The 33887 is a friend of mine, I agree with G.
I'm having a hard time reviewing it because not all the part numbers are shown. Capacitors are notorious for being a pain in the butt for reviews - their rated capacitance only tells you 20% of what you need to know. Also, more capacitance is more better, especially when you are prototyping.
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Originally Posted by AustinSchuh
If I remember right, the motor driver chip, a sn754410, is rated to 1 amp per channel and has 2 channels per chip, so I'm wiring both sets of control lines and outputs together to increase the output current so that I have a safety factor of 2, rather than 1. I can do that without problems, right?
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In the world of current sharing, 1 + 1 hardly ever equals 2. One leg will end up taking slightly more of the load than the other, so 1+1 might equal 1.8 or 1.9. This uses a BJT (Darlington) output, which doesn't share current as well as FETs do.
Personally, I'd bring them out separately and provide a simple way to common them together - what if you want to drive 2 smaller motors?
Quote:
Originally Posted by AustinSchuh
I'm mostly worried that I've got the 3 regulators hooked up right, the crystal hooked up right, that I've got the LEDs set up with the correct resistors. It's easier to work on debugging the rest of the circuit when the basics work. I based all that off of other schematics that I found online, but I'm more of a ME than an EE, so I don't know if I did it perfectly the first time.
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You should be sure to include easy ways to attach scope probes - Keystone makes a lot of test points just for this purpose.
Quote:
Originally Posted by AustinSchuh
I included the 5 volt regulator to power some of the 5 volt peripherals I plan on connecting, like some nice 5 volt encoders I have. The controller says "5 volt tolerant digital IO" on the data sheet for some of the digital input pins. That means I can connect the 5 volt encoder up to one of the 5 volt tolerant pins without problems, right? Or would it be better to set up a voltage divider to step the voltage down to 3.3?
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Page 22/32 of
http://www.nxp.com/acrobat_download/...01_02_03_3.pdf indicates that you can handle up to 5.5V on an input - a standard margin. You should be fine with 5V
inputs - the encoder will be fine. Driving 5V outputs is another issue.
Quote:
Originally Posted by AustinSchuh
I plan on daisy chaining a number of these together, hence the two power connectors and two RJ45 connectors. They will then provide a similar role as Jaguars over CAN for FRC. I plan on implementing a bus kind of like I2C or CAN over the RJ45 connector where the bus is pulled high with a pull up resistor, and all the devices pull it down to change the bit low, and read the bit back, floating the line, to set it high. I think I've got that part set up well enough that I can deal with it later.
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Why not use CAN or I2C? No need to go custom here.