Hi,
As I continued to search for an answer I finally managed to use this
CBUS thing using libftdi.
The fact is that's not simple for someone who never heard about serial
our USB developpement. So here is what I learned, in case of someone as
newbie as me have the same problems.
The point was simply that I missunderstood "input" and "output" pin
types. To set pins levels from the computer I had to use output pins. I
used input ones... I know this is a basic serial thing, but serial
developpement and electronics are not part of my knowledge. Here data
goes from the computer to the chip, so it's an output from the
computer. I viewed the thing from a chip point of view and then thaught
it had to be an input on the chip. My basic serial knowledge is now
fixed :)
I Also, I thaught I had to set the 3rd bit. It was the bit 3, so the
4th as it begins at bit zero (pin 12 on MM232R module which is
connected to pin 11 on FT232R chip).
My bit mask undestanding was ok, but with all the missunderstanding
rount it, I thaught I was wrong on masks too.
For real newbies like me, also note that bytes bit zero is the far
right one...
So in this cbus setting byte, positions are as the following : 76543210
position 0 : cbus pin 0 level (0 = low, 1=high)
position 1 : cbus pin 1 level
position 2 : cbus pin 2 level
position 3 : cbus pin 3 level
position 4 : cbus pin 4 type (0 = input, 1=output)
position 5 : cbus pin 5 type
position 6 : cbus pin 6 type
position 7 : cbus pin 7 type
So to fix my exemple, here are the right bytes to light my LED on or
off :
ftdi_set_bitmode(&ftdic, 0x87, BITMODE_CBUS); // 0x87 is
10000111 byte to switch on. Cbus pin 3 is output set to low. All other
pins are input and set to high.
ftdi_set_bitmode(&ftdic, 0x8F, BITMODE_CBUS); // 0x8F is
10001111 byte to switch off. Cbus pin 3 is output set to high. All
other pins are input and set to high.
Chears,
Nicolas.
Le 20.03.2009 01:06, Nicolas a écrit :
Hi,
Im really new to this sort of usb device developpement and C code
(started yesterday), so my question is probably very low level. Sorry.
I built a small usb prototype based on MM232R
module that lights a LED when PWREN# (12) pin goes low. It well works
when the EEPROM is configured to have this pin switched on PWREN# event.
After that I configured the EEPROM to accept bitbang on this pin (the
3rd of the 4 bits capables to be used as general purpose I/O) in order
to light my LED using a small C program based on libftdi.
So, I tried to use the ftdi_set_bitmode function, but I can't figure
how to set the bitmask.
I would like to change level of the 3rd bit, but I'm messed up with
bitmasks...
Sometimes it works, I tried all the bitmasks values from 0x00 to 0xFF
and notices that some works. My LED lights sometimes.
Also I don't really know if I should use the bit as input or output.
To illustrate my problem, I can't understand why the bitmask value 0xA6
lights my LED :
ftdi_set_bitmode(&ftdic, 0xA6, BITMODE_CBUS); // 0xA6 is
10100110 bits
and why 0x9A shut it down.
ftdi_set_bitmode(&ftdic, 0x9A, BITMODE_CBUS); // 0x9A is
10011010 bits
What bitmasks should I use to change 3rd pin from low to high and high
to low ? input or output ?
I now it's probably more a question of bitmask understanding than a
libftdi problem, but any help or documentation URLs would be
appreciated to understand this part and begin to learn using this
library.
Thanks,
Nicolas.
libftdi - see http://www.intra2net.com/en/developer/libftdi
for details.
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