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• More Soldering

  jacksonliam • 03/11/2016 at 17:47 • 0 comments

  If you look closely at the module in the picture you can see that 4 resistors on the top left of the module are missing, on the other modules I have they are not missing! So I must've blown them off with all my hot air. There's also a bit of toombstoning on the RF capacitor and 0Ohm resistor which wasnt good.

  So I tried again, This time I didn't tin the pads for the module, Just a massive puddle of flux. I tacked a few pads in one corner with a blob of solder while pressing the module in place. I then started dragging solder around the module and surprisingly few of them bridged! It was like magic! The ones that did bridge cleaned up nicely with a freshly tinned tip. The GND pads were the trickiest, assumingly due to being more heatsinky and I was very careful not to bridge onto the passives on the module itself, which are quite close to the edge.

  I made sure to get the RF resistor and capacitor nice and flat and I'm really happy with the results. I've probably only soldered 200 components and I'm sold on 0603 now, so much quicker and less hassle that through-hole!

  I'm certainly going to build a reflow oven at some point though because so many interesting parts are in BGA or QFN.

  This one picks up lots more neighbouring APs than the first one :D
  

• Crowded 2.4Ghz or Troublesome Drivers

  jacksonliam • 03/02/2016 at 08:57 • 0 comments

  My router wouldn't go into 40Mhz bonded channel mode due to neighbouring networks on channels 1,6 and 11. I tried to get the neighbouring AP on 6 to change channel by temporarily running APs on 5 and 7 but that didnt work. As I wanted to use a channel 7+11 bond. 'sharing' a channel with another AP works, being on an overlapping channel should/does not.

  The module did connect at 72.2Mbps in 20Mhz mode which is better than the ESP8266 board did (though the ESP board should in theory support that) and managed throughput in the region of 40Mbps, no improvement over the ESP8266 module.

  I wanted an AC1750 router anyway and my new router happens to have a naughty '40Mhz only' mode. This allowed the module to connect at 150Mbps but didn't help with the throughput as about twice as many packets were dropped as not.

  I can't say for sure if the dropped packets are from interference due to forcing 40Mhz mode, the RF layout of my board or the driver. I've tried a few drivers (e.g CHIP one) but the hadess one appears to be the most stable.I've tried 4.1 and 4.4.1 Pi kernels.

  But what this has really told me is I need to find a dual band 5Ghz chipset and dual band antenna. Let me know if you have a better idea than a U.FL connector and something like this.

• Soldering the prototype

  jacksonliam • 02/29/2016 at 23:12 • 0 comments

  I ordered from OSHPARK and to the UK they're just as slow as the Chinese suppliers that give you 10 boards for the same price, so I probably won't use them again.

  The module was so tricky to solder compared to the ESP8266 ESP-12F. The castellated pads are too small to do individually with an iron. I managed to lift the bottom most pin on the left (luckily NC) trying this.

  In the end I fluxed and tinned all the pads using the drag method, then fluxed the bottom of the module, aligned it and applied light pressure on top with my tweezers, then directed hot air at the pads and the solder melted and the module sunk into place. Probably not the best way to do it, i think it really needs to be reflowed but I might try the 'blob and suck' method I've seen used on QFN chips on the next one.

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