In SX Microcontrollers, SX/B Compiler and SX-Key Tool, robotworkshop wrote:

Hello Chris,

Actually surface mount chips are not that bad once you start getting use to them!  I too had an aversion to using them initially since I thought they would be hard to work with if I didn't own all the fancy surface mount soldering equipment.  With careful selection of surface mount parts and order of assembly it is possible to build these with the tools many people already have on their workbench!  One thing that makes a huge difference is having a high quality board with mask as the base to build upon since the pads are so fine for the CPU.  The SX48 chip is the first and hardest one to mount on the board.  I'll get it in position and then just warm one pin with a tinned soldering iron.  Before soldering any others I check the alignment with a magnifier.  If it isn't lined up just warm that one pin and adjust it.  Once perfect i'll tack down another pin on the other side of the chip and check again.  If all looks well i'll solder each side and let it cool before doing the next.  Then, go over each side with solder wick and let cool before doing the next.  The MAX232 goes on next and can be done the same way but I usually find that I don't need the wick on that one.  The remaining parts are easy!  I've documented a lot of this since which has come from other kits i've made in the past.  Schematics would be included with the docs.  A kit is a definite option (assuming there is enough to cover a run of boards) but i'd rather have the focus on the kit portion as a way for people to learn to work with surface mount parts.

It certainly helps to have an OEM type kit that is known to work to at least get you started on surface mount devices and also makes a great way to validate that you can actually use these Parallax chips.  I've got a similar layout for the BS2p40 OEM chip which i've used in a couple of my projects with fantastic results.  It too has a MAX232 for more of a true serial interface and if the EEPROM ever wears out I can just pop it out and plug in a new one!  That came out perfect.  I had started with that and then modified it for the SX48 so I could get the benifit from those chips as well.  When I started I would have picked up an OEM kit had one been available but learned alot along the way so it was worth it.  That's how I discovered that a real BS2p40 module would work if the TX and RX lines are reversed which threw me off track for a bit.

Best Regards,

Robert

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