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temtronic
Joined: 01 Jul 2010
Posts: 9097
Location: Greensville,Ontario
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 Posted: Tue Aug 08, 2017 4:59 am |
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hmm... OK... PIC works, TTLUSB works.
Try the following changes to your program:
| Code: |
#include <16F917.h>
#fuses HS, MCLR, NOWDT, PUT, NOIESO, BROWNOUT, NOFCMEN
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
void main()
{
while(TRUE)
{
printf("\r \n hello");
output_toggle(PIN_D7); //have LED+470R connected here
delay_ms(500); // 1/2 second delay to SEE LED flash
}
}
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With these 2 additions, you should see the LED flash at about a 1 Hz rate AND see hello on the PC screen.
If not
confirm that both RX and gnd of TTLUSB module are connected to PIC
confirm RX of module is connected to PIC TX pin
you can disconnect the TD pin of the TTLUSB module from the PIC,NOT needed and won't work anyway
confirm with scope that 'hello' IS seen on the PIC TX pin when connected to TTLUSB module
One possible problem is that the PC Windows and/terminal program doesn't see the TTLUSB device or it's been assigned to another comport.
If you disconnect the PIC TX and gnd wires, 'loopback' the TTLUSB TXD to RXD pins, evertything typed on the PC KBD should be seen on the PC SCREEN. If not, that's a 'PC problem'.
Jay |
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POPE19
Joined: 27 Jun 2017
Posts: 71
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| Posted: Tue Aug 08, 2017 6:18 am |
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Thank you guys. I am so silly forgot the part that TXD of USB to TTL converter is RX of microcontroller & RXD of USB to TTL converter is TX of microcontroller. I have reversed the pins and i am getting output.
Thanks guys for the help. What a dumb mistake. This cable is working i also check the volts it shows 4.18v at pin C6 & 3.4 at pin C7 of PIC. So it is what temtronic suggested for data transfer as PIC will detect 4v signals.
Just mentioning this so that someone new like me can have reference what might be possibly wrong and troubleshoot reading this post.
Thanks GUYS!! |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Tue Aug 08, 2017 7:04 am |
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Problem is (of course) that the signal may not reach 4.1v reliably at reasonable data rates.
Given the device is 5v 'tolerant', I'd suggest adding a slight pull-up to 5v (perhaps 4K7R, from the incoming data line to 5v). This should not cause any problems, and will help to ensure that the line gets up to 4v more quickly. The internal protection diodes on the USB device will clamp the signal at perhaps 4.1v. In fact the level possibly suggests that the unit already has such a resistor to the USB 5v.
My next suggestion was going to be to put the scope on the pins of the device, and verify which pin actually had data on it, when you sent something from the PC, and then to double check that this was the pin that went to the PIC's RX connection.... |
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