Is there way to tell terminal wait before send more data?

I have embedded firmware which have terminal over serial transmission. I am doing command from terminal which waits data (text file) which it should save to flash chip. However, writing flash is much slower than terminal transmission.

Text file may be pretty big (many kB), so in small embedded environment I cannot simply dump it to RAM. I though if it possible to communicate with standard terminal emulator (which have drag/dop support for files) to pause transmission every time when write buffer is full and tell continue again after write is done? I haven't find anything which may help me throught this.

Well, offcourse I ca开发者_如何学JAVAn make PC frontend which understands this trick, but in basic level it should be nice if all function can be used through normal terminal if needed.

For a basic serial connection you could see if the hardware supports flow control. This would be the CTS, RTS lines (clear to send, request to send).
http://en.wikipedia.org/wiki/RS-232_RTS/CTS#RTS.2FCTS_handshaking

However many simple embedded systems do not implement this type of flow control.

If the hardware does not support flow control, then you will have to look at using some form of software flow control. You maybe able to implement the Xon/Xoff flow control ( http://en.wikipedia.org/wiki/XON/XOFF ) or could implement a simple file transfer protocol, like XMODEM, or ZMODEM, or even tftp. This depends on what your terminal can support.

I always use XMODEM when programming data into FLASH via a serial link from a PC. When using XMODEM it only sends one data packet at a time and waits for you to acknowledge the packet before sending the next one.

This means we control the flow via software on the receiving side:

• Get packet ->
• Write packet ->
• Ack packet ->
• Repeat util done...

XMODEM can be implemented on the smallest of devices (less than 1K RAM) and the code is very simple. All serial terminals support XMODEM (upto windows XP ship with an XMODEM capable terminal). XMODEM requires no special hardware.

Here is the spec.

Here is an example implementation.