Post by thread:PIC's USART with MAX232, possible?

Great Masters of the PIC, I need of your wisdom again :) I am planning to use a MAX232 to get true RS232 levels on a project I am working in. I intend to use the USART of a PIC16C63 for asynch comm, but according the datasheets of this PIC (I may've missed something) the levels of the TX and RX pins for the USART are true RS232 (i.e. start bit=low level), and the MAX232 inverts the signals. So the question is: can I use the pic's USART with the MAX232????? And if so, how? TIA Calvin

At 08:03 PM 3/3/98 -0600, you wrote: >Great Masters of the PIC, > >I need of your wisdom again :) > >I am planning to use a MAX232 to get true RS232 levels on a project I am >working in. >I intend to use the USART of a PIC16C63 for asynch comm, but according the >datasheets of this PIC (I may've missed something) the levels of the TX and >RX pins for the USART are true RS232 (i.e. start bit=low level), and the >MAX232 inverts the signals. >So the question is: can I use the pic's USART with the MAX232????? >And if so, how? > >TIA > >Calvin > Hi Calvin, Yes, you can use the MAX232 with the PIC USARTs. I have used other members of the MAX2xx family of level converters with 16C65A and 16C74, and it works. You must be getting confused somewhere because the output of the PIC does need to be inverted (by the MAX232). No additional inverters or any other circuits are necessary. Sean +--------------------------------+ | Sean Breheny | | Amateur Radio Callsign: KA3YXM | | Electrical Engineering Student | +--------------------------------+ Fight injustice, please look at http://homepages.enterprise.net/toolan/joanandrews/ Personal page: http://www.people.cornell.edu/pages/shb7 spam_OUTshb7TakeThisOuTcornell.edu Phone(USA): (607) 253-0315

Hi Calvin, You should be able to connect the MAX232 to the PIC as you would ordinarily use it with any NRZ (Non-Return to Zero) Driver. That means the TX output from the PIC (Pin 17) goes to Pin 11 (T1IN) of the MAX232 and Pin 14 (T1OUT) goes to your RS-232 Connector "TX" Pin. The PIC's RX pin (18) is connected to R1OOUT (Pin 12) and the RS-232 Connector's "RX" Pin Goes to Pin 13 (R1IN) of the MAX232. Good luck, myke {Quote hidden}>Great Masters of the PIC, > >I need of your wisdom again :) > >I am planning to use a MAX232 to get true RS232 levels on a project I am >working in. >I intend to use the USART of a PIC16C63 for asynch comm, but according the >datasheets of this PIC (I may've missed something) the levels of the TX and >RX pins for the USART are true RS232 (i.e. start bit=low level), and the >MAX232 inverts the signals. >So the question is: can I use the pic's USART with the MAX232????? >And if so, how? > >TIA > >Calvin > > "If people don't know what you're doing, they don't know what you're doing wrong." - Sir Humphrey Appleby K.C.B

The MAX232E version improves on ESD protection to +- 15 kV -- requires 4 each 1uF caps for the charge pump. Rich At 10:12 PM 3/3/98 -0500, you wrote: {Quote hidden}>At 08:03 PM 3/3/98 -0600, you wrote: >>Great Masters of the PIC, >> >>I need of your wisdom again :) >> >>I am planning to use a MAX232 to get true RS232 levels on a project I am >>working in. >>I intend to use the USART of a PIC16C63 for asynch comm, but according the >>datasheets of this PIC (I may've missed something) the levels of the TX and >>RX pins for the USART are true RS232 (i.e. start bit=low level), and the >>MAX232 inverts the signals. >>So the question is: can I use the pic's USART with the MAX232????? >>And if so, how? >> >>TIA >> >>Calvin >> > >Hi Calvin, > >Yes, you can use the MAX232 with the PIC USARTs. I have used other members >of the MAX2xx family of level converters with 16C65A and 16C74, and it >works. You must be getting confused somewhere because the output of the PIC >does need to be inverted (by the MAX232). No additional inverters or any >other circuits are necessary. > >Sean > > > > >+--------------------------------+ >| Sean Breheny | >| Amateur Radio Callsign: KA3YXM | >| Electrical Engineering Student | >+--------------------------------+ >Fight injustice, please look at >http://homepages.enterprise.net/toolan/joanandrews/ > >Personal page: http://www.people.cornell.edu/pages/shb7 >.....shb7KILLspam@spam@cornell.edu >Phone(USA): (607) 253-0315 > > ========================================= = Abolish the Income Tax! Fire the IRS! = = http://www.nrst.org/ = =========================================

On Tue, Mar 03, 1998 at 08:03:50PM -0600, Calvin wrote: > I am planning to use a MAX232 to get true RS232 levels on a project I am Use a MAX202 - same price, only needs 0.1uF caps instead of electrolytics. > datasheets of this PIC (I may've missed something) the levels of the TX and > RX pins for the USART are true RS232 (i.e. start bit=low level), and the > MAX232 inverts the signals. Correct; the RS232 TD and RD levels ARE inverted, i.e. at RS232 voltage levels, a mark is -ve and a space is +ve. The control lines, OTOH, are true signal levels, therefore if you use port pins for CD etc, then the port level will be inverted. -- Clyde Smith-Stubbs | HI-TECH Software Email: clydeKILLspamhtsoft.com | Phone Fax WWW: http://www.htsoft.com/ | USA: (408) 490 2885 (408) 490 2885 PGP: finger .....clydeKILLspam.....htsoft.com | AUS: +61 7 3354 2411 +61 7 3354 2422 --------------------------------------------------------------------------- ANSI C for the PIC! Now shipping! See http://www.htsoft.com for more info.