# Introduce

This is [ymodem protocal](http://pauillac.inria.fr/~doligez/zmodem/ymodem.txt).
According to it, the sb rb application is realized, which is used to send files and receive files respectively

# Usage

## Common Usage

In the ubuntu system, lszrz needs to be installed, can use `sudo apt install lszrz`.
Use minicom to communicate with the board.


## Advanced Usage

In order to achieve a faster transmission speed,
I added a specific HEADER `STC` to the YMODEM protocol to represent the custom length.
Using the `sb` and `rb` commands on the board, you can use the `-k` option to set the length
of the custom packet, and the unit is KB. Therefore, you need to use `sbrb.py` for file transfer,
and you need `sbrb.py` -k to set the same length as the board. According to my test,
when using -k 32, it can reach 93% of the baud rate,
and is fully compatible with the original ymodem protocol.
First, you need to add a soft link to sbrb.py, for example `sudo ln -s /home/<name>/.../<nuttxwork>/apps/system/ymodem/sbrb.py /usr/bin`
and then sbrb.py can be configured into minicom.`<Ctrl + a> z o` then chose `File transfer protocols` and
crate two option cmd is 'sbrb.py -k 32'. like this

| Name | Program | Name | U/D | FullScr | IO-Red. | Multi |
| ---- | ------- | ---- | --- | ------- | ------- | ----- |
| ymodem-k | sbrb.py -k 32 | Y | U | N | Y | Y |
| ymodem-k | sbrb.py -k 32 | N | D | N | Y | Y |

usb `sb -k 32` or `rb -k 32` for file transfer on board.

## Sendfile to pc

use sb command like this `nsh> sb /tmp/test.c ...`, this command support send multiple files together
then use `<Ctrl + a> , r` chose `ymodem` to receive board file.

## Sendfile to board

use rb cmd like this `nsh> rb`, this command support receive multiple files together
then use `<Ctrl + a> , s` chose `ymodem`, then chose what file need to send.

## help

can use `sb -h` or `rb -h` get help.

# Debug

Because the serial port is used for communication, the log is printed to the debug file
you can use `CONFIG_SYSTEM_YMODEM_DEBUGFILE_PATH` set debug file path.