I'm looking at connecting my 18F4520 to the PC via the serial port and I gather from another thread that an interface chip such as the Max232 is required. I wonder though why that is necessary as the PicAxe project boards communicate with the PC via the Pic's serial port with only a direct connection to the Pic Tx pin and a resistor divider to the Rx pin (or maybe it's the other way around). I suppose I could try it that way but would like to ask for some advice b/f risking damage to the chip or PC port
Any assistance appreciated......
Laurie Forbes
Why Use a Max232?
Moderators: David Barker, Jerry Messina
TTL levels are 5v logic 1 and 0v logic 0 and are inverted when compared to RS232 levels of +12v and -12v.
While most modern serial ports will accept 0-5 volts and you can invert in software it is not standard and is unadvisable.
If you plug onto an older serial port your gonna get a poped pic.
the picaxe just inversts the logic in software which you can 'get away with' personally i'd never do it.
if your wanting to use the hardware uart on a pic then you must use a max232 as logic levels are fixed in hardware , only software serial is capable of this type of jiggery pokery.
While most modern serial ports will accept 0-5 volts and you can invert in software it is not standard and is unadvisable.
If you plug onto an older serial port your gonna get a poped pic.
the picaxe just inversts the logic in software which you can 'get away with' personally i'd never do it.
if your wanting to use the hardware uart on a pic then you must use a max232 as logic levels are fixed in hardware , only software serial is capable of this type of jiggery pokery.
If you can read this you are too close
Ah, thanks for the explanation. Looking again at the Picaxe schematic, I see that the serial in line has the resistor divider, I guess to reduce the RS232 level to 5V or so, while the serial out can be connected directly.
I think I'm gonna try it anyhow (don't have a max232 handy and it might be educational in any case).
Thanx again for the help.......
Laurie Forbes
Update:
Switched program to software UART and transmit to PC works perfectly. Now to try transmitting to Pic....
I think I'm gonna try it anyhow (don't have a max232 handy and it might be educational in any case).
Thanx again for the help.......
Laurie Forbes
Update:
Switched program to software UART and transmit to PC works perfectly. Now to try transmitting to Pic....