Debug/Serout/Serout2 - please, need advice ...

Hi !
I try to understand how work communication between PIC and PC.
I wrote this simple code :

Code:

---

@ __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON
 
INCLUDE "modedefs.bas"     
DEFINE OSC 04               
        CMCON = 7             
        VRCON = 0             
        WPU = 0                'no wake pullup
        IOCB = 0                'no int. on change
        ANSEL = %01010001     
        ADCON0 = %10000001      'right just , Vref=Vdd , ch.0 , A/D on
        GPIO = %00101001        'preset I/O
        TRISIO = %00001001      'configure direction  1=input 0=output
        OPTION_REG = %10000111

advalue        var    word

Main:
PauseUs 50                  'sample time
        ADCON0.1 = 1                'start A/D
        @ nop
        while ADCON0.1 = 1         
        wend
        advalue.byte1 = ADRESH        'get A/D value
        advalue.byte0 = ADRESL

        if advalue < 650 then
          SerOut2 GPIO.5,300,["Advalue : ",DEC advalue, 13, 10]  ; the calculated result is "93" , but ?!
        endif
goto Main

---

I use on GPIO.0 one 1k resistor to +5 volts and one 100R resistor to ground. Advalue is 93, don't ?!

But on RealTerm I am unable to see the "real" value of Advalue, no matter what option I choose...
What I do wrong ?!
Thanks in advance !

Hi Fratello.

You don't say how your PIC is connected to the PC.
Whether you have the PIC connected via a MAX232 chip or direct to the PC.
e.g.
PIC -> MAX232 -> PC
or
PIC -> PC

It makes a difference on how you use SEROUT or SEROUT2.

Also, take a look in the PBP manual for the SEROUT2 command.
I don't think your MODE setting is quite right for you comms settings on the PC, not to mention what I said above about the connectivity between the PIC and the PC.
If you are trying to use 300 baud 8N1 then setting MODE 300 is most likely not correct.

Read through section 5.73 (SEROUT2 command) and then look at the table in section 8.6 (SERIN2/SEROUT2 Mode List).

With this I think you can find the correct MODE value.

A couple of more suggestions.
1. You have DEFINE OSC 04
I don't know if this is an issue since no errors are reported during compile, but you may want to use DEFINE OSC 4 instead as per the manual.
2. Try a simple program that you just send out a known text string and maybe a value via the serial port without the ADC stuff.
See if you can get just that to work with your PC and then move on to the ADC stuff.

Just some suggestions.

Thanks for reply !
I use simple link PIC to PC (GPIO.5 connected to DB9 - pin 2).
I tried DEBUG command too ... with same results ...
Of course I added in my program :

Code:

---

DEFINE DEBUG_REG GPIO          'Set Debugin pin por
 DEFINE DEBUG_BIT 5            'Set Debug pin bit
 DEFINE DEBUG_BAUD 2400        'Set Debug baud rate
 DEFINE DEBUG_MODE 0            'Set Debug mode: 0=true,1=inverted

---

My schematic is based on Mr.GioppY "serial voltmeter" (http://www.picbasic.co.uk/forum/showthread.php?t=7182) with modification for my purpose ...
Mr.GioppY use, in his program :

Code:

---

debug  dec TmpW dig 4,dec TmpW dig 3,",",dec TmpW dig 2,Cr,Lf

---

but with VB program.
First I tried "Debug DEC Advalue, 13, 10" , but I have same results in RealTerm.

for 2400 baud try mode 16780 for inverted data.
Like Tabsoft suggested, you don’t have a real RS232 serial port there.

SEROUT2 GPIO.5,19697,[ "Hello World !!! ",$D ,$A]

Try the above for 300 baud without a MAX232 chip.

And if that doesn’t work, just get the chip to tell you what it is :D

Code:

---

mode var word
mode = 100;
WHILE mode < 60000
SEROUT2 GPIO.5,mode,[ "    ",DEC mode,"    ", $0D, $0A]
mode = mode + 1;
WEND

---

Interesting project.

I'm no expert on schematics, but something doesn't sit right with the coms section. The 5v logic is used to turn on the 2n3906 via a 4k7 current limiting resistor. To prevent a direct short R10 is used, with R8 restricting the current drawn through the transistor. Normal RS232 ports like to use 12v not 5v as shown, so wondered if this could be part of the problem. But then in the linked post it must of worked for the OP who designed the volt meter ?? uhmm.

Just for clarity, I would get an FTDI based 5v USB to Serial TTL converter, that is seen as a normal com port by the PC and see if that works... If so then the com1 port on the PC is not getting a true voltage and corrupting the system. In the original schematic there is a 20v max line. If this was 12v and the emitter of the transistor was connected to this line than that might work as it's closer to the normal RS232 voltage levels, but then again - I'm no expert and wouldn't want you to damage the PC.

One other thing you can try - check the com setting in the serial capture program and set the flow control to none... I found that with this set to any other option in many serial terminal programs you get garbage displayed on the screen.

Disclaimer: you follow any suggestions at your own risk.

Thanks for support !
The schematic is "valid" since with the original soft works just fine ... When I "give up" to voltage monitor program (VB) I am unable to receive consistent data.

Hey, wasn't being negative....like I stated - I'm no expert... if it works with the original code then the hardware is fine....

You screen shot shows 300 baud, that is why I gave the example that I did.

Now I notice you code a schematic showing 2400 baud.....

RS232 is -12 Volts on the low, so there’s actually 24 Volt difference between one state and another.
I don’t believe it’s possible to do RS232 with any one single transistor if the ground is connected to the other device.

The whole compromise to make 5 Volt RS232 ports is just that.
It could be damaging to connect a real RS232 port to a pic without proper clamping if it didn’t have some awesome IO characteristics.

The RS232 voltage spec:
-3V to -25V = logic 1
+3V to +25V = logic 0


However, if you take a look at a lot of the "MAX232" class chips you'll find that the RXD receiver input has the following characteristics:
Input high threshold: 1.7V (typ), 2.4V (max)
Input low threshold: 0.8V (min), 1.8V (typ)
Input resistance: 3K-7K ohms (pull-down to ground)

Those levels are actually close to what you'd get out of most TTL outputs! It's not "RS232", but you can pretty much drive that directly from a PIC output pin.
I wouldn't do it for a real commercial product, but for a one-of you could probably get away with it.

Connecting to the TXD level from an RS232 output is a different story. There you have to deal with the fact that you might get as much as +/-25V levels on the pin.

Folks don't get distracted by the schematic. This can work with that schematic, or with a piece of wire from pin 2 of the PIC to pin 2 of the DB-9. The transistor and it's support resistors are not really helping anything, but not really hurting either. The problem will be in the code, or possibly a bad PIC. I remember 12 bit cores don't like SEROUT2 but I'm not sure if this device is one of these?

Thanks for support !
As I say the schematic is fine (I think !) : http://www.picbasic.co.uk/forum/showthread.php?t=7182
Just my program is bad ...