Yep, that's what I said. A2 = SS = CS. The resistor is implied "in series" as I'm talking about things. Adafruit may do it that way, but here you have three devices on the SPI bus, so how are you going to see R/W activity when talking to the FRAMs? Seems like the easiest way to do it would be just tie the resistor to GND. Also, I don't see any reason to not tie the resistor to GND unless you actually want the LED to only indicate SD card R/W access.
If you are prototyping this first... then you'll need the vias exposed so you can solder a wire through each via. And as long as you are hand soldering everything you won't have to worry about shorts... that's typically an issue when you're NOT looking at each connection.
It looks a lot better already, but if you want me to see what I can do with it email the sch and pcb to technobly a t gmail d o t com
Also, what is the part numbers for each of the components.. so I can double check everything.
Lastly, you connected the CS lines to the I2C output of the Core xD... (D2 - D6 is much better).
Itās going to show if you are selecting the right device. If your CS is HIGH, and the CLK is pulsing, you wonāt see the device LED blinking. Thatās my understanding of why itās there
I got the other 2 LEDs in as well based on the same concept:
That would make sense if you had 3 separate LEDs. But here you only have one. I don't see any reason to add 2 more though. R/W is R/W is R/W. It's probably only useful for the SD card so you don't eject it while it's in the middle of a R/W operation, but there's no telling WHEN the next R/W operation is coming... so it's pretty useless all together. Think of it as a FUN item. So for maximum fun, connect the resistor to GND.
Ok ... but it's still only connected to the SD card. Is that what you want??
Also, let's say the LED doesn't light... now what is wrong? It could be the CLK is not toggling, OR the CS line is not pulled low OR both!
Proof that the SD card is working relies way more heavily on it actually transferring data.. not just the SCK and CS lines toggling so I don't really see that as a debugging tool.
Well your file contained a few extra LEDs to route, which I donāt think are necessaryā¦ but hereās an attempt at routing them all.
All components are on the TOP layer.
It occurred to me when I was done you should probably have included 0.1uF decoupling caps near the FRAM chips. Iām not liking the āsceneā there now for adding some caps. Bah.
Oh also that pull up resistor on the Card Detect pin doesnāt go anywhereā¦ Iād say it should probably be removed rather than tying up another digital input. I kind of placed it such that if you remove it the routing doesnāt get all messed up.
Hmmā¦ Iāll leave that part to you I tried to keep the vias out from under the SD card holder to prevent shorts. Might be hard not to put one under there now.
Donāt forget to label the LEDs nicely { SD FRAM1 FRAM2 }
After placing your components, you always want to plan out how you are going to route your power and ground first, and roughly sketch something in so you don't have issues later on just trying to get power to everything properly. As I was doing this, I noticed that it would be wasteful not to just plop down a ground plane under the hi-speed memory devices. It will help get a ground connection to all devices more easily, and it can also help to reduce EMI and improve signal integrity... in this case I think it mostly just makes it easier to get GND everywhere. Notice I didn't route it down past the memory chips, because I don't want it really near the antenna of the Core (even though that does sit up a good 1/4" away from this board... it's still better to not have it there).
And copper is free... so you might as well use it if you can, and it makes the board look more professional if for no other reason.
You can also use ground planes (with hatched patterns) to fill in area of your board that don't have a lot or any components to help distribute heat across the board properly during reflow and/or wave soldering. Without that, sometimes the board can warp like a potato chip. This is more of a problem for larger boards though.
Nice stuff here! Itās good that you guys are teaching me so much. I guess no one ever knew how much effort is poured in making such stuff that looks simple for that matter
Iām kinda proud of the board even before itās made
I used Eagle CAD Pro 6.4.0 but I have 6.5.0 to install when I get a chance.
Pours are very easy, you just use the Polygon tool and draw a shape about where you want it to go, then edit the properties and set the Isolation value (distance between Nets that are not the same as the plane). Then use the Name tool to set the net name of the plane (GND in this case). Itās easier not to try routing with ground planes in place though, because you always have to refresh them to see what changes you making to your tracks. It kind of gets annoying after a while.
You can effectively clear out the filled areas of the polygons by saving, closing and re-opening your PCBā¦ or the better way, select the Ripup tool and click just outside the boarder of your design. This will remove the fill, and if you want to check it again just click the Ratsnest button. BTW, these two operations are not intuitive at all. Better layout software will have an option to disable ground plane fills or to turn them into different views to make it easier to see things.
