Post by thread:[PIC] two hardware serial outputs on PIC18F452?

Hello, maybe this is a dumb question, but... There's a way I can use the MSSP as a second serial (RS485) port? I know I can make it in software but there's need for speed. I was looking in the datasheet and in SPI mode I don't have the 9th bit to emulate a start-bit. I2C also seens of no use here but I can be losing something. Another way would be to use one (or maybe two) parallel to serial shift-registers, use one 8 pins PORT for sending bytes to it, one pin for latching and one PWM output to clock it. Have anyone tried this? That way I think I could have four or more outputs. Just FYI, the outputs are DMX outputs so I need to be able to generate break and mark-after-break. Thank you very much, Brusque -- --------------------------------------------------------------------- Edson Brusque C.I.Tronics Lighting Designers Ltda Research and Development Joinville - SC - Brazil http://www.ryan.com.br/netiqueta.htm http://www.citronics.com.br ---------------------------------------------------------------------

{Quote hidden}>-----Original Message----- >From: spam_OUTpiclist-bouncesTakeThisOuTmit.edu [.....piclist-bouncesKILLspam@spam@mit.edu] >Sent: 04 September 2005 23:45 >To: Microcontroller discussion list - Public. >Subject: [PIC] two hardware serial outputs on PIC18F452? > > >Hello, > > maybe this is a dumb question, but... > > There's a way I can use the MSSP as a second serial >(RS485) port? I >know I can make it in software but there's need for speed. > > I was looking in the datasheet and in SPI mode I don't >have the 9th >bit to emulate a start-bit. I2C also seens of no use here but I can be >losing something. > > Another way would be to use one (or maybe two) parallel to serial >shift-registers, use one 8 pins PORT for sending bytes to it, one pin >for latching and one PWM output to clock it. Have anyone tried this? >That way I think I could have four or more outputs. > > Just FYI, the outputs are DMX outputs so I need to be able to >generate break and mark-after-break. > > Thank you very much, Consider using the MAX3140. This is an SPI controlled UART which also has RS485 drivers on board. If you want to use a separate driver, the MAX3100 just has the UART. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. =======================================================================

Hello Michael, > Consider using the MAX3140. This is an SPI controlled UART which also has RS485 drivers on board. If you want to use a separate driver, the MAX3100 just has the UART. good sugestion but (there's always a but) I need isolated outputs. This reduces the option to the MAX3100 but at US$5.28 (for 25 units at Digikey) they're costly. A pair of shift-registers to each output would be cheaper (if it works). Hey Harold (Hallikainen)! Have you already done a multiple DMX outputs device? Best regards, Brusque

On Mon, 05 Sep 2005 07:07:46 -0300, you wrote: >Hello Michael, > >> Consider using the MAX3140. This is an SPI controlled UART which also has RS485 drivers on board. If you want to use a separate driver, the MAX3100 just has the UART. > > good sugestion but (there's always a but) I need isolated outputs. >This reduces the option to the MAX3100 but at US$5.28 (for 25 units at >Digikey) they're costly. > > A pair of shift-registers to each output would be cheaper (if it >works). > > Hey Harold (Hallikainen)! Have you already done a multiple DMX >outputs device? > > Best regards, > > Brusque An external small PIC will probably be cheaper and more flexible than the Maxim chips. If you design the protocol from the main PIC right you can probably use a bit-bashed UART on the slave PIC to allow use of a cheaper device.