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krzysztofgawrys / libmpsse

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FT232H does not use open-drain outputs #27

Closed GoogleCodeExporter closed 8 years ago

GoogleCodeExporter commented 8 years ago 
The FT232H supports open-drain outputs to become fully I2C compatible. This 
prevents bus conflicts when a slave device tries to acknowledge.

Original issue reported on code.google.com by p.voorth...@gmail.com on 26 Apr 2013 at 4:03

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GoogleCodeExporter commented 8 years ago 
The existing Tristate function should enable the FT232H's open-drain outputs 
(http://code.google.com/p/libmpsse/source/browse/trunk/src/mpsse.c#1239). Is 
this what you are looking for, or did it not work for you?

Original comment by heffne...@gmail.com on 26 Apr 2013 at 7:59

GoogleCodeExporter commented 8 years ago 
Ah, sorry. I'm working with a older version that did not have the tristate 
function, it does the same.

I have an i2c bus with a 5v i2c device and pull-ups to 5v. This option must be 
enabled otherwise I see the ft232h driving 3v3 during communication. Also the 
slave device cannot pull-down sda to acknowledge an incoming byte.

After seeing page 26 of AN108 I enabled this for the clk and sda lines at 
initialisation.

Original comment by p.voorth...@gmail.com on 27 Apr 2013 at 8:46

GoogleCodeExporter commented 8 years ago 
Yes, after reading page 26 of AN108 I added this to libmpsse. :)  Too bad this 
feature seems to have not occurred to FTDI when making earlier chips.

Original comment by heffne...@gmail.com on 28 Apr 2013 at 1:45

GoogleCodeExporter commented 8 years ago 
is there a way to get tri-state for UART so you can use lower voltage levels 
than 3.3? I read it goes tri-state to an internal resistor, but is there 
another way? Vio seems to not be tolerant of much less than 3.0 volts :( 

I might just have to wait for my Bus Pirate to come later this week.

Original comment by nmz...@gmail.com on 26 May 2013 at 11:47