SimHub isn't detecting my Arduino
Last updated · SimHub 9.11.22
If SimHub cannot see your Arduino, work through the causes in this order: a charge-only USB cable (the most common cause by a wide margin), a missing or broken CH340G or FTDI driver, the wrong COM port, SimHub's port scan settings, insufficient 5V power, and finally an unsupported board — the Arduino Uno R4 is explicitly not supported. If the board once worked and now cannot be reprogrammed by SimHub or the Arduino IDE, and Device Manager shows "CH340" rather than "CH340G", you have the generic-chip driver problem, which has its own specific fix.
This is ordered by how often each cause is actually the problem rather than by subsystem, because when your dash has stopped working you want the likely answer first. Roughly the top three account for most cases.
Thirty-second triage
Three questions that split the problem before you change anything:
| Question | If yes | If no |
|---|---|---|
| Does the board's power LED light when plugged in? | It has power. The problem is data — cable, driver or port. | Dead cable, dead port or dead board. Try another USB port first. |
| Does Device Manager show any new device when you plug it in? | Windows sees it. Go to COM port and scan settings. | Windows does not see it. Go to cable and drivers. |
| Did it work before and stop? | Suspect the driver update or a changed COM port. | Suspect the cable, the board type or the wiring. |
Device Manager, quickly. Press Win+X and choose Device Manager. Expand Ports (COM & LPT). Now unplug the Arduino and plug it back in, watching the list — whatever appears and disappears is your board.
1. The cable
This is the single most common cause and it is the one people dismiss fastest, because the board lights up. A charge-only USB cable carries power but not data. The Arduino powers on, its LED glows, and the PC never knows it exists.
Charge-only cables are everywhere: bundled with phone chargers, power banks, USB fans, desk lamps and battery packs. If your Arduino cable came in a box with anything other than an Arduino, assume it is charge-only until proven otherwise.
- How to tell: plug it in and watch Device Manager. If nothing appears or disappears, the cable is not carrying data — or the board is dead, which the next test separates.
- How to prove it: use the same cable with a phone and try to transfer a file. If the phone only charges, the cable is charge-only.
- The fix: use the cable the board came with, or any cable known to sync a phone.
2. Drivers — and the generic CH340G problem
Arduino clones use one of two USB-to-serial chips, and each needs a driver Windows does not always supply.
- CH340G
- On most inexpensive clones. Driver from wch.cn. This is also the chip with the driver problem below.
- FTDI
- On genuine boards and better clones. Driver is
CDM21236_Setup.zipfrom ftdichip.com.
Without the right driver the board appears in Device Manager as an unknown device or under Other devices with a warning triangle, rather than under Ports (COM & LPT). That symptom is diagnostic: Windows can see something is there and does not know what to do with it.
The generic CH340G driver break, in detail
This deserves its own section because it is a distinct failure with a distinct fix, it affects boards that previously worked perfectly, and it is documented on a wiki page that nobody searching for this problem will ever find.
The symptoms are specific. An Arduino that was flashed with the SimHub firmware and worked stops being recognised. It can no longer be reprogrammed — not by SimHub, and not by the Arduino IDE either, which rules out SimHub as the culprit. In Device Manager it identifies as CH340 rather than CH340G.
The cause is a Windows Update driver. Generic CH340G chips are common on inexpensive clones, and a driver update released in late 2023 stopped working with them.
| Version | Date | Status |
|---|---|---|
| 3.5.2019.1 | 30 January 2019 | Known good |
| 3.8.2023.2 | 2 November 2023 | Breaks generic chips |
| Later builds | November 2024 onwards | Second wave of the same problem |
- The easy fix:
FakeCH340DriverFixer, available on GitHub. It installs the 2019 driver, removes the 2023 one, and blocks Windows from silently updating it again through the Windows Update API — that last part matters, because otherwise the problem returns. - The manual fix: disable automatic driver updates, then reinstall CH341SER 3.5.2019.1 by hand.
- Prevention: buy boards from sellers who identify the chip. This is a silicon problem rather than a Windows one — the driver is behaving correctly, it simply does not work with these chips.
Why this is worth checking early despite being unusual. It is the only cause on this page that makes a working setup fail overnight with no change on your part. If your dash worked last week and does not now, and you have not touched the hardware, check the driver version before you touch anything else.
3. The COM port
Windows assigns each serial device a COM number. SimHub has to be pointed at the right one, and there are two traps.
COM1 is almost never your Arduino. The official wiki notes that COM1 is often the motherboard's serial port even on machines with no physical serial connector at all. If you are picking ports by trial and error, COM1 is a red herring that will cost you ten minutes.
The port changed after replugging. Windows can assign a different COM number when you move the board to another USB port, and SimHub does not notice mid-session. Restart SimHub after a port change — this is called out explicitly in the documentation and it is a genuine gotcha, because everything else about the setup looks right.
To find the number: Device Manager → Ports (COM & LPT). Your board will be listed as a USB-SERIAL CH340 or a USB Serial Port with its COM number in brackets.
4. SimHub's scan settings
SimHub's Arduino tab controls how it looks for boards, and the defaults are not always right for a machine with several serial devices on it.
- Scan all serial ports — on by default. Useful, but on a PC with Bluetooth serial ports, a UPS, a 3D printer or a motherboard COM1, scanning everything can mean SimHub gets stuck talking to the wrong thing.
- Excluding ports — telling SimHub to skip the ports you know are not your Arduino is the fix when scanning misbehaves, and it also makes connection noticeably faster.
- Maximum connection attempts — raise it if your board is slow to enumerate; some clones take a moment after power-up.
If you run more than one Arduino, each needs a unique name set during the firmware setup. Two boards with the same name is a configuration that cannot work, and the symptom is one of them never appearing.
5. Something else has the port
A serial port can only be held by one application. If the Arduino IDE's Serial Monitor is open, or a 3D printer host like Pronterface or OctoPrint is running, or another dash application is connected, SimHub cannot open the port and will report the device as missing rather than as busy.
Close everything else that talks to serial hardware, then restart SimHub. This is quick to test and easy to overlook, especially right after flashing, when the IDE is still open from the upload.
6. Power
A USB port supplies about 500mA. An Arduino on its own is well inside that; an Arduino driving a strip of addressable LEDs is not. Past that limit the board browns out, resets in a loop, or enumerates and then drops off — which reads as an intermittent detection problem rather than a power problem.
The fix is an external 5V supply, and the wiring detail matters:
Connect the grounds, not the 5V. Connect the external supply's ground to the components and to the Arduino, but do not connect the external 5V to the Arduino's 5V pin. This is stated explicitly in the official wiring guidance, and getting it wrong is a good way to damage the board.
Also worth knowing, because it accounts for a surprising share of "random" disconnects: the official wiki states plainly that most Arduino disconnects and display errors are caused by bad quality solder joints. If your problem is intermittent and moves when you wiggle the wiring, it is the wiring.
7. The board is not supported
SimHub's firmware targets a specific set of boards. Others may power on and appear in Device Manager and still never work.
| Board | Status | Notes |
|---|---|---|
| Arduino UNO R3, and clones | Supported | The default choice |
| Arduino NANO v3 (ATmega328), and clones | Supported | Small, cheap, common |
| Arduino MEGA (ATmega2560), and clones | Supported | Use when you need many pins |
| Arduino Pro MICRO 5V/16MHz | Supported, with limits | Reduced feature support — library incompatibility affects tachometer support. Required for gamepad features. |
| Arduino Leonardo, and clones | Supported, with limits | As Pro Micro |
| Arduino UNO R4 | Not supported | Explicitly stated. A newer board number is not a newer version of a supported board. |
| ATmega168p | Avoid | Sometimes sold on misleadingly labelled "Arduino Nano" boards |
| WAVGAT-branded boards | Avoid | Described in the official wiki as fake Arduinos with fake or wrong chips |
On ESP32 and ESP8266, which you will see recommended. Official SimHub firmware does not support ESP boards. Separately, a third-party community firmware called ESP-SimHub does exist and does work with them. Both statements are true, and confusing the two is why you will find guides confidently telling you an ESP32 works out of the box. It does not — you need the community firmware, which is a different project with its own support channel.
8. USB hubs
Unpowered hubs make the power problem worse and add a layer of enumeration that some clones do not survive. If you are going through a hub, plug directly into the PC to test — this takes ten seconds and eliminates a whole class of cause.
Front-panel USB ports on desktop cases are also worth stepping around during diagnosis; they are wired through an internal header and are more prone to marginal connections than the ports on the motherboard's back panel.
If none of that worked
At this point the useful thing is to separate SimHub from the hardware entirely. Install the Arduino IDE and try to upload the blink example to the board.
- The IDE uploads successfully — the board, cable, driver and port are all fine, and the problem is in SimHub's configuration. Revisit scan settings and device naming.
- The IDE also cannot see it — the problem is below SimHub. Cable, driver or board, in that order. If it is a CH340 board that used to work, the generic-chip driver break above is the strong favourite.
One last note on flashing, because it is destructive and irreversible: always confirm the serial port belongs to the device you mean to flash. Unplug every other Arduino first. Wiping the firmware of the wrong device cannot be undone.
If you have one of our displays, it ships already flashed — it should appear as a normal CH340 serial device with no firmware step needed at all, so a detection problem on ours is a cable, driver or port problem rather than a firmware one.
Common questions
Why does SimHub see my Arduino sometimes but not always?
Intermittent detection is nearly always physical: a marginal cable, a bad solder joint, or a board browning out because it is drawing more than the USB port's 500mA. The official wiki is blunt that most Arduino disconnects come from poor solder quality. If wiggling the wiring changes anything, that is your answer.
Does the Arduino Uno R4 work with SimHub?
No. The Uno R4 is explicitly not supported. Use an Uno R3, a Nano v3, a Mega, a Pro Micro 5V/16MHz or a Leonardo. A higher board number is not a newer version of a supported board — the R4 uses a different microcontroller architecture entirely.
Can I use an ESP32 or ESP8266 with SimHub?
Not with official SimHub firmware, which does not support them. A separate community project called ESP-SimHub provides ESP32/ESP8266 firmware that works with SimHub, and it is a real and maintained thing — but it is a third-party project with its own support channel, not a SimHub feature. Guides that say ESP32 works out of the box are conflating the two.
My Arduino shows as CH340 instead of CH340G. What does that mean?
It means you have a generic CH340G chip and Windows has installed the driver that breaks it — version 3.8.2023.2 from November 2023 or later. Roll back to CH341SER 3.5.2019.1, ideally using the FakeCH340DriverFixer tool, which also blocks Windows from updating it again.
I changed USB ports and now SimHub can't find it.
Windows may have assigned a different COM number, and SimHub does not pick that up mid-session. Restart SimHub. If it still cannot find it, check Device Manager for the new COM number and check that port is not excluded in SimHub's scan settings.
Do I need to flash the Arduino before SimHub will see it?
SimHub can detect an unflashed board well enough to flash it, so detection should not require firmware. If SimHub cannot see the board at all, the problem is below the firmware layer — cable, driver, port or board type.
Can two Arduinos work with SimHub at once?
Yes, and it is common — one for LEDs, another for a display. Each must be given a unique name during firmware setup. Two boards sharing a name is a configuration that cannot work, and the usual symptom is that only one of them ever appears.
Sources
Related guides
- Troubleshooting hubThe decision tree for every other symptom — game not detected, silent shakers, dashboards lagging.
- Arduino setup, step by stepThe firmware wizard from launch to upload, including the pin-collision rule that stops builds.
- Arduino hubSupported boards, wiring, power and what SimHub can drive from them.
SimHub is developed independently by Wotever and is not affiliated with oesimracing. This page was checked against SimHub 9.11.22 on 4 August 2026; where the interface has moved on since, the version stamp tells you how far. More on what SimHub is and what it costs.