SX Specific RS232 Serial IO

Try the RS232 ISR Timing Calculator to find the clock, prescale, RTCC increment and ISR divider

NEW! Check this out! The RCL-1 RS232 Level Converter in a DB9 backshell

NEW! Why re-invent the wheel? The RS-232 / I²C-Adapter & Parallel I/O Module is already available.

Simple: (no interrupts)

• 9600 baud tx or rx with a 4Mhz crystal and no interrupts in PIC compatibility mode from Lea
• 115.2k baud tx with a 4.096Mhz crystal in PIC compatibility mode from Mike Harrison
• 500k bps tx with a 4Mhz crystal in PIC compatibility mode from Regulus Berdin
• 9600 rx baud Serial In. Dipl.-Ing. Detlef Rohde has ported a program which found in Scott Edwards booklet of Assembler routines for the PIC to the SX28. All what you have to do is to adjust carefully the delay settings for your baud rate. He used the 50 MHz resonator and checked the usage for 9600 baud..

Virtual Peripherals:

• UART_VP: 2400-230.4K UART This is a simplified software module that communicates over an RS-232 port to a PC and will echo back what is received. This is compatible with the SX Demo Board.
  Application note AN38 PDF or CCS HTML
   
• DUART_0412 Dual Universal Full Duplex UARTs for 110 to 115200 baud with Buffering, Handshake and Auto Baud-rate Detect
• DUART_0412_JB (uses stdinc.src) As above but faster, smaller, more configurable and supports the SX52. Thanks to Jim Brain [brain at jbrain,com] who modified the code to
  • make autobaud detection conditional code
  • add high speed configurable UART2 back in
  • clean up code for prod SX52 support
  • add conditional code to inline uart vp code,  (saves 7 cycles per uart)
  • move autobaud code to subroutines, to save space.
     
• Dual UART Dual UART in software for baud rates of 1200,2400, 4800,9600,19200,57600 bps This is compatible with the SX Demo Board.
  Application note AN39 PDF or CCS HTML
   
• Eight UARTs: Eight 19.2k baud UARTs. This software configures the Port B pins as inputs and Port C pins as outputs for the respective UARTs (i.e., UART0=RB.0+RC.0, UART1=RB.1+RC.1, ...). This code is not compatible with the SX Demo Board provided by Parallax, but offers an impressive example of the power of virtual peripherals.
  Application note AN40 PDF or CCS HTML
   
• UART with Parity can be configured at runtime for: TX/RX with or without xon/xoff handshake, TX only with CTS handshake, RX only with RTS handshake. Four selectable baudrates (default 1200,2400,9600,19200) and 7 or 8 databits with parity odd, even or none. Also includes code for a bi-directional 2-wire interface (halfduplex serial line + write enable line used for direction synchronization). By Peter Verkaik.

Integrations:

• 8VP: 19.2kbaud UART, two 8-bit A/D converters, two PWM outputs, one I2C serial link for EEPROMs, two 16-bit independent timers, Time clock (keeps count in msec), a software execution path switcher and push button detection and debounce. SX Demo Enhanced 2.0 by Craig Webb of Parallax Inc.
   
• SXDemo: 19.2k baud UART, two 8-bit A/D converters, two PWM outputs, one I2C serial link for EEPROMs, two 16-bit independent timers, and all implemented as Virtual Peripherals, in software. This is compatible with the SX Demo Board from Parallax, and is the same code is shipped with the Parallax tools.
   
• PowerVP: 19.2k baud 6 port UARTs along with four PWM outputs, four 16 bit timers, and two 8 bit A/D converters. This is not compatible with the SX Demo Board from Parallax, but is a very impressive demonstration of the type of power that software can provide on the right kind of silicon.
   

Also:

• RS-232 / I²C-Adapter & Parallel I/O Module
• SX Microcontroler based "Virtual" Modems
• SX Virtual Peripherals
• Ubicom Virtual Peripheral Library - Interface section
• General RS232@,
• SX Specific RS-485
• TTL to/from RS232@,
• TI Calc@

Calculating Parity

See also:

• http://www.certi.ufsc.br/~cae/irv01.c
• http://www.microchip.com/10/Faqs/tSupport/PICmicro/USART/index.htm
• http://redrival.com/mcgahee/  or http://mcgahee.freeservers.com PICUART.ZIP contains a heavily commented assembly language program/document in MPLAB format that details how to use the PIC16C74's built-in UART
• http://www.scenix.com/virtual/download/Vpg_UART_1_04.src 2400-230.4K UART - This is a simplified software module that communicates over an RS-232 port to a PC and will echo back what is received. This is compatible with the SX Demo Board.(cached 20001010)
• http://www.brouhaha.com/~eric/scenix/fduart/ Eric Smith's Full duplex, 115.2Kbps software UART Virtual Peripheral.
  Permission is granted to use this code or portions thereof for non-commercial purposes provided the copyright notice is preserved intact and credit is given to the author. For any other use, a license may be obtained from the author; send email to eric at TakeThisOuTbrouhaha.com. (cached 19981106)

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Books:

• Serial Port Complete by Janet Louise Axelson, Jan Axelson Lakeview Research

Questions:

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