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Building an AVR Development Board-A few questions.

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lord loh.

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I am building a general purpose development board for the AVR. It is a bit like the breadboard, but with hardwird VCC, Gnd etc and a mounted dip switch, LEDs and a few microswitches (push buttons).

I would like to add RS232 interface using MAX232 and also a circuit for driving stepper motors. I did start with Nigel's Tutorials - Hardware section.

The blocks that I find are...

1. The MAX232 circuit has 2Tx buffers and 2Rx buffers. The RS232 interface uses just 1 of each. At https://www.pjrc.com/tech/8051/board3/schematic.html, these guys have put 2 RS232 interface. Is that all that is needed? Is the MAX 232 designed with 2 RS232 (DB9 subset) interface in mind. Are there other ways of using the MAX232?

2. Can a stepper motor driver circuit be implemented using the L293D dual half H-Bridge ICs? Can such a circuit drive any stepper motor?
 
lord loh. said:
I am building a general purpose development board for the AVR. It is a bit like the breadboard, but with hardwird VCC, Gnd etc and a mounted dip switch, LEDs and a few microswitches (push buttons).

I would like to add RS232 interface using MAX232 and also a circuit for driving stepper motors. I did start with Nigel's Tutorials - Hardware section.

The blocks that I find are...

1. The MAX232 circuit has 2Tx buffers and 2Rx buffers. The RS232 interface uses just 1 of each. At https://www.pjrc.com/tech/8051/board3/schematic.html, these guys have put 2 RS232 interface. Is that all that is needed? Is the MAX 232 designed with 2 RS232 (DB9 subset) interface in mind. Are there other ways of using the MAX232?

The extra two are intended for handshake lines, but it's perfectly OK to use them for another serial port.

2. Can a stepper motor driver circuit be implemented using the L293D dual half H-Bridge ICs? Can such a circuit drive any stepper motor?

You don't need H-bridges for uni-polar motors (the most common type), just simple transistor drivers.
 
lord loh. said:
2. Can a stepper motor driver circuit be implemented using the L293D dual half H-Bridge ICs? Can such a circuit drive any stepper motor?

If you build up a bipolar stepper motor driver, it'll be able to drive both common types of steppers (unipolars either get half a winding disconnected, or both windings used in series). There will be some uncommon types (5 phase, etc) that won't be usable.

James
 
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