lose data when read binary data !

[touchft]

Same problem happens as PR #61 (branch: ams/fix-read-methods). I meet some strange problems. I've made couple tests:

A. send binary data (such .jpg ) to serial A Tx, which connect to serial B Rx
B . send binary data (such .jpg ) to serial A Tx, which connect to serial A Rx
The function readuntil() (read() or nonblocking_read() in branch: ams/fix-read-methods) from Rx port (for both A and B test) will lose one byte every 1023 bytes received, or lose the last byte if I send less than 1024 bytes.

For example, If I send 1024 bytes (raw) to Tx, I got 1023 bytes from Rx port.
If I send 2048 bytes to Tx, I got 2046 bytes from Rx port !
If I send 100 bytes to Tx, I got 99 bytes from Rx port !
This strange problem happens no matter how much baudrate I set, e.g, 115200,921600.
BTW: The software cutecom test binary file send and receive without any problem for above hardware setup !

If I send a pure text file (all ASCII) to Tx, the above problem is gone!

[new test] function sp_blocking_read() : SAME problem: lose one byte every 1023 bytes received, or lose the last byte if less than 1024 bytes was sent !

[touchft]

In fact, when I turn off all flow control, the problem is gone ! When open serial, we has default attributes: RTS SP_RTS_ON and DTR SP_DTR_ON. Use set_flow_control() to turn off these two attributes so that we will remove above problems.

Suggestion: How about we take SP_RTS_OFF and SP_DTR_OFF as default ? Cutecom set these two off as default.