如下，哪位大侠帮帮忙啊，谢谢了！！！！
[1] Download u-boot or STEPLDR.nb1 or other bootloader to Nand Flash
[2] Download Eboot to Nand Flash
[3] Download Linux Kernel to Nand Flash
[5] Download CRAMFS image to Nand Flash
[6] Download YAFFS image to Nand Flash
[7] Download Program (uCOS-II or TQ2440_Test) to SDRAM and Run it
[8] Boot the system
[9] Format the Nand Flash
[0] Set the boot parameters
[a] Download User Program (eg: uCOS-II or TQ2440_Test)
Download LOGO Picture (.bin) to Nand Flash
[l] Set LCD Parameters
[o] Download u-boot to Nor Flash
[r] Reboot u-boot
[t] Test Linux Image (zImage)
[q] quit from menu
Enter your selection: 7
USB host is connected. Waiting a download.
#mini2440# ：唜xfxx 唜xfxx
问题：
输入的字符如help ，回显都是乱码，如果输入的字符为12345794512 ..................... 之类的回显都是正常的，输入标点符号也是正常的，输入？回车可以看到菜单
请问为什么独独输入英文字符就乱码了呢？请大家帮助一下 ，这个u-boot完全是按照国嵌实验手册修改后编译的 谢谢
