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Adding RF to my Treadgaming project

Discussion in 'The Projects Forum' started by Chillance, Jun 10, 2013.

  1. Chillance

    Thread Starter New Member

    Jun 10, 2013

    I've been working quite a long time on my hobby project I named "Treadgaming". It's about making exercise more fun. So, I mixed a treadmill with gaming, ending up with "treadgaming". You can read more about it on the blog http://treadgaming.blogspot.com/ (although it's currently not updated as often as it should be, because I spend most of the time actually working on the project).

    Anyway, I've made a PCB that basically contains a microcontroller and a high end laser sensor. Works fantastic! The firmware I had made recently makes it really awesome filtering and calibrating the noisy data! I tried in games, and works nicely. When testing though, I realized that I really need an easy way to look around and interact, and eventhough the PCB has headers, the microcontroller had TWI/I2C limits (no hardware support), which made using a Wii Nunchuck problematic. So, I figured I update the board, which is where I'm at right now. And, while I'm updating the PCB, I figured I include a RF chip because might want to design some neat Nunchuck type of control myself later, but with more/better hardware on it, which then could communicate over RF, skipping the cable. Or anything else cool. That would be 3d printable as well, like the enclosure I made for this as well.

    Now, all I know about electronics is by self-learning doing this project! So, I need help with the RF design! Currently I have 2 PCB layouts I need feedback on. Now, I know that the chip antenna needs to be separated from the rest to avoid interference. Antenna pins should also be as close as possible to the nRF24L+ chip. The question I have here is how much really. If you take a look at the first image ("treadgaming_rf_more_compact.png"), I have those long pads (for out-of-box support of Nunchucks) above and below there, with the RF ( nRF24L01+ ) parts in the middle. The layout of the RF components actually follows what Sparkfun did here: https://www.sparkfun.com/products/691 which also follows the reference design found in the nRF24L01 datasheet. The second image ("treadgaming_rf_more_separated.png") is the same, but the Nunchuck parts moved further to the left. The biggest question here is, can I use the first more compact layout, or should I go with the second one? Or something else? I really prefer the compact one obviously, but I'm not sure if the large pads might cause RF issues, and if they are too close? Also note that GND doesn't fill under the antenna chip, just like the other designs.

    Any other feedback/comment is also welcomed! Such as having the width of the trace for the antenna as wide as possible (that is, so it matches the 0402 pads)?

    Also, I hope this is not seen as spam, as I might want to sell this later as well.