First 64 incoming serial bytes lost after power cycle of Micro:bit

[DeqingSun]

After the power cycle, the first 64 incoming serial bytes get lost. serialRead replied nothing. I've confirmed with a USB analyzer, The second byte of the response to the command 0x83 is always zero with a meanless payload. After the first 64 bytes, things get normal.

Here is how I trigger this bug in Micro:bit:

Using Interface Version: 0253 and hex file https://github.com/microbit-foundation/microbit-firmata/blob/master/precompiled/microbit-firmata-v1.0.hex

Open https://deqingsun.github.io/webUSBTest/stuff/testMicrobitDataBug/web.html in Chrome. Replug Micro:bit. Click "connect", and then click "requestFirmataVersion". The webpage will send F9 00 00 and nRF51 chip replies F9 02 06. The response can be captured on TP15, TGT_TX. But DAPJS can not read anything until the 22nd time you click, and the last 2 bytes are returned.