Some PCs and other equipment will tolerate 0-5v as RS232 comms. A lot more wont and if you need RTS, CTS, DTR, DSR a MAX232 is the way to go.
I made up a utility board driven via my Wisp programmer's supply that's very handy for linking up projects under test to a PC. I've got some schematics and overlays if anyone wants the info. Rich G-G -----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Sebastien Lelong Sent: 21 July 2009 17:49 To: [email protected] Subject: [jallib] Re: jaluino (first schematic... Richard ?) Nice schematic, I can't wait to see the layout. I know PICAXE chips (in fact, Microchip microcontrllers) are connected to serial interface via 3 resistors, no MAX chip between... and everything is just fine. I think this assumes the peripheral on the other side (eg. a PC) understands RS232 level between 0 and 5V, instead of -12V and +12V. It's sometime the case, and to be sure, using a MAX232 chip is better. That said, with the "plug your own serial module" option, you can choose whatever you want. This gives a fourth option, a the cheap side, so we new have: - FTDI chip based USB-to-serial adaptor - 18F14K50 based USB-to-serial adaptor - MAX232 based, with DB9 connector - resistor based, with DB9 connector - (and last option: "my own way to deal with serial") Some more thoughts about the board. Original Arduino Diecimila uses a Atmega168, a 28-pins chip. See: http://arduino.cc/en/Main/ArduinoBoardDiecimila . From this, 20 pins are "exported" through connectors on sides, where 2 pin are dedicated to RX/TX, thus involved in board's functionality (I mean there aren't completely free, as they are involved in serial). Using a 18F4550, there are a lot more pins: 40. From these 40 pins, only 33 can be used: 2 x 2 pins for Vss/Vdd, 1 pin for MCLR, and 2 pin for OSC/Xtal. The board will provide serial (2 pins), USB (3 pins), optionally I²C (2 pin). Even if these pins are already involved in something on the board (a functionality), I think they all should be exported. This will finally give 33 pins which can be exported, plug to side connectors. This is 15 pins more than official Arduino. My question is: how will we be pin-compatible with existing Arduino shields ? My answer would be: Jaluino board won't be compatible, but we can design a shield to it adapts Jaluino to Arduino connectors. Any suggestions, advices, comments, ... ? Also note some Arduino-like big fat boards, with far more than 28-pin chip exist: http://arduino.cc/en/Main/ArduinoBoardMega http://www.liquidware.com/shop/show/ILL/Illuminato Seb -- Sébastien Lelong http://www.sirloon.net http://sirbot.org --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/jallib?hl=en -~----------~----~----~----~------~----~------~--~---
