Uber-easy DIY USB ALDL Cable

[GaryDoug]

The FT232RL will only work if the TXD and RXD pins are inverted, since standard RS232 is already inverted from TTL. Fortunately FTDI included that fix in their programming utility. It's a no-brainer to download the free "FT_Prog" utility and set the TXD and RXD pins to "Inverted" status. http://www.ftdichip.com/Support/Utilities.htm#FT_Prog
That brings the polarity back in sync with the TTL versions. You can't directly tie the two pins together however. See this link for the wiring: http://www.firebirdnation.com/forums/topic/457761-make-an-obd1-cable-for-under-20/page__pid__866681#entry866681

[RobertISaar]

i've built probably 30 cables without ever needing to do so? the first half used a FT232R and another converter IC to change TTL to RS232 to USB. this was before i knew better and just found TTL to USB via a FT232R.

[GaryDoug]

The "another converter" flipped the polarity. Most involve the use of an RS232 IC or a couple of NPN transistors. The TTL-to-USB does not invert the signals to make it RS232 compatible. When I placed the FT232RL alone into use, both signals were upside down, giving complimentary data. Reprogramming fixed that. You may have used a special driver that took care of the inversion already. I have noticed that some companies supply the adapters with their own driver and their adapters will NOT work with the standard drivers from FTDI without the inversion.

[RobertISaar]

i've always used and advocated using the standard drivers from ftdichip.com with no issue. it's possible that the boards i was buying were already running the modified program to account for this.

[GaryDoug]

If you ever want to give that utility a try, the changes will not take effect until the unit is unplugged from the pc and plugged in again (rebooted). It seems that the internal hardware gets set at power-up time and not at program time.

[Achilles]

Will this one work. http://www.superdroidrobots.com/shop...px?itemid=1173

[phonedawgz]

Yes it should

[RobertISaar]

looks like it uses the FT232BL, which is essentially an older version of the FT232RL. other than the circuit on the PCB required to use it being more complex, i don't see any reason why it wouldn't work.

The FT232R is the latest device to be added to FTDI’s range of USB UART interface
Integrated Circuit Devices. The FT232R is a USB to serial UART interface with
optional clock generator output, and the new FTDIChip-ID™ security dongle
feature. In addition, asynchronous and synchronous bit bang interface modes are
available. USB to serial designs using the FT232R have been further simplified
by fully integrating the external EEPROM, clock circuit and USB resistors onto
the device.
The FT232R adds two new functions compared with its predecessors, effectively
making it a "3-in-1" chip for some application areas. The internally generated
clock (6MHz, 12MHz, 24MHz, and 48MHz) can be brought out of the device and used
to drive a microcontroller or external logic. A unique number (the FTDIChip-ID™)
is burnt into the device during manufacture and is readable over USB, thus
forming the basis of a security dongle which can be used to protect customer
application software from being copied.

the features added into the R version aren't really going to effect the end-user of an ALDL cable.

[sherlock9c1]

Can one of you doublecheck my settings? I just completed a benchtop programming setup for '94-95 LT1s and I want to make sure I have all of the driver settings correct. I've done a successful datalog and two successful reads and the files appear identical. Before I try to write, can you verify the settings below are correct:
Bits per second: 9600 (8192 is not a selectable option).
Data bits: 8
Parity: None
Stop bits: 1
Flow Control: None

[RobertISaar]

if you're having good reads(datastream or BINs), then writes should be just fine as well. those look like the default values, which are correct for this application.

[sherlock9c1]

Thank you Robert - I had success with multiple writes and reads. No more risk! I appreciate all of the work that went into this!

[roby]

What is the best way to mount the board in a project box and which cable restraints are most rugged?

[RobertISaar]

i friction-fit everything. the ALDL end, a 13/64 drill in the right place will clamp it in place nicely without risking the integrity of any of the wires. on the USB side... well, that will depend on the exact cable you're using and how you want it to be. i notch it out using a dremel.

i really need to get a small CNC setup, would cut down assembly time to ~20 minutes.

[GaryDoug]

I use this one, case included. Construction time: about 5 minutes total for 12-pin, about 15 minutes total for 16-pin version.
http://www.ebay.com/itm/6pin-FTDI-FT...item5d3713fcc0

[roby]

So does the board just float inside the box on the cables? The female usb socket is flush to the edge of the board, how do you stabilize or secure it to the box to allow cable install and removal?