关键词：lrzsz、minicom、ZMODEM、MD5sum等。
在环境受限的嵌入式系统上，往往只有串口可以使用。
此时如果需要传输文件，需要借助rz/sz工具，可以使用的传输协议有ZMODEM、YMODEM、XMODEM，一般首选的是ZMODEM。
这里记录minicom下使用rz/sz进行文件传输的操作。
首先说明一下rz和sz的文件传输方向，这些命令都是在调试板上执行的，调试板通过串口和PC相连。
rz表示调试版发起从PC接收文件，sz表示调试版发送向PC传送文件。
1. 使能sz/rz工具
通过buildroot打开Target packages->Networking applications->lrzsz，也即打开了BR2_PACKAGE_LRZSZ。
2. minicom下使用sz/rz工具
2.1 minicom下sz发送文件
首先看一下sz的使用，最简单的就是“sz filename”，传送的文件默认在启动minicom的路径。
如果想指定路径可以通过“sz -f full_path_name”实现，这种方法会在目标板上同样地址保存文件。这样做需要谨慎。
在文件传输结束后，调试版和PC两边通过md5sum验证一下传输数据有效性。
更多使用方法：
sz version 0.12.
Usage: sz [options] file ...
or: sz [options] -{c|i} COMMAND
Send file(s) with ZMODEM/YMODEM/XMODEM protocol
(X) = option applies to XMODEM only
(Y) = option applies to YMODEM only
(Z) = option applies to ZMODEM only
-+, --append append to existing destination file (Z)
-, --twostop use stop bits
-, --try-4k go up to 4K blocksize
--start-4k start with 4K blocksize (doesn't try 8)
-, --try-8k go up to 8K blocksize
--start-8k start with 8K blocksize
-a, --ascii ASCII transfer (change CR/LF to LF)
-b, --binary binary transfer
-B, --bufsize N buffer N bytes (N==auto: buffer whole file)
-c, --command COMMAND execute remote command COMMAND (Z)
-C, --command-tries N try N times to execute a command (Z)
-d, --dot-to-slash change '.' to '/' in pathnames (Y/Z)
--delay-startup N sleep N seconds before doing anything
-e, --escape escape all control characters (Z)
-E, --rename force receiver to rename files it already has
-f, --full-path send full pathname (Y/Z)
-i, --immediate-command CMD send remote CMD, return immediately (Z)
-h, --help print this usage message
-k, --1k send byte packets (X)
-L, --packetlen N limit subpacket length to N bytes (Z)
-l, --framelen N limit frame length to N bytes (l>=L) (Z)
-m, --min-bps N stop transmission if BPS below N
-M, --min-bps-time N for at least N seconds (default: )
-n, --newer send file if source newer (Z)
-N, --newer-or-longer send file if source newer or longer (Z)
-o, ---bit-crc use bit CRC instead of bit CRC (Z)
-O, --disable-timeouts disable timeout code, wait forever
-p, --protect protect existing destination file (Z)
-r, --resume resume interrupted file transfer (Z)
-R, --restricted restricted, more secure mode
-q, --quiet quiet (no progress reports)
-s, --stop-at {HH:MM|+N} stop transmission at HH:MM or in N seconds
--tcp build a TCP connection to transmit files
--tcp-server open socket, wait for connection
-u, --unlink unlink file after transmission
-U, --unrestrict turn off restricted mode (if allowed to)
-v, --verbose be verbose, provide debugging information
-w, --windowsize N Window is N bytes (Z)
-X, --xmodem use XMODEM protocol
-y, --overwrite overwrite existing files
-Y, --overwrite-or-skip overwrite existing files, else skip
--ymodem use YMODEM protocol
-Z, --zmodem use ZMODEM protocol
2.2 minicom下rz接收文件
通过rz接收文件，首先需要输入tz：
然后输入Ctrl+A，紧接着按下Z，在按下S(Send files)。
选择zmodem，进入文件选择界面。
上下键或者PageUp/PageDown移动，空格选择文件。
同样使用md5sum进行验证。
rz version 0.12.
Usage: rz [options] [filename.if.xmodem]
Receive files with ZMODEM/YMODEM/XMODEM protocol
(X) = option applies to XMODEM only
(Y) = option applies to YMODEM only
(Z) = option applies to ZMODEM only
-+, --append append to existing files
-a, --ascii ASCII transfer (change CR/LF to LF)
-b, --binary binary transfer
-B, --bufsize N buffer N bytes (N==auto: buffer whole file)
-c, --with-crc Use bit CRC (X)
-C, --allow-remote-commands allow execution of remote commands (Z)
-D, --null write all received data to /dev/null
--delay-startup N sleep N seconds before doing anything
-e, --escape Escape control characters (Z)
-E, --rename rename any files already existing
--errors N generate CRC error every N bytes (debugging)
-h, --help Help, print this usage message
-m, --min-bps N stop transmission if BPS below N
-M, --min-bps-time N for at least N seconds (default: )
-O, --disable-timeouts disable timeout code, wait forever for data
--o-sync open output file(s) in synchronous write mode
-p, --protect protect existing files
-q, --quiet quiet, no progress reports
-r, --resume try to resume interrupted file transfer (Z)
-R, --restricted restricted, more secure mode
-s, --stop-at {HH:MM|+N} stop transmission at HH:MM or in N seconds
-S, --timesync request remote time (twice: set local time)
--syslog[=off] turn syslog on or off, if possible
-t, --timeout N set timeout to N tenths of a second
-u, --keep-uppercase keep upper case filenames
-U, --unrestrict disable restricted mode (if allowed to)
-v, --verbose be verbose, provide debugging information
-w, --windowsize N Window is N bytes (Z)
-X --xmodem use XMODEM protocol
-y, --overwrite Yes, clobber existing file if any
--ymodem use YMODEM protocol
-Z, --zmodem use ZMODEM protocol