@PStechPaul:
I compiled your file with MPLAB IDE 5.10 and XC8, BUILD SUCCESSFUL (total time: 657ms), but I can't find .hex file.
In serial.c folder, I don't find it.
Thanks.
 

nidac
@pcbbc:
Please see attached file.
It is very clear that txstr function is wrong.

 
In your pointer version:

RCSTA=0b10010000;

In your printf version:

RCSTA = 0b10000000;

 

REGISTER 10-1:TXSTA: TRANSMIT STATUS AND CONTROL REGISTER (ADDRESS 98h)
bit 4SYNC: USART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode

 
You do understand the difference between synchronous and asynchronous mode and realise that...

SPBRG=25;

...selects completely different baud rates in synchronous vs asynchronous modes?
 

TABLE 10-1:BAUD RATE FORMULA
BRGH = 0 (Low Speed)
SYNC = 0 Asynchronous: Baud Rate = FOSC/(64(X+1))
SYNC = 1 Synchronous: Baud Rate = FOSC/(4(X+1))
BRGH = 1 (High Speed)
SYNC = 0 Asynchronous: Baud Rate = FOSC/(16(X+1))
SYNC = 1 Synchronous: N/A

 
Apologies I didn't spot this earlier.  But in my defence, no one else did either.
 
TBH most of us probably assumed you were following a very basic rule of debugging: Change as little as possible between versions.
 
If you arrive at a solution that works, go backwards until you find the change that broke it.  So if following that mantra, if you suspect a problem with the txstr function, the ONLY thing you should be changing is txstr to printf.  That's clearly not the case with the code you posted.

And lo, the txstr function required zero modification.
So what was the problem?

@PStechPaul:
I compile your code and with xc8 v1.33.

nidac
@pcbbc:
The compiler!?

So your code works regardless of if you set synchronous or asynchronous mode for the serial port, with SPBRG=25?
I highly doubt it.

CREN must be set to receive:

10.2.2 USART ASYNCHRONOUS RECEIVER
...
Once Asynchronous mode is selected, reception is
enabled by setting bit CREN (RCSTA<4>).

@PStechPaul, @ric:
correct.
@pcbbc:
Look at the attached file, it is a code that has printf () and echo simultaneously. The code is compiled with HI-TECH C Compiler v. 7.86 PL3.

@ric:
No, I replay to your post #92.

@ric:
OK