I need to see if this schematic is correct to use an Atmel 644p standalone with the Arduino IDE. I have went over several schematics with a MAX232 but, some have resistors between the USB jack and MAX232. None of them explained why they are needed.
Any advice and constructive criticism is welcome.
Thanks!
I think you are terrible mistaken in your proposed use of a MAX232 type RS-232 to TTL voltage converter chip to use as a USB type serial converter chip like a FTDI FT232RL. The USB connections to a PC can only be used with a chip that can enumerate and function as a USB device, which a simple voltage translator chip like a MAX232 is most certainly not.
Lefty
Caps on MAX232 are not correct.
Should be 5 total - you only have 3.
MAX232 does not do USB to Serial - you need a part like FT232RL for that. See www.ftdichip.com
I would suggest a module like MIKROE483 from mouser.com $11
Also FTDI Basic or FTDI Breakout board
Or CP2102 module from e-bay, use the BATI kind that have DTR available at a breakout hole.
MAX232 will output +/-10V signals, and expects the same back. As drawn, T2out will blow up the Rx pin. And R2out will likely damage a PC if connectedl.
Put a diode across the reset resistor - anode to Reset, cathode to +5v.
What does cap C9 connect to when the jumper is closed?
C4 should be bigger, like 1 or 10uF.
C8 can be 1uF.
Add 0.1uF caps to the VCC, AVCC, AREF pins, as close to the pins as possible.
Can draw the VCC/AVCC parts next to C5.
JP5 - RTS should be DTR, I imagine you want it going to C9.
Check the order of the pins, make sure an FTDI Basic, or FTDI cable can plug straight on. I always double check against the ProMini schematic to be sure.
Flip over diode D1. The intent is for any spikes/etc. on the reset line to get bypassed into the Vcc line.
Planning to connect some external parts to this? I would add another header or other means to connect +5, Gnd to off board devices.
The FTDI and AVR header can be used as well.
CrossRoads:
Flip over diode D1. The intent is for any spikes/etc. on the reset line to get bypassed into the Vcc line.
Oh, ok... Must have misinterpreted what you wrote...
Planning to connect some external parts to this? I would add another header or other means to connect +5, Gnd to off board devices.
The FTDI and AVR header can be used as well.
Yes, I wanted to get the basics first. This board is to experiment to see how the 644 will do in a bigger project. Wanting to learn more about standalone micros before I make any PCBs for the larger project.
Thanks for your help CrossRoads.
