help to "Sync" usart

[Rudy_1]

Hi.

Using RF FSK modules with two 16F628, one way link. How may I sync the stream, I mean, send some preamble, like 8 x 0x55, and what?

The problem is that my code only work when i send the code twice.

TX code:

#include <16f628a.h>
#fuses INTRC_IO, WDT, PROTECT, NOBROWNOUT, NOMCLR, CPD, PUT , NOLVP
#use delay(clock=4000000, RESTART_WDT)
#use rs232(baud=2400, xmit=pin_b2, rcv=pin_b1, ERRORS)
#use fast_io(a)
#use fast_io(b)
#byte porta = 0x05
#byte portb = 0x06
#byte txsta = 0x98
#byte rcsta = 0x18
#byte pir1 = 0x0c
#byte pie1 = 0x8c

#bit txen = txsta.5
#bit spen = rcsta.7

#bit up=porta.3
#bit dw=porta.4

int page=0;
int aux_0=0;
int flag_0=0;

#bit deb=flag_0.0

void antideb()
{
aux_0++;
if(aux_0==0xff)deb=0;
}
void tx()
{
output_high(pin_b2);
spen=1;
delay_ms(5);
putc(0x55);
putc(0x55);
putc(0x55);
putc(0x55);
putc(0x55);
putc(0x55);
putc(0x10); // this is what I want, recognizes the 0x10 as unique address.
deb=1;
spen=0;
output_low(pin_b2);
}

Help.

 

[mister_e]

I always suggest to begin with a direct connection first, or at least PIC to PC connection (via MAX232 or else), then add the RF.

We don't see your receiver code yet

 

[Nigel Goodwin]

You can't really send raw serial data over a radio link, unless you have modules with built-in endocders/decoders - the normal method is to use Manchester coding, you can check my tutorial for one method.

 

[Rudy_1]

I already done that, but I think that will be impossible to do something without transmitting and receive the clock too.

I am thinking in use the auxiliary circuit below to get it working properly, don’t see any other choice to send all bits I want. If I use some “specials” radios, the cost will rise too much.

In fact, I will only do one more try, working around a code I got on the web.

#int_RDA
void RDA_isr(void) {
rx_buffer[rx_wr_index] = getc();
rxd = rx_buffer[rx_wr_index]; // this just makes it easier typing-wise later on
rx_wr_index++;
if (rx_wr_index > RX_BUFFER_SIZE) {
rx_wr_index = 0;
}

// now look for unique ID: "Dave "
if (rxd == 'D' && lock_state == 0) {
lock_state++;
}
else if (rxd == 'a' && lock_state == 1) {
lock_state++;
}
else if (rxd == 'v' && lock_state == 2) {
lock_state++;
}
else if (rxd == 'e' && lock_state == 3) {
lock_state++;
}
else if (rxd == ' ' && lock_state == 4) { // got the entire string "Dave ", in that order
lock_state = 0; // reset our "combination lock"
got_id = TRUE;
valid_data_count = 0xff; // get ready to count the number of data bytes - we know we have to expect 5 (Rocks)
// also going to reset the buffer write index back to 0, so that I know where my valid data will be
rx_wr_index = 0;
}
else { // we didn't receive "Dave ", so reset the lock back to the beginning
lock_state = 0;
}

if (got_id && ++valid_data_count == 5) {
data_avail = TRUE;
got_id = FALSE;
}
}

Take a look.

 

[Nigel Goodwin]

I already done that, but I think that will be impossible to do something without transmitting and receive the clock too.

Not at all, why not do like I said, and check my tutorial which shows how it's done - but in assembler, not C.

 

[Rudy_1]

Not at all, why not do like I said, and check my tutorial which shows how it's done - but in assembler, not C.

Ok, where can i found it? I will take alook.

 

[Nigel Goodwin]

Ok, where can i found it? I will take alook.

At the bottom of all my posts in the signature line.

 

[Rudy_1]

My friend, I think you convince me to try a little bit more; of course I will need your help to make some changes in that code for my application.

There are so many times I don’t write in assembly, but this I can fix.
Here are some questions;

1 – FSK modules don´t work? Because I using this ones, RFsolutions is very difficult to me to acquire, I have Phoenix distributor in Brazil, I think they have something near to this modules, but is very expensive.

2 – What tutorial do you think is more “adaptive” to my requirements? My intention is to send about 128bits to air.

3 – For what I saw, the code is sending A/D conversion to air, this is not my intention, once we choose one code for the tutorial list, can you please help me to erase all code regarding to it, I think I can handle this, but just in case, I will need some help.

4 – Like I explained, my intention is to have a LCD, four buttons and nothing more, my C routine will choose some device in my car, by using two of the four buttons, the others two will turn on or off the device I choose before, nothing more, nothing lass then this. How may I send bytes or values between C code and assembly code?

By now I will do compile this two devices in MPlab, verify the hardware you show, and make some tests.

Thanks very very very much for now.

 

[Nigel Goodwin]

My friend, I think you convince me to try a little bit more; of course I will need your help to make some changes in that code for my application.

There are so many times I don’t write in assembly, but this I can fix.
Here are some questions;

1 – FSK modules don´t work?

Of course they work, as long as you use them properly.

2 – What tutorial do you think is more “adaptive” to my requirements? My intention is to send about 128bits to air.

128 bits is a lot of data really, how is that used for your LCD and four buttons?. Obviously it's not a problem, you could either send it as a single packet, or split it into smaller packets.

3 – For what I saw, the code is sending A/D conversion to air, this is not my intention, once we choose one code for the tutorial list, can you please help me to erase all code regarding to it, I think I can handle this, but just in case, I will need some help.

My tutorials just send packets of data, I can't even remember off hand what the exact source of the data was?, but it makes no difference either way.

4 – Like I explained, my intention is to have a LCD, four buttons and nothing more, my C routine will choose some device in my car, by using two of the four buttons, the others two will turn on or off the device I choose before, nothing more, nothing lass then this. How may I send bytes or values between C code and assembly code?

I don't do C, so I've no idea, sorry.

 

[Rudy_1]

Build one example, didn't work.

I will check to see what is wrong.