CH341A programmer view
CH341A back view
CH341A software view

CPU: MIPS (AR9330)
DDR: Zentel
Flash: 8 MB Winbond W25Q64 (original 2M)

git clone https://github.com/pepe2k/u-boot_mod.git u-boot_mod1
wget http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/OpenWrt-Toolchain-ar71xx-for-mips_r2-gcc-4.6-linaro_uClibc-0.9.33.2.tar.bz2

export PATH=$PATH:~/sdb/tmp/u-boot_mod1/OpenWrt-Toolchain-ar71xx-for-mips_r2-gcc-4.6-linaro_uClibc-0.9.33.2/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/bin/
export MAKECMD=make ARCH=mips CROSS_COMPILE=mips-openwrt-linux-
make clean_all
make tp-link_tl-wr740n_v4 IMG_LZMA=1 IMG_SIZE=128
Reference: view

Using CH341A programmer to flash the uboot bin

use open-wrt pre-build image for test
wget http://downloads.openwrt.org/snapshots/trunk/ar71xx/generic/openwrt-ar71xx-generic-tl-wr741nd-v4-squashfs-sysupgrade.bin
mv openwrt-ar71xx-generic-tl-wr741nd-v4-squashfs-sysupgrade.bin a.bin

modify PC ip addr
sudo ifconfig  eth0 192.168.3.51
http://blog.csdn.net/zqixiao_09/article/details/50319877

install tftp server
http://askubuntu.com/questions/201505/how-do-i-install-and-run-a-tftp-server

flash openwrt binary under uboot mode
tftpboot 0x80000000 a.bin
erase 0x9f020000 +0x340004 # 0x340004: size of the a.bin
cp.b 0x80000000 0x9f020000 0x340004 # 0x340004: size of the a.bin

log fragment
Booting image from 0x9F040000...

   Vendor/image name:    OpenWrt 50013
   Hardware ID:          0x7410001
   Whole image size:     3.8 MB (3932160 bytes)
   Kernel size:          1.3 MB (1405180 bytes)
   Rootfs size:          1.9 MB (1990374 bytes)
   Kernel load address:  0x80060000
   Kernel entry point:   0x80060000

   Header CRC...  skipped
   Data CRC...    skipped