new to serial communication

sgeorgia

I've read through some of the info. on the serin and serout instructions. However, it is not very clear whether I should use max232(or a similar device)·or not in my project. The fact that there is no 'level shifter' on the stamp or the carrier board confuses me. The manual states there needs to be a some sort of level shift. Does the PC understand TTL? Does the stamp understand RS232? I'm trying to figure out whether I should include a max232 or not.

Martin Hebel

The BASIC Stamp does invert the signals, and as long as you use the programming·IO using DEBUG/DEBUGIN or SERIN 16/SEROUT 16 no additional hardware is needed.· If you use other IO (P0-P15) signal conversion would be needed.· Be aware the programming port echos data back to the sender.

-Martin


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Martin Hebel
StampPlot - Graphical Data Acquisition and Control
AppBee -·2.4GHz Wireless Adapters & transceivers·for the BASIC Stamp & Other controllers·

allanlane5

Martin is correct. The BS2 'programming port' (number 16) does have a couple of level-shift transistors on it. So, if you use the 'standard' progamming port in your program, the level shifting is already taken care of for you.

The BS2 can do SEROUT/SERIN on any I/O pin, but if you use I/O pins zero through 15, then you would need to use a MAX232 to talk to a 'real' RS232 device.

Note there are many BS2 peripherals (LCD displays, etc) which use TTL-based RS232 signalling. For those you would not need the max232 chip.