> HI Ya All,
>Im new to pic programming and would like to know in lame terms
>what is 'bit banging'?

>Phil Adams

Some micros have a UART for serial (ie standard frequency) comms
built into them. Put data into the Transmit register and the micro will
automatically take care of sending the bits out and the timing involved
so that the receiving device can pick it up properly. When the byte has
been transmitted, the micro lets you know. Same thing when data
comes from a remote machine like a PC - the UART picks up data
coming in, fills a Receive buffer and lets you know when the whole
byte is ready to be read. You don't have get your hands dirty with any
data bits, just look for flags or process interrupts

Bit-banging is what you have to do on a micro with no UART. Write
your own routine to send/receive bits out on PIC pins with the
correct timing (say 9600 bits/second) and provision to read Idle
states, as well as Start and Stop bits.

The other type of bit banging is where two devices, say two PICs, can
communicate over a two-wire connection. One wire is Clock, the other
is Data. PIC1 (o/p) sets the Clock line high and puts data on the Data
line. PIC2 (i/p) knows to pick up the data bit when it sees the Clock line
go high. PIC1 puts the clock line low, then high again with a new bit of
data. By alternating the two PICs as master/slave they can swap data
Some micros have SPI or MISO (Master In/Slave Out) pins for talking
to peripherals

Connecting two PIC o/p pins to two status pins on a PC printer port
would let you download data from a PIC+SRAM datalogger without
needing to set up serial comms. Again use Clock/Data and interrogate
the Status Register of the PC to see Clock/Data line changes. On a
modern PC this is a pretty fast transfer method, even in BASIC. You
aren't fixed to any particular frequency, send the data as slowly as you
pick it out of the SRAM and process it and/or as fast as the PC can
reliably receive/store it

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST