Well it's been way too long since the last post but I've been flat out. I've been testing a range of new components that we want to use in our project board. The idea is that we prototype each of the various sub-circuits to make sure we don't end up with any surprises when the first proto pcb comes back. So far its proved a very fruitful exercise.
One of the devices I had to check out was a 2W audio amp. Now apart from the poor english in the datasheet (Example: When driving a speaker load suggestion set to the BTL mode for get the more power output.), the application circuit was drawn with the shutdown connection wired ON - i.e. to VCC. So without thinking, that's how I wired up the test circuit. When I got nothing coming out of the amp, I probed a little further, went back and read the data sheet, and realized that ON meant the shutdown was on, not the amplifier was on. Shutdown ON = amplifier OFF!
A quick rewiring of that pin and everything came to life - and quite impressively too. Given the mistake I made, I checked over the circuit that our hardware guy had created and sure enough, he'd been tripped up by it too. So it was well worth doing the quick prototype.
Next job was to test out the quality of some low priced speakers. They were tiny surface mount things and they sounded crap! I'm glad we did that check because it would have been a real let down if we'd gone ahead with them. It forced us to probe a little further and our sourcing guys found some great little beasties for about 70c each. They are 30mm across and use rare earth magnets and boy they can pack a punch. Unfortunately I don't have the specs on them just at the moment but I'll post a link later on.
I checked out a few other components such as an SPI-based Real Time Clock and One-Wire ID chip. Fortunately there were no surprises there but I've got to say, using Altium Designer to do the testing was a real breeze. They already have software drivers for SPI and One-Wire devices so it was pretty easy to get some basic test applications up and running.
So it looks like we are just about set to begin developing our first reference design. We had a brainstorm yesterday and came up with over 50 project ideas. But as we narrowed it down, we didn't want to spend all the time on developing the application. We wanted a project that would let us demonstrate the way to approach building a system without getting bogged down in the detail of developing a complex application. So it looks like the project will be a Natural Disaster Reporting System. The basic idea is that these units can be installed in people's houses and will log weather data back to a central site. In return, that site can send emergency response information back to the units based on immenent danger from fires, hurricane, tsunami etc. It'll give us a chance to show how to interface to a number of IO devices as well as build a nice user interface for the LCD and perform some Ethernet comms. I'm looking forward to building it.
Oh, and as a very topical side note, we drove down to Melbourne last weekend and had to drive through some of the areas affected by the bushfires. We weren't trying to be nosey but you can't help but notice the huge devastation. There are warnings that the weather tomorrow might be pretty bad as well and my mother in-law is going to evacuate just to make sure. No one wants to take any chances after what happened three weeks ago. So maybe our little project might get some people thinking about ways to use technology to better manage people during Natural Disasters.