UART RX not working on PIC16F1704 - embedded

Question

I have got the UART TX working on one pic but cannot get the UART RX working on another PIC. My plan is to have the first PIC send data to the second PIC.
My initialisation code for the first PIC TX is,
Code:
void configure_TX_port(){
/*Port configurations*/
OSCCON = 0X68;
//Push button
TRISC3 = 1;
INLVLC3 = 0;
ANSC3 = 0;
//Led output
TRISC2 = 0;
//TX output
TRISA2 = 0;
ANSA2 = 0;
/*PPS setup for RA2*/
PPSLOCK = 0x55;
PPSLOCK = 0xAA;
PPSLOCK = 0;
RA2PPS = 0x14;
PPSLOCK = 0x55;
PPSLOCK = 0xAA;
PPSLOCK = 1;
/*UART configuration*/
TXEN = 1;
SYNC = 0;
SPEN = 1;
TXSTA = (0x4|0x20);
SPBRG = (int)(4000000L/(16UL * 9600) -1);
}
My send data to the tx code is
Code:
void putch(unsigned char byte) {
/* output one byte */
while (!TXIF) /* set when register is empty */
TXREG = byte;
}
My initialisation code for the second PIC RX is,
void configure_RX_port(){
/*Port configurations*/
OSCCON = 0X68;
//Led output
TRISC3 = 0;
//RX input
TRISC5 = 1;
ANSC5 = 0;
/*UART configuration*/
CREN = 1;
SYNC = 0;
SPEN = 1;
TXSTA = (0x4|0x20);
RCSTA = 0x90;
SPBRG = (int)(4000000L/(16UL * 9600) -1);
}
My receive data code is,
unsigned char getch(void) {
/* retrieve one byte */
unsigned char ret;
while (!RCIF) { /* set when register is not empty */
}
ret = RCREG;
return ret;
}
When I debug the code the getch function gets blocked waiting on a character but my other PIC is sending data. On this PIC RC5 is a designated RX pin so I dont think I have to do any pps configuration.
Rahul

Answer 1

TX1STA = 0b00100100; This enablex TX (TXEN=1) and high baud rate (BRGH = 1)
RC1STA = 0b10000000; This enable the serial port (SPEN = 1)
The only important missing part is your Clock setting and the baudrate you want to have.
I saw 4000000 in the formula, means 4MHz, and /9600, so assume 9600BDS).
Result = 0x25.
SPBRGL = 0x25;
SPBRGH = 0;
This way, your TX should work. Your tx function is good.
Be sure to configure RX and TX pins as DIGITAL by disabling ANSELA, ANSELB and ANSELC.
Your PIC also use PPS, so be sure to configure it the right way.
*********EDITED POST, RECEIVE CONDITION************
The only difference here to get a working receiver is to enable the continuous receiver
bit, CREN.
RC1STA = 0b10010000; //Enable serial port(SPEN) and continuous receive(CREN).
Be sure to set RX pin (RC5 in your case) as an INPUT (TRISC5 = 1) so that it can read any entering data. You should also consider doing an interrupt routine instead of polling the receiver flag bit. That way you're sure not to skip any entering data.

Answer 2

By default at reset all pins on PIC16F1704 are set as analog.
So clear coresponding bits of RX and TX pins in registers ANSELA, ANSELB and ANSELC to set tham as digital.

Answer 3

You look to be using asynchronous mode with SYNC = 0, but do not set TXEN = 1.
Setting CREN = 1 only overrides TXEN in synchronous mode. Try setting TXEN = 1.

Answer 4

I added the following line, TXSTA = (0x4|0x20); to the receiver PIC code and it works now. There is no need for
CREN = 1;
SYNC = 0;
SPEN = 1;
as its setting the same bits.