a phone
Blue D4, dim steady	Phone connected
Blue D4, full steady	Trigger pulse (2 s) or bulb exposure
Blue D4, fast blink	Countdown running

Camera connector

U4 is a JST S4B-XH-A four-pin side-entry header, opening out of the right board edge:

U4 pin	Camera signal
1	Camera 6 V, unused by the board
2	GND
3	S1
4	S2

Verify the pin 1 orientation before assembling the camera cable.

Camera connection

Viewed from the front, the camera's four-pin remote-control port is:

1. 6 V — wired through, unused by the board
2. GND
3. S1 switch
4. S2 switch

To trigger the shutter, the PhotoMOS outputs short S1/S2 to camera GND. For bulb exposures, set the shutter-speed dial to B. The camera closes the shutter by itself after about 60 seconds even if the switches stay closed.

BLE protocol

The device advertises as OpenRZ67 with service UUID c9239c9e-6fc9-4168-b3aa-53105eb990b0 and characteristic 458d4dc9-349f-401d-b092-a2b1c55f5319. Send commands using Write Without Response. The characteristic is open (no pairing): anyone in radio range can fire the camera, which is accepted for a shutter release.

Also exposed: the standard Device Information Service (0x180A, firmware revision 0x2A26 = FW_VERSION from platformio.ini), and on rev 3:

• characteristic cda71ce6-4af9-4aa2-8d34-329c2acdae09 (read + notify): the SW_SYS voltage in millivolts, little-endian uint16, refreshed every 10 s. On battery this is the cell voltage (about 4200 full, 3500 low); on USB it is the charger's SYS voltage, which is higher. It is not a reliable USB-present flag: treat roughly 4250–4350 as undecided.
• Battery Service (0x180F, Battery Level 0x2A19): the same reading as a percentage, linear from 3500 mV (0 %) to 4200 mV (100 %), which is what phones show without any app.

Single-byte commands (value = button × 10 + state):

Value	Action
11	Trigger shutter with a 100 ms pulse
10	Clear status LED; no shutter action
21	Start bulb mode: holds S1/S2 closed until 20 is sent. Camera dial must be on B
20	End bulb mode
31	Start countdown with the default duration of 10 s
30	Cancel countdown

Three-byte commands [command, duration, action]:

Bytes	Action
[3, n, 1]	Start countdown of n seconds (1–255)
[3, _, 0]	Cancel countdown

Starting a trigger or bulb exposure cancels any pending countdown. Commands are queued in the BLE callback and executed in loop(), so the BLE stack never blocks on shutter timing.

Building

PlatformIO with the pioarduino platform (Arduino core 3.3, ESP-IDF 5.5, NimBLE):

pio run
pio run -t upload

If uploading does not start, hold BOOT, press and release EN, then release BOOT and retry.

Env	Board
default	rev 2
rev1	rev 1 (S1 on GPIO 21)
rev3, rev3-debug	rev 3 (S2 on GPIO 6, battery sense on GPIO 3)
debug	rev 2 with USB CDC logging and VERBOSE=1

The production build has no serial output. UART0 is not used for logging because its RX pin (GPIO 20) drives the status LED; GPIO 21 (UART0 TX) is on J1 for a TX-only dongle.

pio check runs cppcheck over src/; CI (.github/workflows/firmware.yml) builds every env and runs it on each push.

Power

The chip runs at 80 MHz with DFS down to 10 MHz, 0 dBm BLE TX power, and automatic light sleep between BLE events: the radio wakes it for each one, so the phone connection stays up and a trigger arrives as before. custom_sdkconfig in platformio.ini has pioarduino rebuild the Arduino core with CONFIG_PM_ENABLE, tickless idle, BLE modem sleep and the 32.768 kHz crystal X2 as the BLE low-power clock (the first build per machine takes a few minutes). Consequences:

• The status LED runs on LEDC from RC_FAST in keep-alive mode, since the APB clock stops in light sleep.
• Light sleep releases every GPIO, so a PM lock keeps the chip awake while the shutter is open (bulb and the trigger pulse).
• The USB Serial/JTAG port drops off the bus in light sleep, so the debug env stays awake, and flashing a sleeping production build may need the BOOT/EN sequence above.

If X2 does not start, ESP-IDF falls back to the internal RC and BLE keeps working without light sleep. Current draw is not measured yet.

License

MIT, covering the firmware in src/, the KiCad design files in pcb/kicad/ and the enclosure sources in case/. MIT is written for software, but its grant is broad enough to serve a hardware design; the closest hardware-specific equivalent is CERN-OHL-P.

Two things in this repository are not covered, because they are not mine to license:

• The footprints in pcb/kicad/openrz67.pretty/ and the symbols in openrz67.kicad_sym were imported from the EasyEDA/LCSC part libraries.
• The 3D models in pcb/kicad/openrz67.3dshapes/ were fetched per LCSC part number with easyeda2kicad.

Both are redistributed here for convenience under their originators' terms.

Credits

The camera connector pinout that made this project possible was described to me by Julio Ryuuzaki, who built and sold the Bluetooth RZ Blue trigger for years. He answered a cold email in December 2022 with the essentials — four pins, one ground, two live, one unconnected — and the warning that the camera closes the shutter by itself after about a minute in bulb mode. Thank you.