libftdi Archives

Subject: Re: First byte of LT245R eeprom

From: Anders Larsen <al@xxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Fri, 01 Feb 2013 11:59:32 +0100
On 2013-02-01 11:04, Uwe Bonnes wrote:
>>>>> "Karl" == Karl Cunningham <karlc@xxxxxxxxxx> writes:
Karl> We have been using an FT245R for several years, programming them Karl> with libftdi v0.16 with an older Ubuntu system. After programming
    Karl> one with libftdi1 v1.0, we can't communicate with it.

Karl> I traced the problem to a difference in what is programmed into Karl> the first byte of the eeprom. v1.0 is programming that byte as Karl> 0x00. Version 0.16 originally did that too, but I had modified it Karl> to program with 0x09 to match what MProg was doing. This made the
    Karl> chip work for us.

I think bit 3 of Eeprom byte 0 is not yet documented in libftdi. If you have access to mprog, experiment a little to find out it's meaning and document
and in lin libftdi.

Bit 3 might be DRIVER_VCP, although libftdi does not touch it for TYPE_R.

When experimenting with an FT245R I found that bit 0 is the culprit - when cleared, an FT245R is turned into an FT232R (or so it seems). If you turn the bit back on, the functionality of the FT245R is restored.

Unfortunately, there is no way (that I know of) to detect if a chip is really an FT232R or an FT245R other than checking bit 0 of byte 0.

Cheers
Anders
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