Getting SERIN2 to work?

[BobPigford]

Hello.

This is my first post to this forum. I need help, please.

I have been programming PICs for a few months successfully (turn things on and off, shift out/in, display on LCD, etc). I have a project where I need to convert working BS2 SERIN code to PIC code, so I am using the SERIN2 command for the PIC.
BS2 code is SERIN 16, 16572, [DEC MAX1A]
I know this BS2 code is for 4800 baud, but I want to use 2400 for my PIC project (mode = 16780)

After MUCH trial (and error) over many days, I have NEVER been able to get SERIN2 to accept a string of numbers and place them into a WORD variable. I have tried all manner of combinations to try to get my code to receive a 5 (or fewer) ASCII numeric character string sent from my PC.

Ref: PIC16F876A at 20 Mhz

My PC waits for a "0" from the PIC, then sends the string of numbers.

MAX1A VAR WORD

mainloop:
SEROUT2 TXPin, 16780, ["0"]
SERIN2 RXPin, 16780, [DEC MAX1A]
GOSUB Display
... and do other things then go back around for more input ...
GOTO mainloop

This PIC can receive and send back BYTES to the PC (one at a time) using a BYTE sized variable in the PIC just fine, so I know the baud/word/bit/parity are set correctly.

I know my PC is sending the right characters because I use Serial Monitor software on the PC to watch it.
I see the "0" coming to the PC, then PC sends the string (like "14425" for example), but the PIC never advances beyond the SERIN2 statement. It just hangs there. Note that 14425 is still not larger than a 16-bit integer so it should fit into a WORD sized variable in the PIC. Note also that 14425 should also fit into a 14 bit word.

I have used different variable names, and even array variables without success. Still hangs.

I have even used WAIT (","), and had the PC send the "," prior to the string, but still nothing.

I have used a timeout and label sequence within SERIN2, but it just times out without "seeing" anything from the PC. I have added delays between statements without success. I've tried delays on the PC end., still no luck.
I have made the string followed by a CR,LF characters - still nothing.

There MUST be something FUNDAMENTAL that I do not understand about SERIN2 and WORD sized variables! What do I need to do so that SERIN2 fills the WORD sized variable and does not hang?

PLEASE HELP ME. My frustration level is very high.

Thanks in advance for all suggestions.

Bob Pigford

[Archangel]

Hi Bob,
Welcome to the forum !<br>
Are you sure your PC is sending actual numbers and not ASCII characters ?
I use REAL Term and using it I can select either format. Get it here for free:
http://sourceforge.net/projects/realterm

EDIT: Since I have never bothered to use SERIN2, what I am going to say is purely conjecture on my part.
Serin2 receives 8 bits and an optional parity bit, word is 16 bits so try:


SERIN2 RXPin, 16780, [DEC MAX1A.highbyte,MAX1A.LowByte]

I don't know if it will work, but PBP doesn't choke on it.

[BobPigford]

Thanks Joe S.

It will compile but it hangs up like the other efforts.
I have considered a "resistor problem" and but only 1k receive and 1k transmit resistors work at all (the byte in, byte out test). That also agrees with the manual's recommendation.

I cannot remember being this frustrated in at least 20 years!

Why does it work so easily in a BS2 but seems impossible in a PIC?

Thank you again for your suggestion. I will need all the help I can get.
Bob

[Archangel]

Thanks Joe S.

It will compile but it hangs up like the other efforts.
I have considered a "resistor problem" and but only 1k receive and 1k transmit resistors work at all (the byte in, byte out test). That also agrees with the manual's recommendation.

I cannot remember being this frustrated in at least 20 years!

Why does it work so easily in a BS2 but seems impossible in a PIC?

Thank you again for your suggestion. I will need all the help I can get.
Bob
I always use a max232 between PC and PIC. You might try changing your mode to OPEN INVERTED instead of DRIVEN INVERTED mode 49548.

[mackrackit]

You may want to show your code, the whole code, nothing but the code....well, maybe the configs too. :)

Point is, we do not know what pins you are using or the setup.

You say you are sure the PC is sending because of some program on the PC, have you checked the wires from PC to PIC? Maybe there is a blockage???

Give something like this a try

[mackrackit]

OPPS. I hit submit before I was finished.

Change the code to fit your needs.


SERIN2 PORTB.5,24972,[WAIT("A"),STR NUMS\16] '7, Even

X1 = (NUMS[1]-"0")

X2 = (NUMS[3]-"0")

X3 = (NUMS[5]-"0")

X4 = (NUMS[7]-"0")

X5 = (NUMS[9]-"0")

X6 = (NUMS[11]-"0")

X7 = (NUMS[13]-"0")

X8 = (NUMS[15]-"0")
LCDOUT $FE,1,DEC X1,DEC X2,DEC X3,DEC X4,DEC X5,DEC X6,DEC X7,DEC X8

The above brings the ASC|| data into an array then then does a little parsing.

[Archangel]

Hi Dave,
I think that's what he is hoping to avoid doing, nevertheless it looks as if he will have to. I thought the highbyte / Lowbyte would work for non ASCII numbers though. If i can get some time I am going to play with this a little.

[BobPigford]

Joe S. and mackrackit,
I have some success by going farther back to basics (sending ASCII numbers from a terminal). I'll try to post the code and results later today.
Thank you for your help and patience,
Bob

[BobPigford]

Joe S. and mackrackit,

Background: I had written a program with PBCC (PowerBASIC Console Compiler for WinXP) that:
1) Waits for the PIC to send a "0" to the PC, then
2) the PC sends 12 consecutive 16-bit words to the PIC expecting the PIC to receive them and do other things with them.
I had never been able to get the PIC to receive them. It would always just "hang up" at the SERIN2 statement.

I went back to basics and worked to send a set of characters (numeric) to the PIC via a PC terminal program and had the PIC send them back. I (finally) got it to work just fine:

My TX-RX code for this simple test is:
'--------------------------------------------------------
INCLUDE "MODEDEFS.BAS"

ADCON1 = 7 'set analog pins to digital
TRISA = 1 'set port A to inputs
TRISB = 0 'set port B to outputs
TRISC = 0 'make it an OUTPUT for serial comm on it's pins, even though
'RX is sort of an INPUT.

DEFINE OSC 20

MD VAR WORD
LedPin VAR PORTC.3
RXData VAR WORD
RXPin VAR PORTC.5
TXPin VAR PORTC.4

MD = 16780 '16780 = 2400 driven, 8 bit, 1 stop, no parity, inverted

main:

SERIN2 RXpin, MD, [DEC RXdata] 'waits for a character then moves on

SEROUT2 TXpin, MD, ["I am sending it back -> ", DEC RXdata, 10, 13]

HIGH LedPin 'hook LED to Pin 14 = RC3
PAUSE 20 'a flash of the LED means we got
LOW Ledpin 'this far OK
PAUSE 20

GOTO main
'--------------------------------------------------------

I got this to work with Hyperterm and with a simple terminal program I wrote in PBCC (PowerBASIC Console Compiler for WinXP).
I used a Serial Port Monitor to look at all the bytes going and coming.

What I learned:
1) I need a 1k resistor in the TX line and another 1k resistor in the RX line (I am not using an RS232 converter). Gee, this is exactly what the PBP manual said to do! Other references to a 22k or 10k resistor in the RX line were not good for me. What a wild goose chase that was. It really masked the problem for a long time.
2) The PC transmit end must be set for 8-bit whenever the DEC qualifier is used for variables within the SERIN2 statement. A transmitted 7-bit byte will not do (even though a 7-bit byte can still represents an ascii number).
3) When I use the qualifer DEC, SERIN2 will accept ONLY NUMERIC ascii characters, and it will keep accepting them until any NON-numeric character is received. THIS IS AS IT HAS TO BE. I turns out that my PBCC program had been sending a space character prior to the string of numeric characters. Then DEC caused that variable to be bypassed and nothing was stuffed into that variable at all.
4) The character that tells SERIN2 (with DEC) that the string of numeric characters has ended can be any non-numeric character. It does not have to be a CR.
5) When testing the TX-RX code, remember to send NUMERIC keystrokes in addition to alpha keystrokes. Afterall, wasn't it NUMERIC values I was trying to stuff in there? How could I have missed that one?
6) Breaking my 16-bit value into two bytes (high and low) then sending them to the PIC while SERIN2 uses the DEC qualifier will not work either! That technique must need some other qualifier (or no qualifier ... will have to try that again later).
7) If I set the baud rate mode via a variable, and that mode number is larger than a single byte's worth (like 16780) , then that variable better be defined as a WORD, not as a BYTE. Yet another noobie mistake!
8) SERIN2 is UNFORGIVING and will tell you nothing if:
* DEC is used and if
* Non-numeric STRING characters are sent, or
* If a non-numeric string character is sent
before the numeric string characters are sent.
9) SERIN2 with the DEC qualifier will accept lots of numeric characters, but if they represent a number higher than 65535 (max 16-bit word), the numbers that are stuffed into the variable will not be accurate.
10) While one would think that a Receive pin should be set as an INPUT, no, set both TX and RX pins as outputs. Learned that one by luck.

Now I can even get my 12 word transmission to work with the PIC. Hooray! Now I will move on to making the PIC program do more than receive the needed values. Progress at last!

It has been a painful learning experience. But I am stronger for it, I suppose.
Once I understood it, the PBP manual was right afterall. Ha! How dumb could I be?

Many thanks for your suggestions. One of the reasons I did this long post was to (hopefully) help other beginners navigate around some of these TX/RX and SERIN2 DEC traps.

Best regards to all,
Bob

[Archangel]

My hat's off to you Bob, I don't know where you found that, it's not in the manual that I can find . . . But it works! I've spent 1/2 the night trying to make it work some other way and NADA. You have earned your keep, fixing your own problem . . . Thanks for the lesson !

[BobPigford]

I looked at the resistors that I used successfully. My previous post was in error with regard to the resistor value used in the TX line from the PIC. I used a 10k, not a 1k. I don't know if a 1k will work in the TX line, but I know the 10k works.

I still use the 1k in the RX line to the PIC, though.

I am next going to install an RS232 converter to avoid all this resistor roulette!

Best regards to all,
Bob

[Bronurstomp]

Bob,

I've used the ubiquitous MAX232 to a PC RS232 port with success in an automated tester using Hserin and Hserout. I'm jumping on on this cause I use the PIC16F876A also.
The DB9 on this end is Female so you can use a standard male to female cable to the PC.
Here's some syntax and I'll drop in the related schematic. I have it set at 4800 baud, but I'm sure it'll run much faster. I deleted a bunch of stuff from the diagram, but I left the ISP hookup, as well as the reset button.

This bit of code will wait for *T from the PC, run the TECH subroutine, then after sending the A/D results, waits for 3 numbers, converts them into decimal, uses that for the PWM value, then waits for FN to go on it's way.
The formating stuff in the HSEROUT code is to pad 0s cause the PC (running Labview) was looking for precisely 3 bytes at that point.



DEFINE OSC 8' USE 8MHZ CRYSTAL OSC.
DEFINE ADC_BITS 10' +VREF= 2VDC 1 = .00195V OR ~ 2MV
DEFINE ADC_SAMPLEUS 50' SAMPLE TIME .1MS
DEFINE CCP1_REG PORTC' Hpwm channel 1 pin port
DEFINE CCP1_BIT 2' Hpwm channel 1 pin bit
DEFINE CCP2_REG PORTC' Hpwm channel 2 pin port
DEFINE CCP2_BIT 1' Hpwm channel 2 pin bit
DEFINE HSER_RCSTA 90h' Set RECIEVE Enabled
DEFINE HSER_TXSTA 24h' Set XMIT Enabled HS
DEFINE HSER_BAUD 4800' IL1700 BAUD RATE
DEFINE HSER_CLROERR 1' CLEAR OVER RUN ERRORS
DEFINE CHAR_PACING 1000' CHAR PACING(uSEC) TO 1MS
TRISA=%00001111' SET UP PORTA I/O (1=IN,0=OUT)
TRISB=%11001000' SET UP PORTB I/O
TRISC=%10000000' SET UP PORTC I/O
ADCON1=%10100101' USE PORTA.3 PIN5 AS VREF+ @ 2.0VDC
ADCON0=%01000000' A/D OFF -- RIGHT JUSTIFY. 6MSB=0 ADRESH
HSERIN[WAIT("*"),BUNDONE]
IF BUNDONE = "T" THEN GOTO TECH ' T FOR TECH

TECH:' **************** TECH ************
'
BLEDOUT = 0' TURN BLUE LED ON
HPWM 1, BLUELVL, 5000' CCP1=BLUE SET CURRENT
ADCON0 = %01001101' BLUE ADC
ADCIN 1, BLUSNS' READ IT
BLEDOUT = 1' TURN BLUE OFF
RLEDOUT = 0' TURN RED ON
HPWM 2, REDLVL, 5000' CCP2 =RED SET CURRENT
ADCON0=%01000001' RED A/D
ADCIN 0, REDSNS:REDSNS=REDSNS MIN 999
RLEDOUT = 1' TURN RED OFF
'HPWM 1, 0, 5000' STOP PWM
'HPWM 2, 0, 5000
IF BLUELVL <10 THEN
HSEROUT["00",DEC BLUELVL]:GOTO RED1
ENDIF
IF BLUELVL <100 THEN
HSEROUT["0",DEC BLUELVL]:GOTO RED1
ELSE
HSEROUT [DEC BLUELVL]
ENDIF
GOTO RED1
RED1:
IF REDLVL <10 THEN ' FORMATING
HSEROUT["00",DEC REDLVL]:GOTO BLU1
ENDIF
IF REDLVL <100 THEN
HSEROUT["0",DEC REDLVL]:GOTO BLU1
ELSE
HSEROUT [DEC REDLVL]
ENDIF
GOTO BLU1
BLU1:
IF BLUSNS <10 THEN
HSEROUT["00",DEC BLUSNS]:GOTO RED2
ENDIF
IF BLUSNS <100 THEN
HSEROUT["0",DEC BLUSNS]:GOTO RED2
ELSE
HSEROUT [DEC BLUSNS]
ENDIF
GOTO RED2
RED2:
IF REDSNS <10 THEN
HSEROUT["00",DEC REDSNS]:GOTO WAITF
ENDIF
IF REDSNS <100 THEN
HSEROUT["0",DEC REDSNS]:GOTO WAITF
ELSE
HSEROUT [DEC REDSNS]
ENDIF
GOTO WAITF
WAITF:
HSERIN [WAIT ("F"),EFF]
IF EFF = "N" THEN
GOTO BEGIN
ELSE
GOTO BLULEDSET
ENDIF
GOTO TECH
BLULEDSET:'----------------------SET BLUE--------------------------
HSERIN [WAIT("@"),STR INCOM\3]
INCOM[0] = (INCOM[0]-"0") '
INCOM[1] = (INCOM[1]-"0") ' Convert to decimal
INCOM[2] = (INCOM[2]-"0")
X = 0 ' RESET THE VARIABLE
X = X + INCOM[0] * 100
X = X + INCOM[1] * 10
X = X + INCOM[2]
BLUELVL = (X MIN 255)
X = 0
HPWM 1, BLUELVL, 5000' CCP1 AND SET CURRENT

Then more of the same for the Red channel.
I hope this helps, and I pasted everything correctly!

Bron