Chief Delphi - Custom Circuit Design

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Re: Custom Circuit Design

Quote:

Originally Posted by 114Klutz (Post 711117)

This isn't considered anything especially complex to do - nor is it unique. Even if the ICD2 header was open, and someone reversed engineered it, people would be required to purchase and use the KOP boards anyways, and I haven't heard of anyone buying the RCs separately for use in other applications.

I have a feeling that they may use the i2c bus to handle communications with the modem. If this is the case and they exposed a header to connect to it, then it would be theoretically possible to interfere with this (either accidentally or intentionally). This might allow a robots output to be active while in disabled mode, which would be a large safety issue.

Re: Custom Circuit Design

Quote:

Originally Posted by manderson5192 (Post 709543)

All right. So I looked at the documentation for the gumstix robostix and the number of external interrupts that are connected to pins is to small. Thus, I have decided to use a MEGA AVR (don't know which one yet). This means we will have to build our own circuit board. Does anyone have suggestions for how to go about designing, building, or implementing a board? Should I go for perfboard or order a PCB per a design that I make? Is there a free CAD software I should use? What about outputs from the board: should I provide other connections than just the no-brained TTL/RS232? I really want to have a prototpe that might work with next year's control system.

Any suggestions/comments are very much appreciated! I so intend to document the prototyping project and make it nearly entirely open-source so other teams can learn to do this too...

I would definitely suggest making a PCB over doing a perfboard because it will be more compact and reliable, not to mention look better. A perfboard may be better for your initial prototype, however. I use Eagle for making PCBs. The interface isn't the greatest, but you get used to it. As for outputs, I would recommend having several indicator LEDs, an LCD, I2C, UART(with and without level conversion), and SPI.

I attached the schematic of the motorcontroller board from UW-Madison's entry into the Intelligent Ground Vehicle Competition last year. This board was designed to interface between a laptop and Victor 883 motor controllers. Some of the specs: It had an ATMEGA16, now it has a 32. It has an 8 bit parallel data bus to communicate between the quadrature decoders, latched LED bar graph and LCD. It has a software controlled PWM source select so we can switch between input from an RC receiver and the AVR. It has an RS232 port for communicating with the laptop. We use avrdude to program it. If you insist on using windows, you can use AVR Studio or WinAVR. If you are interested in the board layout or software let me know.

-Ken

Re: Custom Circuit Design

Quote:

Originally Posted by manderson5192 (Post 705969)

-Is it worth it to instead build the entire custom circuit rather than buy
-Matt

Functionally no.
Will you learn more? Yes

Re: Custom Circuit Design

Quote:

Originally Posted by Ken Leedle (Post 711456)

I attached the schematic of the motorcontroller board from UW-Madison's entry into the Intelligent Ground Vehicle Competition last year. This board was designed to interface between a laptop and Victor 883 motor controllers. Some of the specs: It had an ATMEGA16, now it has a 32. It has an 8 bit parallel data bus to communicate between the quadrature decoders, latched LED bar graph and LCD. It has a software controlled PWM source select so we can switch between input from an RC receiver and the AVR. It has an RS232 port for communicating with the laptop. We use avrdude to program it. If you insist on using windows, you can use AVR Studio or WinAVR. If you are interested in the board layout or software let me know.

-Ken

UT-Austin also did a similar microcontroller board (designed in eagle) that interfaces to Victors 883 and a laptop using a 9S12C from technological arts. We did a serial master communication from the laptop to control PWM, encoders, sonars and various switches. If you want to see pictures of the various robots , see the IGVC photo gallery. Our documentation is not as clean as Ken's and I don't suggest other teams to use the 9S12 unless you've been trained on the architecture. We use that microcontroller in our classes and freescale donates quite a bit of the hardware.