自己购买的MK20DX128VFM5芯片没有固件，于是自己就去官网上找了一个固件，通过J-link烧录成功后，再去连接电脑，发现电脑还是不能识别OpenSDA，连上电脑没有任何反应，并没有枚举出USB device，怎么解决，有遇到过类似的情况吗？？？？（PS：MK20DX128VFM5芯片是带有熔丝的，我已经报废了三块芯片了，巨坑。。。。。。。）。下面是我下载的固件（感觉这个BootLoader比较正确）：
前两次我下载的固件是（可能固件不对）：
你好！我的板子型号是IMXRT1052-EVKB, 我是用J Flash工具去烧录的，烧录一次成功后，第二次想再烧录时，就一直连接不上了，无法烧录。第一次烧录的具体步骤：
step1：按住复位键，点击Target ，然后点击连接，第一次是可以正常连接成功的。
step2：按下键盘F3，擦除芯片
step3：按下键盘F5，烧写芯片
step4：烧写成功，拔掉jlink。重新上电，连接电脑，发现电脑还是无法识别OpenSDA。。
下面是我第二次连接时报的一些错误。
Connecting ...
- Connecting via USB to J-Link device 0
- J-Link firmware: J-Link ARM V8 compiled Nov 28 2014 13:44:46
- Device "MK20DX128XXX5 (ALLOW SECURITY)" selected.
- Target interface speed: 4000 kHz (Fixed)
- VTarget = 3.254V
- InitTarget()
- TotalIRLen = 4, IRPrint = 0x01
- JTAG chain detection found 1 devices:
- #0 Id: 0x4BA00477, IRLen: 04, CoreSight JTAG-DP
- Device will be unsecured now.
- Timeout while unsecuring device. Erase never starts.
- TotalIRLen = 4, IRPrint = 0x01
- JTAG chain detection found 1 devices:
- #0 Id: 0x4BA00477, IRLen: 04, CoreSight JTAG-DP
- Scanning AP map to find all available APs
- AP[2]: Stopped AP scan as end of AP map has been reached
- AP[0]: AHB-AP (IDR: 0x24770011)
- AP[1]: JTAG-AP (IDR: 0x001C0000)
- Iterating through AP map to find AHB-AP to use
- AP[0]: Skipped. Invalid implementer code read from CPUIDVal[31:24] = 0x00
- AP[1]: Skipped. Not an AHB-AP
- Scanning AP map to find all available APs
- AP[2]: Stopped AP scan as end of AP map has been reached
- AP[0]: AHB-AP (IDR: 0x24770011)
- AP[1]: JTAG-AP (IDR: 0x001C0000)
- Iterating through AP map to find AHB-AP to use
- AP[0]: Skipped. Invalid implementer code read from CPUIDVal[31:24] = 0x00
- AP[1]: Skipped. Not an AHB-AP
- InitTarget()
- Device will be unsecured now.
- Timeout while unsecuring device. Erase never starts.
- TotalIRLen = 4, IRPrint = 0x01
- JTAG chain detection found 1 devices:
- #0 Id: 0x4BA00477, IRLen: 04, CoreSight JTAG-DP
- ERROR: Could not find core in Coresight setup
- ERROR: Failed to connect.
Could not establish a connection to target.
