Introduction: FTDI Cable
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About: Maker of all trades ... or at least many :) Interested in electronics including programming, woodworking, how to grow edible plants in cold climate of my homeland, building clever dwelling houses from mostly t…
The FTDI chip only comes in very small SMD package (SSOP28) so a word of caution that etching a board for it at home is not easy. I had a chance to use nicely equipped school lab and made this on two sided photoresist copper board. I have never tried laser printer and iron method for transferring the image so I don't know if it is reliable to make so tiny traces with that method. I have a suggestion that it is possible to etch a one sided board and build the bottom layer from wires, see further below.
Anyway, in case someone finds this documentation helpful, here it is. Eagle files are below.
The Eagle files are made with Eagle 5.7.
There are repairs for my mistakes visible on the photos. One schematic mistake I made is fixed in the published Eagle files.
FT232RL datasheet here. Don't get confused about the chapters regarding programming the chip, it comes with defaults that allow for this use perfectly.
The bottom side is simple enough that it can be fixed if it does not align properly or something else goes wrong. In my case that side got over etched and I duplicated all traces with a strand from stranded wire.
Therefore I think that you might be able to use one sided board if you place header pins another way and freeform the bottom side from wire instead.
For soldering the FT232 chip which has only 0.65mm pitch legs I used following method. First I cleaned the pads with rosin, then covered with solder, then removed the solder with solder wick. This still left the traces covered in very thin layer of solder. Then I aligned the chip with the pads and heated each leg for a short time with soldering iron. And it worked.
Vias are made drilling with 0.7mm drill bit and using a single strand from stranded wire. And as you can see on the images the wire strands can be used for fixing mistakes also if they happen, you just have to find some clever way to keep it steady until you finish soldering it in place.
Parts list:
* 0603, 0805 and 1206 mark the physical size of SMD components (in growing order). It is possible to solder SMD components that are "one or two sizes smaller" to another size pads. Somewhat more difficult with a bigger than meant package. Eyeball the image of the board layout with this info in mind if your supply of components does not match exactly.
Anyway, in case someone finds this documentation helpful, here it is. Eagle files are below.
The Eagle files are made with Eagle 5.7.
There are repairs for my mistakes visible on the photos. One schematic mistake I made is fixed in the published Eagle files.
FT232RL datasheet here. Don't get confused about the chapters regarding programming the chip, it comes with defaults that allow for this use perfectly.
The bottom side is simple enough that it can be fixed if it does not align properly or something else goes wrong. In my case that side got over etched and I duplicated all traces with a strand from stranded wire.
Therefore I think that you might be able to use one sided board if you place header pins another way and freeform the bottom side from wire instead.
For soldering the FT232 chip which has only 0.65mm pitch legs I used following method. First I cleaned the pads with rosin, then covered with solder, then removed the solder with solder wick. This still left the traces covered in very thin layer of solder. Then I aligned the chip with the pads and heated each leg for a short time with soldering iron. And it worked.
Vias are made drilling with 0.7mm drill bit and using a single strand from stranded wire. And as you can see on the images the wire strands can be used for fixing mistakes also if they happen, you just have to find some clever way to keep it steady until you finish soldering it in place.
Parts list:
- FT232RL chip (SSOP28 package)
- 2 x 100nF SMD capacitors 0805 package*
- 1 x 10 nF SMD capacitor 0603 package*
- 2 x LED SMD 1206 package*
- 2 x ~270 ohm SMD resistors 0603 package*
- 1 x ferrite SMD 0603 - I didn't have good source for ordering those in small amount, but I found that a dead scanner control board had like 5 of them. They were black, without markings and thicker than resistors, but mostly it is the specific ferrite color that helps to find them.
- 1 x 10uF capacitor electrolytic
- female pin headers 6x1 angled
- male pin headers 3x1
- a jumper. Can be found on old motherboards and HDDs. Along with the male headers it allows to use this cable easily on both 3.3V and 5V controller boards. So it's optional, you can solder a wire there instead if you only have one type of boards on your mind.
- USB cable. From any broken USB device.
* 0603, 0805 and 1206 mark the physical size of SMD components (in growing order). It is possible to solder SMD components that are "one or two sizes smaller" to another size pads. Somewhat more difficult with a bigger than meant package. Eyeball the image of the board layout with this info in mind if your supply of components does not match exactly.
