Problem with rs-232 port ?

[elMickotanko]

Hi,

I have a problem with my serial PIC programmer. When I hit "write" to program a chip it gives me the error message:

"No pic on board / PIC not supported"

Its a velleman kit (has buttons and LEDs for testing). I have tried a couple of chips. The test mode works for an already programmed chip (press a button to light an LED etc). I havent used the board in a while but the last time it worked fine.

Ive checked some continuity on the board and cant spot anything wrong. The cable is definetly fine.

I checked the pins on my PCs com1 port (9-pin D-type) -
PINS 3,4,5 and 7 are connected to the metal shielding (grounded).

Is this the problem?? Or are they just 'tied' to ground when the port isnt being used. Is there anything else i should check?

Can any1 help. This is really frustrating as i just finished building the LCD board for Nigels third tutorial!

Thanks,
M!C/<

 

[eblc1388]

I checked the pins on my PCs com1 port (9-pin D-type) -
PINS 3,4,5 and 7 are connected to the metal shielding (grounded).

Try testing a normal resistor to confirm the ohmmeter is OK in the first place.

PC 9-pin D Serial com port:
==================
pin 3: TD
pin 4: DTR
pin 5: GND
pin 7: RTS

So if pin3, 4 and 7 all shorted to ground, then there is something wrong with the port. Are sure you are looking at a COM port? Or your PC motherboard is an ASUS board?

The worst is that the IC inside the computer providing the port is dead. Double check the ohms reading with the PC powered OFF (plug removed from AC socket).

 

[elMickotanko]

if pin3, 4 and 7 all shorted to ground, then there is something wrong with the port. Are sure you are looking at a COM port? Or your PC motherboard is an ASUS board?

Yep the multimeter is ok.

Yes, it is an Asus board (a7n266-vm). What does this mean??

The worst is that the IC inside the computer providing the port is dead. Double check the ohms reading with the PC powered OFF (plug removed from AC socket).

Ah, They're not shorted to ground when plug is removed (except pin5 obviously) As soon as I plug the power back in, theyre grounded again.

Now what do I do?

Thanks very much for your reply

 

[eblc1388]

The mentioning of ASUS is that some motherboards made in 2001 & 2002 (mine TUSL2-C for example) has bad noise bypass capacitors on signal lines of ports. But the symptoms would not go away with power off.

With respect to your case, I would recommend you measure the voltages instead of resistance during PC powered ON. Resistance measurement is largely affected by voltages on the port pins so is not accurate.

Power ON the PC and let it boots. Then put black multimeter probe to case/ground and measure voltage of each port pin. The should have voltages anywhere between +/- 12V. Note: some port pins might give you -ve polarity so you would have to reverse the probes to get a reading. Then do the measurement again with a resistor(1,000 ohms to 2000 ohms, doesn't matter) across the multimeter leads to act as loading.

Post the two sets of results here and let's see if we can spot any problem.

 

[elMickotanko]

pin V(no load) V(1k load)

1 .... 0.15 .... 0.02
2 .... 0.15 .... 0.02
3 .... -11.38 .... -7.77
4 .... -11.38 .... -7.77
5 .... 0 .... 0
6 .... 0.15 .... 0.02
7 .... -11.38 .... -7.77
8 .... 0.15 .... 0.02
9 .... 0.15 .... 0.02

Sorry its not very neat, the message box doesnt seem to recognise spaces.
Cheers

 

[Nigel Goodwin]

Sorry its not very neat, the message box doesnt seem to recognise spaces.

HTML doesn't do spaces! - you should click on the Code button before and after your listing, this prevents your browser ruining the formatting.

 

[elMickotanko]

pin    V(no load)   V(1k load)

1         0.15            0.02
2         0.15            0.02 
3         -11.38         -7.77
4         -11.38         -7.77
5         0                0
6         0.15            0.02
7         -11.38         -7.77
8         0.15            0.02
9         0.15            0.02

Cheers!

 

[eblc1388]

I did the same checks on my PC serial port.

All readings are within 5% that of yours. So I can only say your PC serial port looks fine.

The problem is elsewhere.

 

[mechie]

I havent used the board in a while but the last time it worked fine.

Is it possible you have the wrong serial lead ?
They come in two flavours; straight (pin to pin) and Null Modem (pins 2 and 3 cross over, as do a few others).

If you have the wrong one then your software should report exactly the same fault as when the lead is unplugged.

Just a guess ...

 

[eblc1388]

Is your programmer looks like this one? Model K-8048?

If so, beware that the toggle switch on board is a three position switch. The middle position is standby and do nothing. The crystal should NOT be connected to the PIC while programming. i.e. remove the jumper.

 

[elMickotanko]

Is your programmer looks like this one? Model K-8048?

If so, beware that the toggle switch on board is a three position switch. The middle position is standby and do nothing. The crystal should NOT be connected to the PIC while programming. i.e. remove the jumper.

Yep, thats the one. I took of the jumpers ... AND IT WORKS!!!

Thanks very much, im such an idiot, i should have thought of that.

I can get on with the LCD tutorial now!

Thanks for your time, checking your serial port etc.

M!C/<

 

[TomS]

Hi,

I have the exact same problem the OP had originally. Im using the serial cable that came with the PIC programmer kit, but when I try to write I get "No PIC on board".

Ive tried taking the jumpers off the board as suggested, but still no luck. Ive also downloaded the latest version of the software from Vellemans website, still nothing.

Does anyone have any further ideas?

Im using a Dell laptop (Inspiron 8500) if that helps.

Cheers!

p.s. sorry for draggin up an old topic.

 

[TomS]

Ok, interestingly enough, if I try to program the PIC from my Dell Inspiron 8100 it works

No problems afterall it would seem

 

[twinklu7]

Hi,
I am a newbie ..i am interfacing MCU atmega8l to PC through RS232 ,here i did the loop back test via hyperterminal i didn't get the response from the MCU.
And before communicating to mcu i did the loop back test to the following for these i got the response

Start from the cable and work you way over to the PIC. Use hypertem to do a loopback in each of the following steps. I understand that step 1 will pass and step 4 will fail in your case.

1. Remove the RS232 cable from the Inchworm and short pins 2 and 3 on the cable.

2. If step 1 passed: Remove the MAX232. Look at the schematic and determine which pins on the MAX232 socket connect to 2 and 3 on the DB9. Short these pins at the MAX232 socket. If this works you know the RS232 signal is getting to the MAX232. If not you have bad solder joints between the DB9 and the MAX232 socket.

3. If step 2 passed: Replace the MAX232 and remove the PIC. Short the MAX232 pins that go to TX and RX on the PIC at the MAX232 chip. If this works your MAX232 is working.

and here the 4 th step i tried but i am not able to identify where my communication pbm is?So i need some assitance

4. If step 3 passed: Short the TX and RX pins on the PIC. If this fails you have bad solder joints between the MAX232 and the PIC.

Please would anybody try to help out..

 

[twinklu7]

problem from MCU ATMEGA8L TO PC THROUGH RS232

Hi,
I am a newbie ..i am interfacing MCU atmega8l to PC through RS232 ,here i did the loop back test via hyperterminal i didn't get the response from the MCU.
And before communicating to mcu i did the loop back test to the following for these i got the response

Start from the cable and work you way over to the PIC. Use hypertem to do a loopback in each of the following steps. I understand that step 1 will pass and step 4 will fail in your case.

1. Remove the RS232 cable from the Inchworm and short pins 2 and 3 on the cable.

2. If step 1 passed: Remove the MAX232. Look at the schematic and determine which pins on the MAX232 socket connect to 2 and 3 on the DB9. Short these pins at the MAX232 socket. If this works you know the RS232 signal is getting to the MAX232. If not you have bad solder joints between the DB9 and the MAX232 socket.

3. If step 2 passed: Replace the MAX232 and remove the PIC. Short the MAX232 pins that go to TX and RX on the PIC at the MAX232 chip. If this works your MAX232 is working.

and here the 4 th step i tried but i am not able to identify where my communication pbm is?So i need some assitance

4. If step 3 passed: Short the TX and RX pins on the PIC. If this fails you have bad solder joints between the MAX232 and the PIC.

Please would anybody try to help out..