Wednesday, April 20, 2011

Tf-alpha-card stub...

Way too busy to post much lately but I finally decided on the minimal elements of the card for the tf-alpha bus so I setup blank board as a template.

I'm using a little msp430 as the board power controller (on the backplane I2C/TWI bus) that is always powered itself for supply1 through a 3v3 ldo.  I added links for an electrolytc cap (may or may not be useful depending on what goes on a particular board) but it's isn't necessary all the time.  It's easy to add to the 3v3 access traces though...  As usual there is a spy by wire access port and a jumper set to power the msp430 through the access port or the onboard regulator.  I did add a power led for the 3v3 line since it could have large caps on it and so a vivual check (and an automatice drain) is nice to have...

Of course the pinout for the card looks the same as the bus connectors... (96 pin DIN41612 Type C)

I kept the pins facing the inside of the card area available for use... The programming on a given card will determine how they power up and enable parts of the card.  It isn't necessary to use a 2x31 series chip though (but I like the ADC availability so I use them in the layout).

The regulator for the msp430 needs to always be enabled (or the control mechanism won't be available of course)...  All the other supplies on the card ought to be under the control of the microcontroller though... (again, the 330uf cap isn't needed, but could be useful to have in the layout depending on the design and since it's basically free to include the holes now...)

As you would expect, a template ought to be mostly a happy copper plane... I routed the supply1 connective links on the farthest side (near the backplane).  There are two regions of pour near the voltage regulator that I restricted to adjust the return current pathing but otherwise it's happy copper land.

On the back you can see the I2C/TWI lines (far to the outside since they are much lower speed and probably noisier than what's coming on the boards later.  The enables (mater and unique) get routed between some pins and along the outside (but remember they are basically on/off and won't switch much so interference either way shouldn't be a problem here.

Just a tiny post and not all that interesting, but the files are here and it does serve as a good template for the series of cards coming.

The goal of the Tanukifu project is to build a flexible and open set of tools to explore system development for purely educational/academic reasons.