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blog:ftdi_usb_-_serial_and_zok_testing

FTDI USB<->serial and Zok testing

The Zok board is a simple test board for atmega644 (and similar atmel avr form factor) chips; good for small projects or as a breakout board, it can be minimally populated (just the avr chip and a couple capacitors) to work, or can have optional buttons, LEDs, crystal, etc put on. It has a toggle button, can take power in and out via header pins, and has space for an FTDI FT232RL chip .. which can allow a host PC/brick to supply power and/or serial over USB.

I hadn't actually tested the USB side of that pcb yet (didn't need it!), as the board was mostly being used for hacking around with robot cars and so forth.

(FWIW, if anyone wants a Zok, let me know, I can sell you a pcb and a few passives to go with it.)

But, I'm back on the Zikzak trail and waffling between making a full rev 4 pcb (with all the jacks, an audio amp, and more) on the main PCB (essentially a full pcb rework) or just make a shield that plops onto the existing rev3 pcb. A shield being just another pcb, that you use extra long headers on and just sandwich it onto the other pcb, offering the peripheral jacks and audio amp and so forth on _that_, without changing the host pcb. Much easier routing job, maybe much cheaper to do…

The core exercise for both options though, is to get the CAD objects put together; as I've ranted about before, CAD libraries are nightmarish things and everyone has to eventually just draft their own parts (schematic symbol, and the physical representation for pcb, and the mapping between.) Making both of those sides to each object is a lot of work.. the schematic is easier, as it needn't be precisely laid out, but requires you to have the correct datasheet or reverse engineering going on. The physical representation requires very precise measuring, so you can define where solder pads will be needed, where to drill holes, etc, and it has to be perfect. I find this part creation for libraries to be a huge de-motivator. Still..

.. so now I've gone and put together parts for all the extra peripherals the ZZ r4 or r3-shield needed; a POT wheel for volume control on the amp; joystick jack; VGA jack; barrel power jack; headphone jack; USB jacks; PS/2 keyboard jack; SD slot; etc and so on. I've got about 20 or so of each part in baggies, so can actually make a few boards as well.

Before committing to a shield design, it'd be wise to test out a few things; the amp circuit has already been tested. The FTDI USB for power and serial.. that needs testing and hence why the Zok pcb has been busted out. Fortunately, it works like a champ, so I can just clone the circuit from the Zok schematic over to the ZZ r4 or rr3-shield projects, and away we go.

So, part libraries.. down. FTDI USB test .. down.

Time to finalize the goal for the shield, and get that schematic laid out, and then the pcb layout, then print to paper to verify against a ZZ r3 pcb, and send to the boardhouse for etching … fun stuff!

Assuming I go down the shield route, it'll break out most of the features the ZZ r3 already offers, but more conveniently; keyboard, SD, etc will all be on there, and maybe link over the i2c and SPI headers and so on. The end goal is .. given an r3 pcb, and clip on the shield to top or bottom of it, it'll be able to run with just a USB cable from a computer or wall wort. Add on a VGA monitor, or speakers, or keyboard, or cart, or SD or whatever you want, and it can do useful (?!) work. No more piles of jumpers or external power pcb needed.. just nice and clean, like a raspberry pi or other modern board. Plug and play!

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/home/skeezix/public_html/zikzak.ca/zikzak.ca/dokuwiki/__data/pages/blog/ftdi_usb_-_serial_and_zok_testing.txt · Last modified: 2017/11/11 02:58 (external edit)