fix: ble write handling

[krushnarout]

Android processes only one ble write at once, that’s why it was crashing

fix: added sequential queue, timeout, and busy error handling

closes #3440

[gemini-code-assist]

Code Review

This pull request introduces a sequential write queue with retry logic to handle BLE write limitations on Android. The implementation correctly serializes write operations and adds robustness with timeouts and exponential backoff for retries. My review includes one suggestion to improve the robustness of the error-checking logic for retries, to avoid potential false positives from a broad string match.

[gemini-code-assist]

The string check msg.contains("201") is a bit fragile and could lead to incorrectly retrying on errors that are not retryable. For example, it could match parts of other numbers in an error message (e.g., a different error code like 1201, or part of a memory address). To make this more robust, consider using a more specific pattern, for example by checking for word boundaries.

Suggested change

	return msg.contains("busy") || msg.contains("201");
	return msg.contains("busy") || RegExp(r'\b201\b').hasMatch(msg);

[beastoin]

where are the tests sir ?

@krushnarout

[krushnarout]

before:

when I try to set the mic gain and dimming frequently

logs:

BLE Transport: Failed to write characteristic: PlatformException(writeCharacteristic, gatt writeCharacteristic() returned 201 : ERROR_GATT_WRITE_REQUEST_BUSY, null, null) 
OmiDeviceConnection: Error setting LED dim ratio: PlatformException(writeCharacteristic, gatt.writeCharacteristic() returned 201 : ERROR_GATT_WRITE_REQUEST_BUSY, null, null)
writeCharacteristic() - prior command is not finished, mClient= 6

Screen.Recording.2025-11-23.at.3.25.22.PM.mov

added two debug prints in ble_transport.dart

after:

here it handling properly

Screen.Recording.2025-11-23.at.9.26.50.PM.mov

@beastoin

[krushnarout]

I found another error, if I try to set the mic gain while the device is disconnected (either out of range or manually turned off)

log:

OmiDeviceConnection: Error setting mic gain: FlutterBluePlusException | writeCharacteristic | android-code: 133 | GATT_ERROR
BLE write attempt #1 to 19b10010-e8f2-537e-4f6c-d104768a1214:19b10012-e8f2-537e-4f6c-d104768a1214 len=1
OmiDeviceConnection: Error setting mic gain: PlatformException(writeCharacteristic, gatt writeCharacteristic() returned 4 : UNKNOWN_BLE_ERROR (4), null, null)

before:

after:

fix: If the device disconnects, all writes stop instantly

Screen.Recording.2025-11-23.at.11.59.08.PM.mov

[aaravgarg]

@beastoin pls review, thanks!

[beastoin]

1/ don't update the state on the writing; whatever the error is, it's not the write func's responsibility.

2/ why do we need to put the writewithoutresponse here https://github.com/BasedHardware/omi/pull/3471/files#diff-9642bdfe5ce0f1472db61c4f7cb153a7b340385781f777a1d674a649eb824333R203-R204?

[krushnarout]

1/ don't update the state on the writing; whatever the error is, it's not the write func's responsibility.

removed

2/ why do we need to put the writewithoutresponse here https://github.com/BasedHardware/omi/pull/3471/files#diff-9642bdfe5ce0f1472db61c4f7cb153a7b340385781f777a1d674a649eb824333R203-R204?

It will choose the fastest supported write mode for the characteristic, when the device allows it for better performance and falling back to normal writes when required. writeWithoutResponse is faster because it avoids waiting