Quote:
"I'm determined to put a micro-USB B plug on my PCB, and whatever chips I need to program the Mini via pins 1-3."
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Why do you want to put a micro USB on your board? Your linked Sparkfun breakout brings out Tx, RX and GND. Solder a pin header to these connections and connect to your Mini board with breadboard style jumper wires (female to female) to another 3 pin header. At this point, you now have TX, RX, GND on your Mini board. TX and RX must now be inverted before connecting them to Mini pins 1 and 2. You now have two options:
(1) invert TX/RX in the FTDI firmware
(2) Use the SN74LVC2G14DBVR to invert with hardware
It sounds as if you simply want a dedicated programming port. In which case, option (1) will provide the simplest solution. If you invert in the firmware, you will have turned your TTL cable into a RS232 cable. Mini pins 1,2,3 can now be connected directly to the 3 pin header.
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Quote:
"What if I combine the FT232RL chip (from the breakoutboard above) with a gate inverter? That would do it, right? So I'd connect the PC->micro USB B->FT232RL->gate inverter->Mini pins 1-3."
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Yes, but why duplicate the functionality of a USB to serial adapter on your Mini PCB? All of the components you see on the Sparkfun breakout would now be moved to the Mini. The only advantage I see to this is a prettier hookup; e.g. no breakout at the end of your cable. If this is the case, get a FTDI cable with different terminations and use a keyed 3 pin JST connector on your Mini PCB,
http://www.ftdichip....SBTTLSerial.htm
I think Adafruit sells one cheaper.
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Quote:
"I do not have a logic level analyzer, so I'm having some trouble verifying the levels in the cables I've got here. Is the TTL Port in your schematics the same levels as in a standard USB cable?"
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You don't need a logic analyzer; just a multimeter/voltmeter. Plug in the USB to serial adapter to your PC and measure the voltage from TX to GND. You should get a reading of 3.3V or 5V if it is TTL (depending upon the adapter) and 0V-2.4V, if RS232. My USB to serial adapter is 5V (TX/RX) and I use the 5V output for VCC of the inverter.
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Quote:
"I tried finding the 74LVC2G14 on Farnell, but didn't find a direct match. What about TI's SN74LVC2G04DBVR?"
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You want the SN74LVC2G14DBVR from TI. I think the designation is unique to their Little Logic line of parts. It's widely available (Mouser, Digikey ...) The part with extra gates is 74HC14 If you have a .com or .edu address and register with TI you can get free samples.
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