So I am looking to finally make a custom arduino board with my circuit and ancilliaries on it, and am trying to figure out the best way of putting USB connectivity on it. I am looking at the mega and see that the arduino folks updgraded from a Ft232 to using a 16u2 to give USB chitchat. I always thought the FT232 was expensive hence the move away from it, but the priceing is the same. However hte 16u2 takes a lot more support hdw, so I am wondering what the benfit is to the more complex circuit w/ higher parts count. It seems easier to just throw a ft232 at it rather than deal with uploading code to a complex 16u2.
Both parts are a pain to manually solder. I find it easier to use a module with all components in place:
Has everything but Rx/Tx LEDs.
Includes chip, connector, caps, board, almost a wash vs stocking more parts and adding all those by hand.
But if you need the flexibility that 16U2 offers, being programmable & all ...
A variety of modules are available, including ones as cheap as $2 (albeit not the FT232, but the difference is only in the drivers) which are cheaper than sourcing the chip itself. They can be soldered to a main board - or socketed. They can be fitted over other parts making the design more compact in the process.
The only real advantage of a 16U2/ 32U2 is having HID functionality or tandem processing.
Note that as far as FTDI goes, there are new chips that are significantly cheaper than the ft232rl used on the older arduinos.
The ft230x and 234x are about half the price and come in smaller packages. There's even a $6 module UMFT234XF (though it looks like a nightmare from a cable-stress-relief PoV.)
I still use the FT232Rx, I don't have to program it (and allow for an ISP header) and it "just works". I've been tempted to try the newer smaller versions but it if ain't broke...
I am liking going with the FT232 or equiv as it lets me leave off one more ISP header, and one less thing to worry about, it either just worksout of the box, or will never work. No software to mess up etc. The whole goal here is to condense, so as new daughter board is a bad idea, I want it a permanent part of the pcb, so I just need to sort this out. Pro boards, small quantity, but I will probably be hand soldering them all, maayyyyybbbbeee ghetto reflow, but not at first, so there is deff a minimum package side I can deal with, and no center pads!
I don't think there was - or is - ever a question of using the 16U2/ 32U2 unless you wanted HID (or other fancy USB) functionality or some exotic intermediate processing. It certainly is not a matter of cost.
That said, you have not described the context of your proposed project - few custom units or full production and sale; requirement for on-site or return-to-base (software) upgrade. If ICSP is only required for initial manufacture, you do not fit the pins - or even holes, but use the pads only and a "pogo pin" jig for that first burn. Which also applies to your main processor.
@Crossroads,
Any idea why they put the numbers 232 in the name when the only other thing out there with those numbers is RS232 which is not TTL or USB ?
Long answer: Because it looks like a serial port to the PC application I can only assume they did what most people do, equate "serial" with "RS232", either because they didn't know any better (unlikely) or maybe as a marketing ploy because they knew most people make that connection.
I can't really think that either of those options is likely, after all anyone designing a board with these chips would know the difference and certainly those designing the chip would know.
raschemmel:
Any idea why they put the numbers 232 in the name when the only other thing out there with those numbers is RS232 which is not TTL or USB ?
It is in fact, all of RS-232 bar the levels. So of course, you pair it with a MAX232 (or in fact, MAX237) and you have a (complete) RS232 port. Which is pretty much what a USB to RS232 cable contains.
USB is "the go", newer model ("consumer grade") PCs no longer have serial ports and USB provides a nice little power source to peripherals which RS232 never did except maybe for mice - a bit dodgy for scanners and disk drives, but adequate for many Arduino or similar projects. I have been Hoovering the adapters on eBay, even the five pin ones, don't much care whether FTDI, CP2102 or that other thing; not sure what I am going to do with them all just yet, but I will certainly have the flexibility.
