Post by thread:RS232

Why is the stop bit necessary? My system reads serial by the following routine, called every 1/baudrate secs. Is active_word flag high? Yes: goto NEXT_BIT START_BIT Look at input line. Is it high? No: Exit routine Yes: Set active_word flag, set rx_bits=no. of bits in word Exit routine NEXT_BIT Look at input line. Shift bit into rx_data store Decrement rx_bits rx_bits=0? No: Exit routine Yes: End of word Clear active_word flag Set received_word flag Exit routine By this method, the next start bit can come immediately after the last data bit. Problems occur if the routine happens to be called on the transition edges of the data. I`m already using the edge trigger bit on RB0 for another serial comms system, and have some maths running "in the background". How can I force it to read the centre of the pulses? Bryan -- spam_OUTb.crotazTakeThisOuTic.ac.uk --------------------------------- TECHNICAL MANAGER Student Television Of Imperial College Beit Quad, Prince Consort Road London SW7 2BB Tel. 0171-594-8104 Fax. 0171-594-8065 Attn. STOIC { NOTE NEW FAX NUMBER }

> Why is the stop bit necessary? > > My system reads serial by the following routine, called every 1/baudrate secs > . > ...... > By this method, the next start bit can come immediately after the last > data bit. Yes, but you can't recover from an error - the stop bit allows you to search for a guaranteed transition when you're out of sync. You still might misinterpret a data transition as the start bit, but you'll soon see another error (a framing error in async nomenclature) and that can cause you to look for a valid stop bit again. Sooner or later, you'll resync correctly. > Problems occur if the routine happens to be called on the transition > edges of the data. I`m already using the edge trigger bit on RB0 for > another serial comms system, and have some maths running "in the > background". How can I force it to read the centre of the pulses? Look for transitions as well as sampling levels - when you detect a transition, rearrange your bit-time timer so that the next level sampled is 1/2 a bit-time later. A more sophisticated algorithm would slide the sample points in response to edge positions (instead of jumping) so that transitions due to noise would cause minimal disturbance to your timing. This is the way hardware UARTs work, often with a counter running at 16x bitrate to define the sample time. The value of the counter is adjusted when a transition occurs to help keep the transitions 1/2 a bit-time away from the sampling point. It's a digital implementation of a phase-locked loop. -adrian

>From: Charles Manning <.....manningcKILLspam@spam@NZ.DIALOGIC.COM> >* Ensuring correct start bit detection. The stop bit is high and the >next start bit is low, thus providing a reliable transition. I just finished my first project on PIC programming, a serial in/out library. During my testing it became apparent to me that my Mac uses a level '1' (-12Volts) as the quiescent RS232 level. Start bits are '0' (12Volt), and the data bit is normal (thus an ASCII 'U' is 01010101, LSB sent first). After that I see a '1' as stop bit, and the line remains at the quiescent level of '1'. Can anyone confirm this? I went ahead and implemented my RS232 to match the above discription, and the routines now work just fine. >From: Bryan Crotaz <b.crotazKILLspamIC.AC.UK> >Problems occur if the routine happens to be called on the transition >edges of the data. I`m already using the edge trigger bit on RB0 for In my system, I setup the RTCC to get me 19,200 interrupts/sec. I am thus able to sample a 9600 bit/sec stream twice per bit. As you pointed out, this may lead to cases where the PIC samples at the transition of a bit. I have not seen this happen during testing. If needed, I can change the routines to three interrupts per bit to guarantee sampling away from an edge. +---------------------------------------+-----------------------------------+ | Edward Cheung, Ph.D. | The opinions expressed herein | |Satellite Servicing Robotics Laboratory| do not necessarily reflect | | NASA Goddard Space Flight Center | those of my employers' | | Code 714.1, Bldg T11B | | | Greenbelt, MD 20771 | | | 301-286-1269(office) 286-1717(fax) | My next book: | | Internet: .....oadebcKILLspam.....robots.gsfc.nasa.gov | Statistics, Demos and Other Lies | +---------------------------------------+-----------------------------------+

> > >From: Charles Manning <EraseMEmanningcspam_OUTTakeThisOuTNZ.DIALOGIC.COM> > >* Ensuring correct start bit detection. The stop bit is high and the > >next start bit is low, thus providing a reliable transition. > > I just finished my first project on PIC programming, a serial in/out > library. During my testing it became apparent to me that my Mac uses > a level '1' (-12Volts) as the quiescent RS232 level. Yup. This is called a mark. It's the idle state for an RS-232 Line. > Start bits are '0' (12Volt), Again correct. > and the data bit is normal (thus an ASCII 'U' is > 01010101, LSB sent first). After that I see a '1' as stop bit, > and the line remains at the quiescent level of '1'. The stop bit it important because if you're sending consecutive characters and the MSB of the first charater is a 0, then there would be no transition between characters. With a stop bit of 1 and and start of 0 a transition is guranteed between characters. > > Can anyone confirm this? Exactly Correct. {Quote hidden}> > I went ahead and implemented my RS232 to match the above discription, > and the routines now work just fine. > > >From: Bryan Crotaz <b.crotazspam_OUTIC.AC.UK> > >Problems occur if the routine happens to be called on the transition > >edges of the data. I`m already using the edge trigger bit on RB0 for > > In my system, I setup the RTCC to get me 19,200 interrupts/sec. I am > thus able to sample a 9600 bit/sec stream twice per bit. As you pointed > out, this may lead to cases where the PIC samples at the transition of > a bit. I have not seen this happen during testing. If needed, I can > change the routines to three interrupts per bit to guarantee sampling > away from an edge. What UART hardware typically does is sample in the middle of the cell only because it's the least likely place to have a transition. My master's student implemented as serial routine set on a 16C84. It works reliably at 19200 and probably could operate at 38400. However it's half duplex only and uses delays instead of the RTCC. It works fine for her applications though. BAJ

petit jc wrote: > > I would like to connect a pic (13c84) to the serial port. > The problem is that I don't want to use any battery and no converter > 0/5v +12v/-12v. > I would like to use the line TX at the level (-12 v) and so I need to > put a regulator between TX and GND. But what about the other lines? How > can I obtain the correct protocol? It seems that a mouse works like that > (TX/GND -12v) but I can't find any schematic of a mouse... > Thanks for response. > KILLspampetitjKILLspamesiee-amiens.fr Hi Jc, I don't know why you want to use the TX insted of RTS. well, this is a circuit that connect to PC via serial port, use no other power supply than the RS-232 and works up to 19200bps. The PIC can receive and transmit data. If you need code, I can send to you, just ask me. Octavio RemoveMEnogueiraTakeThisOuTmandic.com.br list n=78, p=PIC16C84, r=HEX ;*************************************************************************** TITLE "RS232C Interface" ; ; Comments: PIC-16C84/PC RS232 Interface ; By: Terry Rudersdorfer, AScT ; Date: Aug/94 ; Revised: Sep/94 eliminate transistor, diode and resistor on RX ; Revised: Oct/94 added test led for do something test ; ; Fuses: XT or HS and PWRTE enabled ; ; This design provides; ; - full duplex 2400 Baud with 8 bits no parity 1 stop using ; a standard 5.066 MHz communication xtal. ; - only 3 resistors to provide an RS232 Tx/Rx electrical interface ; - power is obtained from the standard RS232 control leads. ; (RS232 O/P's can sink/source 10mA; this circuit uses < 5mA.) ; ; Simple RS232C - PC to PIC Interface Aug/94 T. Rudersdorfer, AScT ; revised Sep/94 ; ; 1 - 470 ohm short circuit current limit ; 1 - 10k open collecter pull down ; 1 - 47k power up pull up ; 1 - 470k injection current limit ; 2 - 15pf oscillator stabilization ; 1 - .1uf decouple PIC and regulator ; 1 - 10uf voltage stabilization ; 1 - 5.0688MHz standard communication xtal ; 1 - 1N4150 reverse voltage blocking diode ; 1 - 78L05 5V low power regulator (100mA Max) ; 1 - 16C84 PIC ; 1 - LED do something test led ; 1 - 2k7 do something current limit for test led ; ; PC DTE DCE ; ; RX<(3)--(3)-/\/\/\/-----------------------------+--/\/\/\/----+ ; 470 | 10k | ; |\ | | /// ; +-----/\/\/\/--| >|---------------------+ | ; | 2k7 |/ | --------------- | | ; | LED | 1 U RA1 |--+ | ; | ^ +5V | RA0 |----+ ; | | | ____ 1 Osc1 |------------------+ ; +---+-/\/\/\/--------| MCLR 6 Osc2 |------+ | ; 47k +-----| Vss C Vdd |--+ | _ | ; | +--| RB0 8 | | +---||_||---+ ; /// | | 4 | | | 5.0688MHz | ; TX>(2)--(2)-/\/\/\/-----+ | | | _|_ _|_ ; 470k |_______________| | ___15pf ___15pf ; | | | ; 1N4150 _____ ^ +5V | /// /// ; |\ | | | | | ; RTS>(4)--(4)-+----| >|----+---|78L05|---+------+ ; | |/ | | 1|_____|3 | ; CTS<(5)--(5)-+ _|_ |2 _|_ ; | ___10uf | ___.1uf ; DSR<(6)--(6)-+ | | | ; /// /// /// ; GND (7)--(7)-+ ; | ; /// ; ; RS232 RX circuit background: ; Based on AN521 in the 1993 Embedded Handbook; PIC I/O pins can handle ; +/- 500uA of continuous injected current. This means voltages greater ; than VDD and VSS CAN BE used as long as adequate current limiting is ; provided. My original RX input design isolated the PIC by using an ; extra transistor, diode and resistor. This can be eliminated by using ; a large enough resistor value in series to the PIC I/O Pin. RS232 ; voltage levels can be up to +/- 15V, therefore, a 470k resistor provides ; an adequate current limit of 32uA (the same current used in AN521). ; ; RS232 TX circuit background: ; Researching specification sheets for RS232 receivers like the 1489, ; reveals that they do not require bipolar voltages to operate. The ; 1489 in fact clips all -ve signals to ground, therefore only requiring ; +ve and ground input levels. ; ;

petit jc wrote: > > I would like to connect a pic (13c84) to the serial port. > The problem is that I don't want to use any battery and no converter > 0/5v +12v/-12v. > I would like to use the line TX at the level (-12 v) and so I need to > put a regulator between TX and GND. But what about the other lines? How > can I obtain the correct protocol? It seems that a mouse works like that > (TX/GND -12v) but I can't find any schematic of a mouse... > Thanks for response. > spamBeGonepetitjspamBeGoneesiee-amiens.fr Hi Jc, I don't know why you want to use the TX insted of RTS. well, this is a circuit that connect to PC via serial port, use no other power supply than the RS-232 and works up to 19200bps. The PIC can receive and transmit data. If you need code, I can send to you, just ask me. Octavio TakeThisOuTnogueiraEraseMEspam_OUTmandic.com.br list n=78, p=PIC16C84, r=HEX ;*************************************************************************** TITLE "RS232C Interface" ; ; Comments: PIC-16C84/PC RS232 Interface ; By: Terry Rudersdorfer, AScT ; Date: Aug/94 ; Revised: Sep/94 eliminate transistor, diode and resistor on RX ; Revised: Oct/94 added test led for do something test ; ; Fuses: XT or HS and PWRTE enabled ; ; This design provides; ; - full duplex 2400 Baud with 8 bits no parity 1 stop using ; a standard 5.066 MHz communication xtal. ; - only 3 resistors to provide an RS232 Tx/Rx electrical interface ; - power is obtained from the standard RS232 control leads. ; (RS232 O/P's can sink/source 10mA; this circuit uses < 5mA.) ; ; Simple RS232C - PC to PIC Interface Aug/94 T. Rudersdorfer, AScT ; revised Sep/94 ; ; 1 - 470 ohm short circuit current limit ; 1 - 10k open collecter pull down ; 1 - 47k power up pull up ; 1 - 470k injection current limit ; 2 - 15pf oscillator stabilization ; 1 - .1uf decouple PIC and regulator ; 1 - 10uf voltage stabilization ; 1 - 5.0688MHz standard communication xtal ; 1 - 1N4150 reverse voltage blocking diode ; 1 - 78L05 5V low power regulator (100mA Max) ; 1 - 16C84 PIC ; 1 - LED do something test led ; 1 - 2k7 do something current limit for test led ; ; PC DTE DCE ; ; RX<(3)--(3)-/\/\/\/-----------------------------+--/\/\/\/----+ ; 470 | 10k | ; |\ | | /// ; +-----/\/\/\/--| >|---------------------+ | ; | 2k7 |/ | --------------- | | ; | LED | 1 U RA1 |--+ | ; | ^ +5V | RA0 |----+ ; | | | ____ 1 Osc1 |------------------+ ; +---+-/\/\/\/--------| MCLR 6 Osc2 |------+ | ; 47k +-----| Vss C Vdd |--+ | _ | ; | +--| RB0 8 | | +---||_||---+ ; /// | | 4 | | | 5.0688MHz | ; TX>(2)--(2)-/\/\/\/-----+ | | | _|_ _|_ ; 470k |_______________| | ___15pf ___15pf ; | | | ; 1N4150 _____ ^ +5V | /// /// ; |\ | | | | | ; RTS>(4)--(4)-+----| >|----+---|78L05|---+------+ ; | |/ | | 1|_____|3 | ; CTS<(5)--(5)-+ _|_ |2 _|_ ; | ___10uf | ___.1uf ; DSR<(6)--(6)-+ | | | ; /// /// /// ; GND (7)--(7)-+ ; | ; /// ; ; RS232 RX circuit background: ; Based on AN521 in the 1993 Embedded Handbook; PIC I/O pins can handle ; +/- 500uA of continuous injected current. This means voltages greater ; than VDD and VSS CAN BE used as long as adequate current limiting is ; provided. My original RX input design isolated the PIC by using an ; extra transistor, diode and resistor. This can be eliminated by using ; a large enough resistor value in series to the PIC I/O Pin. RS232 ; voltage levels can be up to +/- 15V, therefore, a 470k resistor provides ; an adequate current limit of 32uA (the same current used in AN521). ; ; RS232 TX circuit background: ; Researching specification sheets for RS232 receivers like the 1489, ; reveals that they do not require bipolar voltages to operate. The ; 1489 in fact clips all -ve signals to ground, therefore only requiring ; +ve and ground input levels. ; ;

part 0 7114 bytes I send in attach the code I devellop, it is not very well programmed because it was "develloped" same years ago! If you want interrupt driven rotines you will have to use portb (wake-up) and blow up (use) a timer to generate the delays! ; ------------------------------------------- ; pic defs - file:pic16c64.h ; ------------------------------- #define ResetVector 0000h #define IntVector 0004h #define TRUE 1 #define FALSE 0 CBLOCK 0x00 ; Banco 0 indf tmr0 pcl status fsr porta portb portc portd porte pclath intcon pir1 ENDC CBLOCK 0x0E tmr1l tmr1h t1con tmr2 t2con sspbuf sspcon ccpr1l ccpr1h ccp1con ENDC ; CBLOCK 0x81 ; option ; ENDC CBLOCK 0x85 ; Banco 1 trisa trisb trisc trisd trise ENDC CBLOCK 0x8C pie1 ENDC CBLOCK 0x8E ; Banco 1 pcon ENDC CBLOCK 0x92 ; Banco 1 pr2 sspadd sspstat ENDC #define c status,0 #define carry status,0 #define dc status,1 #define z status,2 #define zero status,2 #define rp0 status,5 #define rbif intcon,0 #define intf intcon,1 #define rtif intcon,2 #define rbie intcon,3 #define inte intcon,4 #define rtie intcon,5 #define peie intcon,6 #define gie intcon,7 #define tmr1if pir1,0 #define tmr2if pir1,1 #define ccp1if pir1,2 #define sspif pir1,3 #define pspif pir1,7 #define rtcc tmr0 #define tmr1on t1con,0 #define tmr1ie pie1,0 #define tmr2ie pie1,1 #define ccpie pie1,2 #define sspie pie1,3 #define pspie pie1,7 ;----------------------------------------------- ; File:Com232.h ; Definigues necessarias ao COM232.ASM ;----------------------------------------------- EBaudBit equ 168 ;1/9600 bps=104.166us =>(10+3*x)*200ns=104.166us EBaudSB equ 171 ;(8+3*x)*200ns=104.166us; RBaud equ 169 RBaud05 equ 64 CBLOCK 0x20 Cont Dados DelayCnt Aux ENDC #define Tx porta,0 #define Rx porta,1 #define RxSel porta,2 ; Selecgco de recepgco #define TxSel porta,3 ; Selecgco de transmissco #define CD porta,4 ; carrier detect #define TxPC porta,5 ; Tx e Rx para comunicagco com PC #define RxPC portc,7 ; ; --------------- ; communication rotines ; File: com232.asm ;---------------- ; Necessita de 3 registos : Cont,Dados e DelayCnt ; Invocar ConfigRS232 antes de chamar Enviar ou Receber ConfigRS232 bsf rp0 bcf TxPC bsf RxPC bcf rp0 clrf intcon bsf TxPC ; determina a chegada de mais mensagens bcf tmr1ie ; impede ints do timer 1 bcf tmr1if clrf tmr1h clrf tmr1l clrf t1con return EnviarPC bcf rp0 bcf c movlw 8 movwf Cont bcf TxPC ; Envia Start Bit call EDelaySB ; Espera tempo necessario ao Start Bit EnvSegPC rrf Dados,1 ; Envia 1: LSB btfsc carry ; Verifica se o bit i 1 ou 0 bsf TxPC btfss carry bcf TxPC call EDelayBit ; Espera pelo tempo de 1 bit decfsz Cont,1 ; N: de bits de dados goto EnvSegPC EnvStopPC nop ; acertar tempo 8' bit nop bsf TxPC ; Envia Stop Bit call EDelayBit ; Espera o tempo necess rio return EDelayBit movlw EBaudBit goto EsaveBaud EDelaySB movlw EBaudSB EsaveBaud movwf DelayCnt Erep decfsz DelayCnt,1 goto Erep return ReceberPC bcf rp0 bcf c clrf Dados movlw 8 movwf Cont Receber2PC btfss RxPC ; polling a espera de caracter btfsc RxPC ; start bit i zero goto Receber2PC RecStartPC bcf gie ; impede interrupgues call RDelay05 ; esperar tempo de 1/2 Bit btfsc RxPC ; verificar se e mesmo Start Bit ou goto Receber2PC ; se e ruido RecSegPC call RDelay ; esperar tempo de 1 Bit btfsc RxPC ; verificar se o bit recebido i 1 ou 0 bsf carry ; o bit recebido i 1 btfss RxPC ; verificar se o bit recebido i 1 ou 0 bcf carry ; o bit recebido i 0 rrf Dados,1 ; colocar o bit recebido no byte de dados decfsz Cont,1 goto RecSegPC RecStopPC call RDelay ; esperar tempo de 1 Bit pelo Stop Bit btfss RxPC ; verificar se e o Stop Bit goto ReceberPC ; nao e o Stop Bit. Ha erro! movf Dados,0 ; caracter recebido esta em W e em Dados bsf gie return RDelay05 movlw RBaud05 movwf DelayCnt goto Wait RDelay movlw RBaud movwf DelayCnt Wait decfsz DelayCnt,1 goto Wait return ; -------------------- ; Main loop ; -------------------- LIST p=16C64,r=DEC TITLE "RS-232 ECHO" EXPAND include "pic16c64.h" include "com232.h" ;******* Definigco dos parbmetros RS-232 ******** org ResetVector goto Main org IntVector retfie Main: IFDEF __16C74A ; for 16C74A - porta as I/O digital lines bsf rp0 movlw 7 movwf 09fh bcf rp0 ENDIF call ConfigRS232 ; Sends string "JMC" to PC movlw 'J' movwf Dados call EnviarPC movlw 'M' movwf Dados call EnviarPC movlw 'C' movwf Dados call EnviarPC movlw ' ' Loop: call ReceberPC ; receive from PC call EnviarPC ; echo to PC goto Loop include "com232.asm" end

Hellp Pic'ers. I realise that there has probably been thousands of words on the RS232 subject here in the past. Unfortunatley, I wasn't interested then, but I am now! I've searched the archives for info to no avail. Problem: I want to send a couple of bytes every few minutes for a 16F84 to a Pentium Serial port, and file the bytes. (random access or Sequential - doesn't matter!) (I vagueley remember something about Pentiums giving trouble in this regard) I read up on "Interfacing the Serial Port RS232" by http://www.snet.com.au/~cpeacock, and althoug I understand it, I can;t get it to work. The article uses C as a language, which I know nothing about - I'm a Basic lad. I read Microchips article, "implementation of an Asynchronous Serial I/O, and understood that, but it gave little to the PC end. I thought a null modem setup would work, and wrote (copied) a short routine in QBasic which is supposed to work with Stamps. (I couldn't get it to work with a Stamp either!) VisBasic has serial routines but really, to be honest, it's far to complicated for the job here. Also, to be portable, a VisBasic would need to be "installed" to the host PC. I think my problem is at the PC end. CRO waveforms from the pic look OK. I've checked the routine a million times. I've tried using a MAX 232 and I've tried not using it. It's gotta be the PC end! Questions: Is there a quirk with Pentiums? Should null modem setup work? (one way only - pic to PC) suggested reading? thanks - sorry to be so long winded.

Try Hyperterminal first....split the problem in half, verify that the data being sent is the right baud rate, right voltage levels etc. (if you're sending binary data instead of ASCII data I'd go back to an old DOS terminal program like Qmodem that displays all data in hex :-)) Hopefully someone can suggest a program that works in windoze that us old-timers could upgrade to oneday... Any terminal program should allow you to capture the data and store it to disk. Good luck Howard wrote: {Quote hidden}> Hellp Pic'ers. > I realise that there has probably been thousands of words on the RS232 > subject here in the past. > Unfortunatley, I wasn't interested then, but I am now! > I've searched the archives for info to no avail. > Problem: > I want to send a couple of bytes every few minutes for a 16F84 to a > Pentium Serial port, and file the bytes. (random access or Sequential - > doesn't matter!) (I vagueley remember something about Pentiums giving > trouble in this regard) > I read up on "Interfacing the Serial Port RS232" by > http://www.snet.com.au/~cpeacock, and althoug I understand it, I can;t get it > to work. The article uses C as a language, which I know nothing about - > I'm a Basic lad. I read Microchips article, "implementation of an > Asynchronous Serial I/O, and understood that, but it gave little to the > PC end. > I thought a null modem setup would work, and wrote (copied) a short > routine in QBasic which is supposed to work with Stamps. (I couldn't get > it to work with a Stamp either!) > VisBasic has serial routines but really, to be honest, it's far to > complicated for the job here. Also, to be portable, a VisBasic would > need to be "installed" to the host PC. > I think my problem is at the PC end. CRO waveforms from the pic look > OK. I've checked the routine a million times. I've tried using a MAX > 232 and I've tried not using it. It's gotta be the PC end! > Questions: > Is there a quirk with Pentiums? Should null modem setup work? (one way > only - pic to PC) suggested reading? > thanks - sorry to be so long winded.

Good advice from Ralf. I would also ask, how are you wiring the port? From what you are writing, I suspect that you don't have the handshaking lines wired correctly. When in doubt, on the PC side short: DTR-DSR and CTS-RTS Good luck, myke {Quote hidden}>Try Hyperterminal first....split the problem in half, verify that the data >being sent is the right baud rate, right voltage levels etc. (if you're >sending binary data instead of ASCII data I'd go back to an old DOS terminal >program like Qmodem that displays all data in hex :-)) Hopefully someone >can suggest a program that works in windoze that us old-timers could upgrade >to oneday... > >Any terminal program should allow you to capture the data and store it to >disk. Good luck > >Howard wrote: > >> Hellp Pic'ers. >> I realise that there has probably been thousands of words on the RS232 >> subject here in the past. >> Unfortunatley, I wasn't interested then, but I am now! >> I've searched the archives for info to no avail. >> Problem: >> I want to send a couple of bytes every few minutes for a 16F84 to a >> Pentium Serial port, and file the bytes. (random access or Sequential - >> doesn't matter!) (I vagueley remember something about Pentiums giving >> trouble in this regard) >> I read up on "Interfacing the Serial Port RS232" by >> http://www.snet.com.au/~cpeacock, and althoug I understand it, I can;t get it >> to work. The article uses C as a language, which I know nothing about - >> I'm a Basic lad. I read Microchips article, "implementation of an >> Asynchronous Serial I/O, and understood that, but it gave little to the >> PC end. >> I thought a null modem setup would work, and wrote (copied) a short >> routine in QBasic which is supposed to work with Stamps. (I couldn't get >> it to work with a Stamp either!) >> VisBasic has serial routines but really, to be honest, it's far to >> complicated for the job here. Also, to be portable, a VisBasic would >> need to be "installed" to the host PC. >> I think my problem is at the PC end. CRO waveforms from the pic look >> OK. I've checked the routine a million times. I've tried using a MAX >> 232 and I've tried not using it. It's gotta be the PC end! >> Questions: >> Is there a quirk with Pentiums? Should null modem setup work? (one way >> only - pic to PC) suggested reading? >> thanks - sorry to be so long winded. > > Go on the drive of your life, this week in the book room: http://www.myke.com/Book_Room/book1a.htm Now Available! "Programming and Customizing the 8051 Microcontroller". Find out more at: http://www.myke.com/My_Books/pac8051.htm

myke predko wrote: > > Good advice from Ralf. > > I would also ask, how are you wiring the port? From what you are writing, I > suspect that you don't have the handshaking lines wired correctly. > > When in doubt, on the PC side short: DTR-DSR and CTS-RTS > > Good luck, > > myke > Thanks guys. However....... Hyperterminal!!! Assuming a null modem termination is correct (and I am sure it is) I am a trifle confused with the rate. Bit length = 1 over Baud, result in seconds (Microchip "Implementation of the As Ser I/O) soooo... 2400 Baud = 416uS bit length. Soooo... One second divided by .000416 = 2403. Same same! I always thought, and I may be in error, that a "baud" was a "character" in the old RTTY days. Here it seems "Baud" is "Bits per second" Izzatso? Hyperterminal seems a trifle confused with me too! It seems very interested in "capturing" text to file, or "receivinf a file" (and then asks damn fool questions like what modem protocol I want to use! There ain't no modem, I told it! so, no modem, no protocol, no receiving files, which I OK by me. I want a character at a time!!! I am sending one character (72) which is "H" over and over, with a start bit and a stop bit and idle for a few mS's than start H Stop etc. Should thisn appear on Hypertext (Hypertext?? Hyperterminal!) screen as the character is received, or am I waaaayyyy off the beam. I'd be happy to see a string og H's a string of 72's or anything!!! {Quote hidden}> >Try Hyperterminal first....split the problem in half, verify that the data > >being sent is the right baud rate, right voltage levels etc. (if you're > >sending binary data instead of ASCII data I'd go back to an old DOS terminal > >program like Qmodem that displays all data in hex :-)) Hopefully someone > >can suggest a program that works in windoze that us old-timers could upgrade > >to oneday... > > > >Any terminal program should allow you to capture the data and store it to > >disk. Good luck > > > >Howard wrote: > > > >> Hellp Pic'ers. > >> I realise that there has probably been thousands of words on the RS232 > >> subject here in the past. > >> Unfortunatley, I wasn't interested then, but I am now! > >> I've searched the archives for info to no avail. > >> Problem: > >> I want to send a couple of bytes every few minutes for a 16F84 to a > >> Pentium Serial port, and file the bytes. (random access or Sequential - > >> doesn't matter!) (I vagueley remember something about Pentiums giving > >> trouble in this regard)

<snip> > However....... > Hyperterminal!!! > Assuming a null modem termination is correct (and I am sure it is) > I am a trifle confused with the rate. > Bit length = 1 over Baud, result in seconds (Microchip "Implementation > of the As Ser I/O) soooo... 2400 Baud = 416uS bit length. Soooo... One > second divided by .000416 = 2403. Same same! > Errm it's fairly basic math that 1/(1/X) is going to be X ! > I always thought, and I > may be in error, that a "baud" was a "character" in the old RTTY days. > Here it seems "Baud" is "Bits per second" Izzatso? > In this case Bits Per Second is what is meant. Baud is tricky. Sometimes it's the same as bits per second, sometimes not. It's actually Symbols per second in modem terminology, and a symbol can contain more than 1 bit. {Quote hidden}> Hyperterminal seems a trifle confused with me too! > It seems very interested in "capturing" text to file, or "receivinf a > file" (and then asks damn fool questions like what modem protocol I want > to use! There ain't no modem, I told it! so, no modem, no protocol, no > receiving files, which I OK by me. I want a character at a time!!! > I am sending one character (72) which is "H" over and over, with a start > bit and a stop bit and idle for a few mS's than start H Stop etc. > Should thisn appear on Hypertext (Hypertext?? Hyperterminal!) screen as > the character is received, or am I waaaayyyy off the beam. > I'd be happy to see a string og H's a string of 72's or anything!!! > Hyperterminal is not the most friendly application to use for simple RS232 comms without a modem. It insists on creating a connection profile. The old Win 3.1 terminal was much easier to use. Just make sure that in the setup, you specify "Direct to Comx" where x is the com port you want to use. Click on the configure button and select the desired bit rate and start/stop bits and flow control (probably none for your aplication) and click ok. If you are sending valid RS232 to the correct com port, then characters should start appearing as soon as you click OK. If you want to capture text, all you have to specify is the name of the file you want it written to, no protocols are needed. Unfortunately you can't configure Hyperterminal to display hex so you'll just get a bunch of "H"'s (if it's working). If you need hex code display there are some shareware terminal emulators that may do this. Regards Mike Rigby-Jones RemoveMEmrjonesspam_OUTKILLspamnortelnetworks.com <snip>

Hi Howard, Mike did most of the replies, but I have a couple of comments: >Assuming a null modem termination is correct (and I am sure it is) If it is correct, you should be able to short pins 2 and 3 together and when you send data on the serial port, it should appear on the Hyperterminal screen. If it doesn't, then the handshaking lines are not correct. Ideally, go into "Hyperterminal" Properties and turn off "Handshaking". Before connecting the PICMicro up, make sure you understand what you are doing well enough to be able to loop back characters. <SNIP Bit Rates> >Hyperterminal seems a trifle confused with me too! >It seems very interested in "capturing" text to file, or "receivinf a >file" (and then asks damn fool questions like what modem protocol I want >to use! There ain't no modem, I told it! so, no modem, no protocol, no >receiving files, which I OK by me. I want a character at a time!!! You should start with "Direct" and just go from there. When I create a new one, I use "Direct to Com#" with no handshaking. If you specify anything else, you're gonna get prompted for modem information. >I am sending one character (72) which is "H" over and over, with a start >bit and a stop bit and idle for a few mS's than start H Stop etc. >Should thisn appear on Hypertext (Hypertext?? Hyperterminal!) screen as >the character is received, or am I waaaayyyy off the beam. >I'd be happy to see a string og H's a string of 72's or anything!!! Check the connections and get Hyperterminal working as you would expect. When you are ready for the PC, even if you are sending data incorrectly, you should get something on the screen. Good luck and let me know if you have any more problems, myke This week's books, first find out what I don't like about Michael Eisner's "Work in Progress" and then what I did like about P.T. Deutermann's "Zero Option": http://www.myke.com/Book_Room/book1a.htm Now Available! "Programming and Customizing the 8051 Microcontroller". Find out more at: http://www.myke.com/My_Books/pac8051.htm

If some one need a software there are a shareware in Download.com called Comshow.exe that you can configure to access serial ports and send or recive a word or string of characters .... -----Mensaje original----- De: myke predko <RemoveMEmykeKILLspamPASSPORT.CA> Para: PICLISTSTOPspamspam_OUTMITVMA.MIT.EDU <spamBeGonePICLISTSTOPspamEraseMEMITVMA.MIT.EDU> Fecha: Miircoles, 20 de Enero de 1999 01:19 p.m. Asunto: Re: rs232 >Hi Howard, > >Mike did most of the replies, but I have a couple of comments: > >>Assuming a null modem termination is correct (and I am sure it is) > >If it is correct, you should be able to short pins 2 and 3 together and when {Quote hidden}>you send data on the serial port, it should appear on the Hyperterminal >screen. If it doesn't, then the handshaking lines are not correct. > >Ideally, go into "Hyperterminal" Properties and turn off "Handshaking". > >Before connecting the PICMicro up, make sure you understand what you are >doing well enough to be able to loop back characters. > ><SNIP Bit Rates> > >>Hyperterminal seems a trifle confused with me too! >>It seems very interested in "capturing" text to file, or "receivinf a >>file" (and then asks damn fool questions like what modem protocol I want >>to use! There ain't no modem, I told it! so, no modem, no protocol, no >>receiving files, which I OK by me. I want a character at a time!!! > >You should start with "Direct" and just go from there. When I create a new >one, I use "Direct to Com#" with no handshaking. If you specify anything >else, you're gonna get prompted for modem information. > >>I am sending one character (72) which is "H" over and over, with a start >>bit and a stop bit and idle for a few mS's than start H Stop etc. >>Should thisn appear on Hypertext (Hypertext?? Hyperterminal!) screen as >>the character is received, or am I waaaayyyy off the beam. >>I'd be happy to see a string og H's a string of 72's or anything!!! > >Check the connections and get Hyperterminal working as you would expect. >When you are ready for the PC, even if you are sending data incorrectly, you {Quote hidden}>should get something on the screen. > >Good luck and let me know if you have any more problems, > >myke > >This week's books, first find out what I don't like about Michael Eisner's >"Work in Progress" and then what I did like about P.T. Deutermann's "Zero >Option": > >http://www.myke.com/Book_Room/book1a.htm > >Now Available! "Programming and Customizing the 8051 Microcontroller". >Find out more at: > >http://www.myke.com/My_Books/pac8051.htm