Hello Gerd, I could not connect the signal directly to the FT4232H DI pin as I think the pin has a pull-up resistor and this is distorting my signal. Hence, I put in a d-flip flop in-between. Please let me know if you have any ideas/suggestions..
Thanks Siva From: [email protected] To: [email protected] Subject: RE: MPSSE baudrate Date: Mon, 4 Jan 2010 10:14:22 -0500 Hello Gerd, I am sorry for giving the impression that FT4232H is an SPI slave. I am using it as an SPI master. I just want to sample a 1.5 MHz signal at either 3Mhz, 6MHz or 12 MHz. This is the configuration I have: FT4232H -> Clock signal -> Flip flop clock FT4232H <- DI signal <- Flip flop Data output Flip flop Data Input <- 1.5 MHz signal FT4232H -> DO signal -> 1Meg resistor -> GND FT4232H -> CS signal -> 1Meg resistor -> GND Can I assume that if I set the baudrate to 0.75 MHz, I will be sampling the signal at 3 MHz in MPSSE SPI mode? I read about async bitbang mode but I surmised that it cannot work at those speeds? Can you please confirm from your experiences? Any thoughts, please? Thanks Siva > From: [email protected] > To: [email protected] > Subject: Re: MPSSE baudrate > Date: Mon, 4 Jan 2010 11:15:19 +0100 > CC: [email protected] > > Hi Siva, > > > I am a beginner to using FTDI chips and want to use FT4232H for sampling a > > 1.5 MHz line. I am hoping that if I could run MPSSE SPI at a baud rate of > > > 3Mhz or 6 Mhz, will give me a reliable sample. > > Do you want to read data from an SPI communication or do you want to sample > the data at a defined frequency without the FT4232H "understanding" the SPI - > like a logic analyzer? > > When you want the FT4232H to act as SPI slave and read data, the best way is > to use the MPSSE. I haven't done this myself and currently we lack a good > example in libftdi for that. But there is code out there which does it. > > When you plan to use the FT4232H like a logic analyzer and sample the data at > a defined baudrate, then the bitbang mode is what you want. > > You need to enable the bitbang (e.g. async bitbang), set the baudrate you > want > and start to read continously. > > Currently there is some uncertainty about how the bitbang baudrates really > work. The datasheet says you need to set 1/16 the baudrate you want for > bitbang - but we observed that it just gives you 1/4 of the speed you wanted. > So the code currently multiplies the speed by 4. > > Kind regards, > > Gerd > > -- > libftdi - see http://www.intra2net.com/en/developer/libftdi for details. > To unsubscribe send a mail to [email protected] > Hotmail: Trusted email with powerful SPAM protection. Sign up now. libftdi - see http://www.intra2net.com/en/developer/libftdi for details. To unsubscribe send a mail to [email protected] _________________________________________________________________ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ -- libftdi - see http://www.intra2net.com/en/developer/libftdi for details. To unsubscribe send a mail to [email protected]
