While working on my ENC28J60 Project with the PSoC3 FTK,I felt a pressing need to get some debugging data out,in realtime(dont wanna pause it >.< ).There are a few direct solutions,
1.LCD
2.Serial Interface(UART)
LCD can be run at 3.3(here) but its too many wires,and limited text.That makes UART our preferred option.Which explains the title,TTL-UART.
PSoC Creator has a UART component,which can output RX-TX lines(TTL) to the GPIOs on the underside.Hunting around on the net,there are a couple of solutions.Keep in mind,that these will be 3.3V signals.
Before we discuss various options,Serial Port interfacing is basically about turning a 0-3.3V signal to a +/- 12V signal(Inverted) and the reverse for RX.
1.Use a dedicated chip.
MAXIM Semiconductors has a dedicated bunch of chips,each with different features.The one we'd need is the MAX3232(
here).Its a one-chip solution,with only some decoupling caps externally.Make a neat PCB,and we're done :)
Sadly,this isnt a common chip here(unlike the MAX232),and ordering is costly :(
2.Use a popular "2 Transistor" Solution.
This is another popular method,which involves basic NPN and PNP switches based on the 3906 and 3904,though there are variants around.(
a detailed explanation of this circuit)
3.Bring in the MOSFETs! :)
Another solution uses a 2N7000,an N-Channel FET.Images,PCB and more
here.
4.Use the
MSP430 Launchpad(or similar)
If you do have an existing board which has some kind of TTL to USB/UART interface,get it out,and rig it up with the FTK :) .. A messy arrangement,what with 3 boards(Ethernet module too :P ) but it works.Even a PSoC1 Eval kit is a candidate here.
5.Use a MAX232
Yes,this 5V chip can be run at 3.3,to no special side effects,and with perfect results.However,this is abuse of the chip,and shouldnt be used for production level designs.
6.Use a FT232RL or similar USB UART IC.
This chip is another great way to approach this.More at the SparkFun store,
here.
7.Mod an existing USB-Serial Cable.
The title says it all.Details
here and
here.(Many such on the net)
8.Use OpAmps :P
This was an Idea i thought of as I was reading the RS232 specs.It blared comparator at me,since a 0-3.3V signal,needs to be inverted and made a -12V/+12V one.While you can use a dedicated voltage comparator chip,or wire a 741 as an inverting comparator with hysterisis,both should work.How about using the analog blocks on the PSoC3? :)
9.Quick & Dirty : A Hex Inverter
Use a hex inverter for a quick and dirty solution.But its success depends on how far you can violate the standard RS232 protocol.
I'll add more as I find/think of em.Take your pick :)