Post by thread:Re: PC Hardware (again)

Andy, if you want to take over the PC's serial port in a `non-multitasking-friendly' manner, here is a C `snippet' that I use: >From the header file: --------------------- /* Type Definitions */ typedef unsigned char UBYTE; /* Old habbit... */ ... /* Serial Port Definitions */ #define COM1_BASE 0x3F8 /* COM1 Base Address */ #define COM2_BASE 0x2F8 /* COM2 Base Address */ #define COM3_BASE 0x3E8 /* COM3 Base Address */ #define COM4_BASE 0x2E8 /* COM4 Base Address */ #define COM_BASE COM2_BASE /* COM Base Address */ /* Function Prototypes */ void InitUSART(void); /* Initialize USART */ void TxData(UBYTE); /* Transmit Data */ UBYTE RxData(void); /* Receive Data */ ... >From the application file: -------------------------- Note, there are a lot of ways to do this. I use these routines as a generic package and add sections relating to CTS/RTS and DTR/DSR as needed. Also, they do not provide a time-out for a port that is not responding nor do they use interrupts. I've used them up to 115.2K with handshaking disabled. Works fine with a 20MHz PIC16C76/77 at 115.2K. (BRGH = 1, SPBRG = 10). This is also the interface to my weather station and my PIC-based logic analyzer which is in the prototype stage. /* InitUSART() - Initialize USART to 115200, 8 Data Bits, No Parity, 1 Stop Bit */ void InitUSART(void) { outp(COM_BASE + 1, 0x00); /* Turn off interrupts */ outp(COM_BASE + 3, 0x83); /* Access Divisor Latch */ outp(COM_BASE + 0, 0x01); /* Set 115200 (115200/1) Baud */ outp(COM_BASE + 1, 0x00); outp(COM_BASE + 3, 0x03); /* Access DFM reg. Configure Data Format */ outp(COM_BASE + 4, 0x03); /* Disable Loop, !OUTx. Enable !RTS, !DTR */ } /* TxData() - Send Data to Serial Port Entry: data = Data to transmit */ void TxData(UBYTE data) { UBYTE x; do /* Check for Tx Buffer Empty */ { x = inp(COM_BASE + 5); x &= 0x20; } while(x == 0); outp(COM_BASE + 0, data); /* Send Data */ } /* RxData() - Receive Data from the Serial Port Exit: data = Rx Data */ UBYTE RxData(void) { UBYTE x, data; while(TRUE) /* Check for Rx Data */ { x = inp(COM_BASE + 5); x &= 0x01; if(x == 1) { data = inp(COM_BASE + 0); /* Get Data */ break; } if(kbhit()) /* Abort if Keypress */ { getch(); printf("\n"); break; } } return(data); } For Handshaking, I use the following: /* Wait for !CTS */ do { x = inp(COM_BASE + 6); x &= 0x10; } while(x == 0); /* Wait for !DSR */ do { x = inp(COM_BASE + 6); x &= 0x20; } while(x == 0); /* Wait for !RI */ do { x = inp(COM_BASE + 6); x &= 0x40; } while(x == 0); /* Wait for !DCD */ do { x = inp(COM_BASE + 6); x &= 0x80; } while(x == 0); /* Disable !RTS */ x = inp(COM_BASE + 4); x &= 0xFD; outp(COM_BASE + 4, x); /* Enable !RTS */ x = inp(COM_BASE + 4); x |= 0x02; outp(COM_BASE + 4, x); /* Disable !DTR */ x = inp(COM_BASE + 4); x &= 0xFE; outp(COM_BASE + 4, x); /* Enable !DTR */ x = inp(COM_BASE + 4); x |= 0x01; outp(COM_BASE + 4, x); - Tom At 10:37 AM 12/29/98 -0500, Andy Kunz wrote: {Quote hidden}>How do I tell teh UART in a PC to speak even though the modem/handshake >lines tell it not to? > >It looks like THAT is more of a problem than the IRQs were :-( > >Andy > >================================================================== >Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA >================================================================== > >

>From spam_OUTowner-piclistTakeThisOuTmitvma.mit.edu Tue Dec 29 15:27:17 1998 >Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by walnut-backup.ease.lsoft.com (LSMTP for OpenVMS v1.1b) with SMTP id <.....1.0001CB40KILLspam@spam@walnut-backup.ease.lsoft.com>; Tue, 29 Dec 1998 13:51:39 -0400 >Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV release 1.8c) with > NJE id 0131 for PICLISTKILLspamMITVMA.MIT.EDU; Tue, 29 Dec 1998 13:57:26 > -0500 >Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail > V1.2b/1.8b) with BSMTP id 9777; Tue, 29 Dec 1998 13:57:08 -0500 >Received: from ha1.rdc1.sdca.home.com [24.0.3.66] by mitvma.mit.edu (IBM VM > SMTP V2R4a) via TCP with SMTP ; Tue, 29 Dec 1998 13:57:07 EST >X-Warning: mitvma.mit.edu: Host ha1.rdc1.sdca.home.com claimed to be > mail.rdc1.sdca.home.com >Received: from cx48592-a ([24.4.88.50]) by mail.rdc1.sdca.home.com (InterMail > v4.0 201-221-107) with SMTP id > <19981229185657.YKKM29537.mail.rdc1.sdca.home.com@cx48592-a> for > <.....PICLISTKILLspam.....MITVMA.MIT.EDU>; Tue, 29 Dec 1998 10:56:57 -0800 >X-Sender: lists@mail >X-Mailer: QUALCOMM Windows Eudora Pro Version 4.1 >Mime-Version: 1.0 >Content-Type: text/plain; charset="us-ascii" >Message-ID: <4.1.19981229104948.0094e3b0@mail> >Date: Tue, 29 Dec 1998 10:56:33 -0800 >Reply-To: pic microcontroller discussion list <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU> >Sender: pic microcontroller discussion list <PICLISTspam_OUTMITVMA.MIT.EDU> >From: Gerhard Fiedler <@spam@listsKILLspamHOME.COM> >Subject: Re: PC Hardware (again) >To: KILLspamPICLISTKILLspamMITVMA.MIT.EDU >In-Reply-To: <RemoveME3.0.1.32.19981229103720.00691ca8TakeThisOuTpop.fast.net> > >At 10:37 12/29/98 -0500, Andy Kunz wrote: >>How do I tell teh UART in a PC to speak even though the modem/handshake >>lines tell it not to? > >can you get more specific? AFAIK, all the handshake lines (RTS, CTS, DTR) >in normal UARTs are software controlled, but i've seen more advanced SCCs >which would allow to configure a hardware controlled handshake. > >ge > Hey guys Talking about the handshake lines in (RTS CTS DTR, do u have to program the pic (example: pic16c73 in this case) to configure these lines, even when you're not going to use it? What I'm saying is that I'll fixing up a null modem for the RS232 cable, using only TX, RX & gnd. Take the example below quoted from a tutorial application from microchip, It says, "We will also use RC5 and RA5 as the terminal handshake lines RTS and CTS, although these signals are not used in this application. Following convention though we will set RTS as an input and CTS will be driven low. " the codes:" ;RTS must be = 00 cts MUST = 00 BSF PORTC,5 ;RTS BSF PORTA,5 ;CTS Dazed & confused? Bye ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com

At 19:01 12/30/98 -0800, chrispian khoo wrote: >Talking about the handshake lines in (RTS CTS DTR, do u have to program >the pic (example: pic16c73 in this case) to configure these lines, even >when you're not going to use it? What I'm saying is that I'll fixing up >a null modem for the RS232 cable, using only TX, RX & gnd. > >Take the example below quoted from a tutorial application from >microchip, > >It says, "We will also use RC5 and RA5 as the terminal handshake lines >RTS and CTS, although these signals are not used in this application. >Following convention though we will set RTS as an input and CTS will be >driven low. " if you're not using these lines, you don't have to use them :-) seriously, some comm apps expect something on the CTS input of the UART, so it's usually a good thing to loop RTS (from PC UART) back to CTS (of PC UART) if that might be the case. other than that you don't have to worry about these handshake lines. ge

Andy Kunz wrote: > How do I tell the UART in a PC to speak even though the modem/ > handshake lines tell it not to? So in summary, on the 8250 series, it is the other way around, your software has to implement any handshake dependencies/ flow control you require. It's all up to you! Some early programs *may* require preconditions, such as valid DCD, to send data (I used to use the Motorola 6850 which had this restriction) but except for a "tied" application, these are now *obsolete*. (It was in the event necessary to link out DCD in the 6850 - a totally useless "feature".) They have been rendered obsolete by the virtually universal adoption of the Hayes Modem standard, which requires that the modem be commanded in order to connect. When it is commanded it is of course, off line and the DCD is necessarily "false". Hayes modems do make certain expectations of the handshake lines, so you do in practice need to provide suitable control of these, but all of these may *if required* be disabled in the modem. Basically, you provide the software support to suit the modem/ application, the UART places no restriction other than those sequence/ timing matters implicit in its buffering. -- Cheers, Paul B.

Hi, the UART in a PC WILL speak always if you want. The question is: how do you tell it to it? - if you write the data register (THRE/TSRE bits should be checked before as they both must be 1), the data will be transmitted regardless of the status of the handshake lines. - if you use the BIOS services (INT 14h) use a loopback connector for handshake lines (RTS-CTS, DSR-DTR-DCD) - if you use something other, (some 3rd party routines) then RTFM. All I wrote here is true using DOS. I hope this helps. Imre On Tue, 29 Dec 1998, Andy Kunz wrote: {Quote hidden}> How do I tell teh UART in a PC to speak even though the modem/handshake > lines tell it not to? > > It looks like THAT is more of a problem than the IRQs were :-( > > Andy > > ================================================================== > Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA > ================================================================== > >