经过正点原子的开发板的学习，想自己做一个简单的板子实现自己的一些功能，做好板子后，把芯片和相应的电子零件都焊到板子上，上电后。然后用jlink连接打开jlink软件，居然跳出：info: could not measure total IR len.TDO is constant high.info: could not measure total IR len. TDO is constant high.

No devices found on JTAG chain. Trying to find device on SWD.
No devices found on SWD.
Did not find any core.
Failed to identify target.Trying again with slow (4 Khz) speed.
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
No devices found on JTAG chain.Trying to find device on SWD.
No device found on SWD.
Did not find any core.
No device found at all. Selecting JTAG as default target interface.
我检查了我画的板子上的jlink，线路没有错。为什么插上开发板就正常通讯，插上我自己做的板子就失败，而且跳出上面那一段英文！！
求各位大师，看看是什么问题！！stm32芯片是新买的就焊上去，也不知道，初次用芯片要不要有什么激活之类的！！