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Bluetooth interface for STAG 4 or QBOX gas installation

weryfany  37 29406 Cool? (+14)
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TL;DR

  • Built a compact Bluetooth interface for STAG 4 or QBOX gas installations, combining a STAG plug, an HC-05 Bluetooth module, and a universal remote-control housing.
  • A reed switch and a nearby magnet reprogram the interface between STAG 4 and QBOX modes, with power from a 7805 stabilizer or a 4.9V step-down converter.
  • The original interface cost about PLN 80, and any laptop with Bluetooth replaced the old RS-232 cable setup.
  • It corrected settings and updated drivers in multiple vehicles, and the STAG QBOX controller can communicate with an Android phone app for parameter viewing.
AI summary based on the discussion. May contain errors.
Hello everyone, I was inspired by another thread on the electrode related to the 232 interface for the gas installation.
I made the interface presented here over 2 years ago, in the meantime, about a week, new versions were created. The final version was quite universal. It can be reprogrammed to STAG 4 or QBOX by bringing the magnet closer.

I used the STAG plug, the HC-05 bluetooth module, the 7805 stabilizer (or the step-down converter set to 4.9V), the reed switch which has contacts for reprogramming the settings, universal remote control housing, hot glue, heat shrink tubing.
Thanks to this interface, I corrected settings and updated drivers in my and other vehicles.

I wanted it to be small, handy, durable and that's what it is.

Photo of the first version:





And the final one after all modifications:



And the end result:



The original one at the moment is about PLN 80
but over 2 years ago it was not so colorful.

Any laptop with bluetooth was enough to work, and the 232 port and cable tethering were a thing of the past.

Each intervention in the controller is recorded / saved in it (in the controller).
The installer, if he hooks up and programmed on the same computer, will pop up a message that he was programmed with a different computer.
It was not like that in my case.

In the STAG QBOX controller it communicates with the Android phone application (parameter preview)

HC-05 settings:



AT commands:

Code: ARM assembler
Log in, to see the code
About Author
weryfany
weryfany wrote 1020 posts with rating 148 , helped 59 times. Live in city Zamość. Been with us since 2007 year.

Comments

Sebek6543210 30 Jan 2019 06:41

"interference" - that is, the readings are recorded, doesn't it count? Was there a lot of combining with the HC-05 configuration? [Read more]

byrrt 30 Jan 2019 08:42

How is communication with these two drivers different? What is this reed switch for? [Read more]

weryfany 30 Jan 2019 08:49

Just connecting to the driver, if I remember correctly (over 2 years ago it was) A banal configuration, a USB programming cable that saves disks from TX, RX and GND. I will add 3 more photos because... [Read more]

jawa1993 30 Jan 2019 11:57

Each connection to the controller is saved. I don't remember which and which company the new drivers have a connection counter, after which they are "full", they are blocked and need to be replaced... [Read more]

weryfany 30 Jan 2019 13:40

If there are such drivers, a colleague could mention their names, what companies / models they are, because STAG does not protect its devices in this way, and that's why I always choose STAG, because... [Read more]

Sebek6543210 30 Jan 2019 20:59

Were there attempts to connect with other drivers, e.g. Lovato? [Read more]

weryfany 30 Jan 2019 21:03

Not only STAG 4 and after reprogramming STAG QBOX I tried with Zenit, despite supplying external power after the first attempt, I gave up due to lack of time. [Read more]

noel200 01 Feb 2019 08:47

So the hc-05 module fits right out of the box? I do not need to change anything? You only entered the password and name, but it is not essential for the connection between the module and the stag, and... [Read more]

zbyz 01 Feb 2019 18:22

Hello. I will present you my battles with a similar topic. A year ago, I glued something similar to the STAG-300 ISA2, but due to my inattention, I released my HC and probably the communication inputs... [Read more]

weryfany 01 Feb 2019 19:09

I programmed the HC-05 as above 3 print screens - 9600 for stag 4 (I had the eco version) Well, it makes no sense to pour the whole glue. I will tell you that the versions with the 7805 stabilizer, despite... [Read more]

MACIEK_M 08 Feb 2019 19:45

Hello, great idea, I have the elements in a drawer, I will try to replace the wired interface with this one, we will see how it works. I didn't think it was that simple. :D [Read more]

MACIEK_M 11 Feb 2019 18:19

Werfany wrote: And you could enter the parameters for connecting to QBOX, I have GO-FAST, and the interface for STAG 4 ECO does not connect to it. [Read more]

weryfany 11 Feb 2019 19:51

At 100%, the speed of communication is higher, but I do not remember how much than in stag 4 [Read more]

MACIEK_M 11 Feb 2019 19:56

Can the communication speed be "previewed" on the wired internet connection to GO-FAST, because I have one, and I wanted BT? Are they unrelated? [Read more]

weryfany 12 Feb 2019 20:32

I have no idea what it's like with a wired one, I've never had one [Read more]

Arek1984 17 Feb 2019 03:27

Here you can find everything about the interface. https://lpg-forum.pl/interkietas-bluetooth-diy-t23813-795.html [Read more]

MACIEK_M 17 Feb 2019 10:43

-> Arek1984 Very helpful link, everything is thanks. :D [Read more]

MACIEK_M 04 Apr 2019 20:26

Hello, it took a while, but it worked. My HC-05 module failed to reprogram with Arduino, I don't know why. :D I had to order from Ali .. TTL UART converter, by the way I ordered a small 5V pulse... [Read more]

weryfany 05 Apr 2019 18:09

I would stick to the casing because it looks delicate, but it is important that it works and there is POWER; D [Read more]

FAQ

TL;DR: DIY Bluetooth interfaces for STAG 4/QBOX cost ≈ PLN 20 instead of the PLN 80 OEM unit; "I updated the driver without any problems" [Elektroda, weryfany, post #19361578] Build uses an HC-05 at 9600 or 57600 baud and a 5 V regulator.

Why it matters: Saves money, removes dangling cables, and lets you tune LPG maps from a phone.

Quick Facts

• OEM Bluetooth dongle price: ~PLN 80 [Elektroda, weryfany, post #17741134] • DIY parts cost: approx. PLN 15–25 (HC-05, 7805/step-down, plug, case) [Elektroda, weryfany, post #17741134] • STAG 4 baud rate: 9600 8N1 [Elektroda, weryfany, post #17741134] • QBOX / GoFast baud rate: 57600 8N1 [Elektroda, MACIEK_M, post #17886237] • Recommended supply range: 7–16 V car rail → 5 V regulator (≤ 50 mA) [Elektroda, weryfany, post #17747760]

Which gas ECU models work with a re-programmed HC-05?

Confirmed: STAG 4, STAG QBOX, Go Fast and CCY BT Basic QBOX when set to the correct baud rate [Elektroda, weryfany, #17743387; #19360967]. Others like Zenit may need different commands and were not fully tested [Elektroda, weryfany, post #17743387]

What AT commands do I need for a STAG 4 interface?

  1. Enter AT mode (key pin high).
  2. Send AT+UART=9600,0,0
  3. Send AT+PSWD=1234
  4. Send AT+NAME=AC STAG This keeps the default 8N1 framing and preserves ECU compatibility [Elektroda, weryfany, post #17741134]

How do I switch the dongle between STAG 4 and QBOX?

Install a reed switch on the HC-05 KEY pin. Bringing a magnet closes the switch, letting you re-flash the baud setting to 57600 for QBOX, then remove the magnet to return to normal mode [Elektroda, weryfany, post #17741542]

Why does my connection drop after a few seconds?

Voltage sag or noise on the 5 V rail often causes resets. Replace 78L05 with a buck step-down rated ≥ 500 mA and add 100 µF filtering; users report stable links after the swap [Elektroda, MACIEK_M, post #18468145]

Do I need level shifting between ECU (5 V) and HC-05 (3.3 V)?

Yes. Use a simple 1 kΩ–2 kΩ divider on ECU TX → HC-05 RX, and connect HC-05 TX directly; it has 3.3 V-tolerant inputs. Over-voltage killed one user’s ISA2 RX/TX lines [Elektroda, zbyz, post #17747638]

Is opto-isolation required?

No. Bluetooth already provides galvanic isolation; extra optos add cost and latency. Keep good wiring and a regulator; "there is no point in doing optoisolation" [Elektroda, neo_84, post #18469846]

Can I safely flash ECU firmware over Bluetooth?

Yes, several users updated STAG drivers wirelessly without issues [Elektroda, weryfany, post #19361578] Ensure phone or laptop battery is ≥ 50 % to avoid dropouts; a failed flash can brick the ECU (edge case).

How many connections can the ECU log before locking?

Some non-STAG units count connections and lock when the counter is full, but STAG controllers do not implement this protection [Elektroda, jawa1993, #17741929; weryfany, #17742161].

What’s the current draw of the finished dongle?

HC-05 draws ~30 mA when connected and peaks at 50 mA during discovery [HC-05 datasheet]. A linear 7805 wastes ≈ 0.3 W at 14.4 V, hence the recommendation for a 90 % efficient buck converter [Elektroda, weryfany, post #17747760]

How do I check the required baud rate if I only have a wired cable?

Connect the OEM USB interface, open STAG Gas Synchro, and note the COM port speed shown in the status bar. Use the same rate when programming HC-05 via AT commands [Elektroda, MACIEK_M, post #17770975]

Quick 3-step build recap?

  1. Wire ECU TX/RX/GND to HC-05 through a voltage divider and 5 V regulator.
  2. Enter AT mode, set baud (9600 or 57600) and name/pin.
  3. Enclose in a small remote-key housing and pair with phone/laptop. Build time: under 30 minutes [Elektroda, thread synthesis].
AI summary based on the discussion. May contain errors.
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