工程师您好：
我们正在使用TMS320C6657开发板进行PC与DSP的串口通信。
运行程序时打印信息显示如下：
[C66xx_0] Initialize DSP main clock = 100.00MHz/1x10 = 1000MHz
Initialize DDR speed = 50.00MHzx26/1 = 1300.000MTS
macaddress: 00:18:30:04:25:23
0183042523
Required baud rate 38400, effective baud rate 39473!
Initialize DDR speed = 50.00MHzx26/1 = 1300.000MTS
macaddress: 00:18:30:04:25:23
0183042523
Required baud rate 38400, effective baud rate 39473!
Test successfully!
Sending packet fail, packetNum = 16
No TX descriptor available, send packet fail
Sending packet fail, packetNum = 16
No TX descriptor available, send packet fail
请问工程师能提供一下C6657的串口通信例程吗？我们目前急需，卡在这个问题上了，希望工程师能尽快帮助我们。谢谢！
Test successfully!
Sending packet fail, packetNum = 16
No TX descriptor available, send packet fail
Sending packet fail, packetNum = 16
No TX descriptor available, send packet fail
