Post by thread:[PIC]: Reset PIC using Com Port

part 1 203 bytes content-type:text/plain; (decoded 7bit) Hi all currently I am using the circuit in the attach file to reset my PIC by com port. Just to check is this method advisable and is there any better way. regards part 2 15715 bytes content-type:image/jpeg; (decode) part 3 105 bytes -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

Well, I'd place a current limiting resisor on the base of the transistor. Also, did you mean to use the RTS (Request To Send) pin as a reset ? -----Original Message----- From: PSL [.....pslnKILLspam@spam@STARHUB.NET.SG] Sent: 30 June 2002 06:30 To: PICLISTKILLspamMITVMA.MIT.EDU Subject: [PIC]: Reset PIC using Com Port Hi all currently I am using the circuit in the attach file to reset my PIC by com port. Just to check is this method advisable and is there any better way. regards -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

Yes I have use the RTS PIN to reset it RX and TX Pin are used. Will it have any problem in power consumption? Regards ----- Original Message ----- From: "Joe Farr" <EraseMEjoe.farrspam_OUTTakeThisOuTKCSL.UK.COM> To: <PICLISTspam_OUTMITVMA.MIT.EDU> Sent: Sunday, June 30, 2002 1:45 PM Subject: Re: [PIC]: Reset PIC using Com Port Well, I'd place a current limiting resisor on the base of the transistor. Also, did you mean to use the RTS (Request To Send) pin as a reset ? {Original Message removed}

Without a current limiting resistor on the base of the transistor, you stand a good chance of damaging it or perhaps the gate on the MAX232. Try it with a 1K resistor. -----Original Message----- From: PSL [@spam@pslnKILLspamSTARHUB.NET.SG] Sent: 30 June 2002 07:33 To: KILLspamPICLISTKILLspamMITVMA.MIT.EDU Subject: Re: [PIC]: Reset PIC using Com Port Yes I have use the RTS PIN to reset it RX and TX Pin are used. Will it have any problem in power consumption? -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

Thanks for the infor ----- Original Message ----- From: "Joe Farr" <spamBeGonejoe.farrspamBeGoneKCSL.UK.COM> To: <TakeThisOuTPICLISTEraseMEspam_OUTMITVMA.MIT.EDU> Sent: Sunday, June 30, 2002 2:41 PM Subject: Re: [PIC]: Reset PIC using Com Port Without a current limiting resistor on the base of the transistor, you stand a good chance of damaging it or perhaps the gate on the MAX232. Try it with a 1K resistor. -----Original Message----- From: PSL [RemoveMEpslnTakeThisOuTSTARHUB.NET.SG] Sent: 30 June 2002 07:33 To: PICLISTEraseME.....MITVMA.MIT.EDU Subject: Re: [PIC]: Reset PIC using Com Port Yes I have use the RTS PIN to reset it RX and TX Pin are used. Will it have any problem in power consumption? -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestEraseMEEraseMEmitvma.mit.edu

> Just to check is this method advisable and is there any better way. - T + R (one transistor less, one resistor more): http://www.voti.nl/wloader Wouter van Ooijen -- Van Ooijen Technische Informatica: http://www.voti.nl Jal compiler, Wisp programmer, WLoader bootloader, PICs kopen -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu

Actually, a proper RS232 driver has a guaranteed minimum source impedence, which would eliminate the need for the resistor. However, the resistor is _very_ cheap insurance. Bob Ammerman RAm Systems ----- Original Message ----- From: "PSL" <RemoveMEpslnTakeThisOuTspamSTARHUB.NET.SG> To: <EraseMEPICLISTspamspamBeGoneMITVMA.MIT.EDU> Sent: Sunday, June 30, 2002 2:46 AM Subject: Re: [PIC]: Reset PIC using Com Port > Thanks for the infor > ----- Original Message ----- > From: "Joe Farr" <RemoveMEjoe.farrKILLspamKCSL.UK.COM> > To: <PICLISTSTOPspamspam_OUTMITVMA.MIT.EDU> > Sent: Sunday, June 30, 2002 2:41 PM > Subject: Re: [PIC]: Reset PIC using Com Port > > > Without a current limiting resistor on the base of the transistor, you stand > a good chance of damaging it or perhaps the gate on the MAX232. Try it with > a 1K resistor. > > > {Original Message removed}

> currently I am using the circuit in the attach file to reset my PIC by com > port. > Just to check is this method advisable and is there any better way. I don't like the MAX232 connected to the base of the transistor directly. There should be a base resistor to limit the base current. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestSTOPspamEraseMEmitvma.mit.edu

>> Without a current limiting resistor on the base of the transistor, you stand a good chance of damaging it or perhaps the gate on the MAX232. Try it with a 1K resistor. << I like a 10Kohm resistor better. There is no need to draw nearly 5mA just to turn on the transistor. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestspamBeGonemitvma.mit.edu

> Actually, a proper RS232 driver has a guaranteed minimum source impedence, > which would eliminate the need for the resistor. However, the resistor is > _very_ cheap insurance. Are you sure this is true for the 5V side where he hooked it up? It sounds a little odd, but I don't have the spec sheet in front of me right now. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestEraseMEmitvma.mit.edu

> Actually, a proper RS232 driver has a guaranteed minimum source impedence, > which would eliminate the need for the resistor. However, the resistor is > _very_ cheap insurance. But that referes to the RS232 side, and the transistor is on the other side! But (re my earlier response) why use a transistor at all? Wouter van Ooijen -- Van Ooijen Technische Informatica: http://www.voti.nl Jal compiler, Wisp programmer, WLoader bootloader, PICs kopen -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-request@spam@spam_OUTmitvma.mit.edu

Looks good (except for the base resistor mentioned several times already). May I offer the following simplification though: use a diode in place of the transistor, anode to MCLR, cathode to MAX232 output. The reason you are using a transistor in the first place is simply to achieve a logic "OR" of the two possible reset signals. Pin 7 (RTS) is a good choice I think. (RTS = Reset The Sucker?). I am using the same pin because I run Shane Tolmies bootloader in conjunction with Petr Kolomazniks downloader, both from: www.workingtex.com/htpic/PIC_bootloader.htm The downloader program generates a reset signal on RTS, which means you don't have to manually reset or power down the micro to initiate the bootloader. > Hi all > > currently I am using the circuit in the attach file to reset my PIC by > com port. Just to check is this method advisable and is there any > better way. > > regards > > -- Brent Brown, Electronic Design Solutions 16 English Street, Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/txt: 025 334 069 eMail: spamBeGonebrent.brownKILLspamclear.net.nz -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestspam_OUTmitvma.mit.edu

> But (re my earlier response) why use a transistor at all? So it's OK to short MCLR to ground with a pushbutton switch that was also shown on the schematic. The transistor is required unless the MAX232 5V-side output is open collector, which I didn't think it was. I don't have the spec sheet in front of me right now. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-request.....TakeThisOuTmitvma.mit.edu

> > But (re my earlier response) why use a transistor at all? > > So it's OK to short MCLR to ground with a pushbutton switch that > was also shown on the schematic It's recommended to have a series resistor (220R) into MCLR, and if using a reset switch to ground MCLR through 100R. Also a cap (eg 10n) from MCLR to ground to ensure that MCLR reaches Vcc after the Vcc pin does ( if POR function is not used - DS00007 ) -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestKILLspamspammitvma.mit.edu

> > But (re my earlier response) why use a transistor at all? > > So it's OK to short MCLR to ground with a pushbutton switch that was also > shown on the schematic. The transistor is required unless the MAX232 > 5V-side output is open collector, which I didn't think it was. I don't have > the spec sheet in front of me right now. (as used http://www.voti.nl/wloader ) Shorting MCLR with a switch is possible with a resistor from the MAX to the PIC. An extra resistor between the MAX and the Vcc is advised to guarantee a MCLR Voltage that is high enough. Wouter van Ooijen -- Van Ooijen Technische Informatica: http://www.voti.nl Jal compiler, Wisp programmer, WLoader bootloader, PICs kopen -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> > Actually, a proper RS232 driver has a guaranteed minimum source impedence, > > which would eliminate the need for the resistor. However, the resistor is > > _very_ cheap insurance. > > Bob Ammerman > > Are you sure this is true for the 5V side where he hooked it up? It sounds > a little odd, but I don't have the spec sheet in front of me right now. >Olin Well, I am not 100% sure, but I'd say a good 99 44/100%. If nothing else so that the signal can be considered power-limited in the electrical code sense. (Hm... 12V at big amps and a short-circuit can make a nice fire). Bob Ammerman RAm Systems -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics