Micro-controller Programming
MAS.863 -- Fall 2003

Notice

Assignment

Coding

Burning

Serial Transmission

Sample Codes

Applications

Resources

Changes to board layout

The original schematic can be found at: http://fab.media.mit.edu/topics/electronics/pcb/pcb_assignment.htm

Since then, the following notice has been released, please change your boards accordingly:

  Date: Tue, 11 Nov 2003 22:49:25 -0500
Subject: errata on the board design
From: r <raffi@media.mit.edu>
To: mas863@media.mit.edu

first, a lot of people are having problems programming their boards after they have stuffed them. if you plug your board in (from just the schematic you all have) -- you'll notice it is pulling about 0.062 amps @ 5V. that's way too much and it is preventing the in-circuit programming from doing its thing. you need a 0.1uF capacitor (the same as the other capacitors) from pin 6 on your max202 to ground (what you have now is that pin 6 on the max202 is shorted to ground). if you put that capacitor in, you'll see the current draw go -way- down to something more like 0.028 amps @ 5V and you should be able to program your circuits in place now. if your trace from pin 6 is visible, you can just cut it and put the capacitor across it. if its not visible, you'll have to do some hacking.

second, there seems to be some issues with the db9/serial connector that i chose. try this for a connector wiring

pin 14 on the max202 -> pin 3 on the DB9
pin 13 on the max202 -> pin 2 on the DB9
the ground line is fine

try these two changes out -- we have one data point that this fixes all problems with the boards (see the attached picture for the first working board).

much thanks to bb2 for his help and persistence in solving what is going wrong with most people's boards.

r