I have an HM-10 BLE module connected to Arduino Leonardo. It forwards UART from my computer:

#define btSerial Serial1

void setup() {

    while (!Serial) {

    Serial.println("Initialized on 9600");

    while (!btSerial) {

    Serial.println("BT initialized on 9600");

void loop() {
    if (btSerial.available()) {

    if (Serial.available()) {

In general, it works fine, but I've decided to flash it and sent AT+SBLUP command to it, and it's in flash mode now.

Later I've realized that I can't flash it because Parallels Desktop's COM forwarding does not work fine (I work on macOS).

And now I can't quit from the flash mode — it just does not respond to AT commands (however, btSerial is alive).

I've tried to reset the Arduino, disconnect BT for several minutes — it's still in flash mode. How to quit this mode?

  • 1
    you must flash some firmware
    – Juraj
    Commented Jan 18, 2020 at 18:46
  • 1
    If you disconnected power from the HM-01 and it's still in flash mode the next time you power it, I would guess, that entering flash mode erases the firmware. Thus you would have to burn a new firmware to it. But thats just a guess
    – chrisl
    Commented Jan 18, 2020 at 19:32


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