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Joined: 17 May 2005
Posts: 213
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| UART XMIT and RCV? |
 Posted: Fri Oct 20, 2006 8:10 am |
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Hi All
I would like to use the hardware UART for the RCV.
I am using the XMIT hardware pin for something else, so I cannot use it.
I have tried to specify the hardware pin for the RCV and a different pin for the XMIT, but then the RCV interrupt did not work.
Can someone please tell me how to do this? (i.e. have the RCV pin in hardware, while the XMIT pin software driven)?
(Can I simply not use the XMIT pin?)
Thank you
a. |
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Ttelmah
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| Posted: Fri Oct 20, 2006 9:51 am |
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Specify both pins in the #use RS232 setup.
Then just use the transmit pin for your other code.
The 'use' directive, _must_ see both hardware pins, or the hardware UART will not be selected. However once selected, the 'output' code itself, does not get generated, unless you actually 'putc' something to the hardware port, and you can override the tris settings, allowing you to then talk to the pin as normal.
Best Wishes |
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Joined: 17 May 2005
Posts: 213
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| Posted: Fri Oct 20, 2006 10:22 am |
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Hi Ttelmah
Thank you for your reply.
I have set the UART to the hardware pins and it works "fine"- I do get UART interrupts which is great.
However, I use the XMIT pin for something else as well. What I find is that even if I do not use printf, I still get the pin being H. (I do not know if its H all the time, but its used to drive some LEDs and they appear on constatnly- I need them to go H/L periodically).
Any suggestions that you might have will be greately appreciate.
All the best
a. |
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Ttelmah
Guest
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| Posted: Fri Oct 20, 2006 2:56 pm |
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What chip?.
Unfortunately, the way that TRIS behaves with relation to enabling the UART, varies between PICs. On most, if you do an output to the pin, it'll override the UART output. However on some, you have to turn of the transmit component in the UART.
Best Wishes |
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Joined: 17 May 2005
Posts: 213
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| Posted: Fri Oct 20, 2006 11:11 pm |
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Hi Ttelmah
Thank you. Please can you tell me how to be turn on only the RCV portion of the UART (XMIT declared but the pin to be used for something else).
My chip is: PIC16F628A.
I appreciate your help
a |
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Ttelmah
Guest
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| Posted: Sat Oct 21, 2006 2:14 am |
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The 628, should behave normally. It requires TRIS B.2, to be set high, to run as the UART, so as soon as you perform an 'output' instruction on this pin (which will set this bit low), or simply set this bit low with the TRIS statement, the UART should be deselected. However you can disable the transmit part of the UART yourself, with:
| Code: |
#BIT TXEN=0x98.5
//Then in your initialisation code:
TXEN=0;
//Will disable the transmit part of the UART, while leaving the receive
//enabled.
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Best Wishes |
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Joined: 17 May 2005
Posts: 213
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| Posted: Mon Oct 23, 2006 2:15 am |
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Hi Ttelmah
Thank you for your response.
I have the following code pieces:
| Code: |
#use rs232(baud=19200, XMIT=PIN_B2, RCV=PIN_B1, ERRORS)
#byte port_b=6
#bit txen =0x98.5
.........
main(){
txen = 0;
set_tris_b(0B00000010);
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I do get RS232 interrupts- this is great (RCV works).
However, this sets the XMIT pin (B2) H all the time- I have checked this with an O-Scope.
Can you please tell me what I am doing wrong?
Thank you
a. |
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Ttelmah
Guest
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| Posted: Mon Oct 23, 2006 6:44 am |
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Just do 'output_low(PIN_B2)'. This will set the tris automatically, and drive the pin low.
Best Wishes |
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Joined: 17 May 2005
Posts: 213
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| Posted: Tue Oct 24, 2006 8:37 am |
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Hi Ttelmah
I have tried to do the following:
| Code: |
#include <16F628A.h>
#fuses HS, PROTECT, NOWDT, NOLVP, PUT
#use delay(clock=4000000)
#use rs232(baud=19200, xmit=PIN_B2, rcv=PIN_B1,ERRORS)
#byte port_b=6
#bit txen= 0X98.5
main(){
set_tris_b(0B00000010);
port_b=0;
txen=0;
output_low(PIN_B2);
while(true){
}
}
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and the OScope shows that pin_b2 is H all the time!!! (it should be L-right?)
can you please tell me what I am doing wrong?
Thank you for all your help.
a. |
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Ttelmah
Guest
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| Posted: Tue Oct 24, 2006 10:44 am |
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I'd say 'have you got something connected to the pin, stopping it going low'...
Have just tried this code, in a 16F628A, and the pin is low.
Best Wishes |
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Joined: 17 May 2005
Posts: 213
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| Posted: Wed Oct 25, 2006 9:36 am |
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Hi Ttelmah
I have disconnected the PIC16F628A, and put PIN_B2 into Oscope, with the code above, and I once again get a H on it.
I must be doing something wrong. Any suggestions that you might have will be greately appreciated.
Thank you for all your help.
a. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Oct 25, 2006 11:19 am |
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| Post your compiler version and I'll test it. |
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GUEST
Guest
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| Posted: Thu Oct 26, 2006 1:43 am |
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i have same problem and my compiler version is:
pch :3.200
pcm:3.200
pcb :3.200
Thank you for all your help. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Oct 26, 2006 2:12 am |
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Does "Guest" == Arrow ?
Vs. 3.200 is the first version after CCS made some changes to the
compiler. Here is just part of the list of bug fixes that they did soon
after releasing it.
| Quote: |
3.202 A problem with the definition of external ROM is now fixed
3.202 The extra NOP FFFF inserted for some chips is now removed by default
3.202 An optimization bug dealing with the BSR is fixed in the PIC18
3.202 The <<= and >>= operators on the PIC18 with int32's no longer corrupt memory
3.202 The +P command line option was failing on some systems, this is fixed
3.202 SET_PWMx_DUTY broke in 3.200 is now fixed
3.202 Some reported problems with the Bootloader examples are fixed
3.203 Floating point multiply for PIC18 is now much faster
3.203 A bug in 3.202 accessing bit fields in constant structures is fixed
3.203 Some optimization bugs including one involving & is fixed
3.204 Optimization bug from 2.203 is fixed
3.204 Missing nibble on larger addresses in the LST file is fixed |
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Joined: 17 May 2005
Posts: 213
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| Posted: Fri Oct 27, 2006 5:07 am |
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Hi PCM Programmer
"Guest" != arrow
My CCS compiler is: 3.242, and I still have that mysterious problem.
Can you please help me find a "work around"?
Thank you
a. |
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