Mine is the 35A one here MicoAir743-AIO-35A - Flight Controller - MicoAir Tech. It did come with 4.5.7. Any attempt to reflash fails.
Do you still have the short? Have you tried flashing with stm while in bootloader?
There is a issue when flashing using a USB hub if running Mission Planner. Try flashing direct to the computer. Or use QGC to flash after rebooting to see if that works.
Yes. I held down the boot button on FC, connected directly to the computer. The FC does not even light up. STM Controller GUI does not show it connected or in DFU mode.
@Quadzilla. Thanks for your input. Please see above response.
The FC does not show in Device Manager. That may be the key if anyone can shed light on that please.
Try flashing from DFU Mode with the with_bl.hex target.
MicoAir bl
Hi @dkemxr, hope you are well.
I think I tried it. I held down the boot button on the FC, connected to my laptop. The FC did not show in my device manager on my Windows 11 machine. Usually an FC in DFU shows as such in Device Manager. STM software did not see the FC in DFU mode either.
Did you look under Universal Serial Bus Controllers in Device Manager? Something like “STM device in DFU mode”
Ah well, perhaps you are out of luck then.
@dkemxr - Took your advice. I do see “DFU in FS Mode” under USB Serial Devices (screenshot below)in Device Manager. The board was recognized, screenshot below.
rd.
After flashing, with full chip erase, the same behaviour is observed. Upon connecting the FC to the PC, Device manager shows USB Serial Device (COM10) under Ports(COM&LPT) in Device Manager. AP does not recognize the board. Maybe we are onto something 
Does the board work if You flash again 4.5.7?
I would also try other firmware just to exclude ardrupilot firmware - inav and betaflight have targets for this AIO.
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Just for a quick test try to flash it using QGC.
I’m sure you’ve already seen it but here’s our wiki page for Loading Firmware onto boards without existing ArduPilot firmware
It might be good to try testing with a different PC and/or USB cable.
I wonder if the board doesn’t have the AP bootloader on it
Hello my Audupilot brethren (especially @rmackay9 , @dkemxr , @Quadzilla , @Adam_Borowski ) version 4.7.0 DEV worked!
How did I get there? I went to Micoair site and clicked on this link on the Installing Firmware on MicoAir743 (Ardupilot/PX4/INAV/Betaflight) - MicoAir Tech and following the link for installing AP there browsed to 4.7. DEV version and installed the 4.7.0 version with STM Cube32 programmer.
I have replicated it by installing 4.6.0 stable leading to non-responsive FC behaviour and then installing 4.7.0 DEV making the FC responsive again and connecting to MP normally.
May I request if the required changed is implemented in 4.6.0. Or is it safe to use 4.7.0 please?
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Hi @Asim,
Great that you got 4.7 working! It would be good if we can figure out why 4.6 isn’t working.
There are no significant board specific changes to the MicoAir743 between stable (aka 4.6.0) and latest (aka 4.7.0-dev). This doesn’t mean that there are no code changes though, many things have changed between the two versions. One thing in particular is that we’ve rebuilt the bootloaders for all boards.
To be clear, the two equivalent binaries that should be loaded are the “arducopter_with_bl.hex” files from these two directories
Hi @rmackay9 , imagine my relief!
It is peculiar that 4.5.7 or 4.6.0 is not working for my board. 4.6.0 worked for MicoAir743v2-AIO-45A for @Adam_Borowski as he mentioned that above. Although mine is MicoAir743-AIO.
Yes, the directories that you mentioned above are the ones that I used. Would really like to know the difference and prefer to use the stable version if at all possible.
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I wonder if its related to the bootloader issues
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Hi.
Copter 4.6.0 stable.
With Copter landed, connected to MP, disarmed, showing battery voltage (4S) 14.7V and current 0.4A (5.5A flying), message “Bad battery” is heard every 10s. In MavLink Inspector BATTERY_STATUS:
battery_remaining -1
charge_state: 6
which indicates some kind of confusion.
Changing bits in ARMING_CHECK message “Battery unhealthy” is heard instead.
Main battery parameters:
BATT_MONITOR, 4
(Voltage and current battery pins are assigned and show correct measures)
BATT_CAPACITY, 850
BATT_LOW_VOLT, 14
BATT_CRT_VOLT, 13.8
BATT_FS_VOLTSRC, 1
BATT_FS_CRT_ACT,1
BATT_FS_LOW_ACT,2
BATT_ARM_VOLT,14
MOT_BAT_VOLT_MAX,16.8
MOT_BAT_VOLT_MIN,13.2
In adition, there appear a few “No ap_message for mavlink id (271)” after boot:
Hi @Webillo,
Thanks very much for the report. I’ve added this to the 4.6 issues list.
We have a fix coming in 4.6.2 which will remove the annoying “No ap_message for mavlink id” message.
0.4A seems like a lot for small quad.
These are the correct voltage settings for 4S Lipo:
BATT_ARM_VOLT,14.70
BATT_CRT_VOLT,14.00
BATT_LOW_VOLT,14.40
Set BATT_CAPACITY,0 to see if the problem goes away. You may not need the capacity settings at all. These are the capacity settings for your battery capacity of 850mAhr:
BATT_ARM_MAH,340
BATT_LOW_MAH,255
BATT_CRT_MAH,170
Good. These are other confusing messages on the Messages MP DATA tab:
16/06/2025 13:01:48 : No ap_message for mavlink id (271)
16/06/2025 13:01:34 : Arm: Battery failsafe
16/06/2025 13:01:21 : PreArm: Battery failsafe
16/06/2025 13:01:10 : No ap_message for mavlink id (271)
16/06/2025 13:01:07 : Arm: Battery failsafe
16/06/2025 13:00:50 : PreArm: Battery failsafe
16/06/2025 13:00:42 : Arm: Battery failsafe
16/06/2025 13:00:32 : No ap_message for mavlink id (271)
16/06/2025 13:00:26 : Arm: Battery failsafe
16/06/2025 13:00:19 : PreArm: Battery failsafe
16/06/2025 13:00:06 : Arm: Battery failsafe
16/06/2025 12:59:54 : No ap_message for mavlink id (271)
16/06/2025 12:59:48 : PreArm: Battery failsafe
Let me say that I do two modifications on the sources:
-hwdef.dat: add pin for camera on and off;
-several colors on WS2812 leds.
(BTW, I have to arm manually with MP Actions → Arm).
It would also be great to know the difference between “Bad Battery” and “Battery unhealthy”.
Possibly, I havent’t measured it exactly (it shows 5.5A when flying which also may be inexact). It includes MP+ESC’s, telemetry, display, camera, optical flux+sonar, GPS, 32 WS2812 leds and VTX (which gets hot).
No change: same “Bad battery” every 10s:
No change. I had also tried exagerated high values without success.
Hi @Asim,
I was wonder if you’d be able to try 4.6.1-beta1? This release updates the bootloaders so they should be the same as 4.7.0-dev so if this is the issue it should fix the issue you’ve seen.