It looks like you added a switch and push button between RC1 and R130. Connecting to RC1 makes sense because that is connected to the reset PIN (PORST_N) which we are trying to short and it is larger than the neighboring resistor R906. What I don’t understand is why you picked R130. Could you have connected the other wire to any ground point including a large heat/RF shield? Is there some reason why you picked R130?
The switch is for RC1 to reset for spi. The pushbutton is for R130 which you’ll encounter later in the labs.
I reached the part of the labs where ANT_TRN is used so R130 makes more sense. As a student, the button and switch you soldered on make things easier since I don’t have to solder but they also make things harder from the perspective of understanding what you did and why you chose those points. The attached accessory board covers up part of the main PCB and it is not easy to see where it attaches to exactly since the solder blobs are larger than the surface mount components they attach to. I’m trying to understand the general principles of where I need to solder these connections so that I can apply the concepts to other boards besides the example from class.
Could the reset PIN (PORST_N) have been connected to any ground point on the board or did it need to go through a resister first to reduce the amount of current? It is not clear if you chose RC1 due to easy access since it is a large component or because you needed a resistor before you shorted out the connection. Also, it is not clear if you soldered this to a ground point because I’m not certain what you connected this to.
Could ANT_TRN have been connected directly to any 3.3V pin on the board providing power? If so, then would a resistor be required like the one at R130 or was the resistance inconsequential and you just needed an easily accessible point connected to ANT_TRN? It looks like R130 (ANT_TRN) is connected to RC1 (PORST_N) but I can’t tell for sure. Are these the two points you connected and what was the reasoning behind choosing those two points instead of any random ground or 3.3V power pin?
The objective in both cases was to apply a voltage (0 or 3.3) to the relevant pin (PORST_N or ANT_TRN).
Any ground and 3.3v on the board would work just the same. We’re not ‘powering’ anything (flashing lights, calculating, etc) with this, just pushing or pulling enough electrons to register a logical high or low voltage, so we don’t have to worry about power consumption.
The other issue is that the DQFN (dual-row quad flat no-lead) package is pretty fine pitch, so it’s hard to probe it. That’s why i went for the resistor and capacitor - they’re MUCH bigger, easier to probe, and easier to solder to. I soldered to the cpu-side of the resistor, so the voltage I apply isn’t going through it.
I’ve added a to-do for me to to put together a better explanation of the modifications i made to the board and why.
P.S. apologies for my delay in responding! somehow my email alerts on this message board got disabled…