Previously: New Project: GSM Motion Sensor
The Passive Infrared Module is tiny. Maybe 1" by 1.5".
And the SIM900 came, too. Looking more closely at it, there's a lot of stuff on that board. I started thinking, "It must take a lot to power all that. Did I buy two different wrong things?"
And the SIM900 came, too. Looking more closely at it, there's a lot of stuff on that board. I started thinking, "It must take a lot to power all that. Did I buy two different wrong things?"
My plan was to first get my old MSP430 working – one that I bought in 2012 – then worry about the new one, and finally work on integrating the SIM900. I looked for Code Composer Studio, the MSP430 development suite and I found out it's not supported on OS X. But wait! There's a beta for OS X. I looked into the beta and found out that it doesn't support my first generation MSP430.
Three year old software usually works just fine. Even 20 year old software works fine on emulators. Why doesn't three year old hardware work fine? Electrical engineers, I'm looking at you.
Trying to be positive, and remembering that I've invested money in this, I figure I'll move on to the new MSP430 (with the integrated PIR sensor). I start looking for the pins to connect, as my wife's cousin John had suggested on Facebook. They don't exist. You need a special $70 JTAG programming tool from the manufacturer to program the device. Or a different one for $115. More frustrating is the fact that there's a base standard for how to implement JTAG, but different manufacturers expand it in different ways, then charge you an exorbitant amount of money for their specific JTAG programmer. Not only can I not start small on a known introductory system (my old MSP430), but I can't even start on the more challenging device.
The Olimex PIR device didn't even have the jumpers its manual advertised for switching between TI's JTAG implementation (Texas Instruments designed and manufactures the MSP430) and Olimex's JTAG implementation.
The "jumpers" are solder bridges. I don't have a 220V soldering iron, so there's no chance I'll be fixing those soon. Plus I'm not sure I want to buy one that's high enough quality to solder these 1.5mm x 2mm pads right next to an extruded plastic component.
I went back to Facebook to gripe / vent / ask for help and luckily my old National Instruments coworker Craig was able to point me the open source hardware project called Armstrap developed by another NI coworker, Charles.
After a couple emails back and forth with Charles, I decided to buy an Armstrap. I had it sent to my dad's and I'll get it in two weeks when I visit the US.
The Armstrap is built on a different architecture than the MSP430. It's got an ARM microprocessor (CPU), specifically the Cortex M4. The ARM architecture is targeted at a bit of a different market segment than the MSP430.
The MSP430 is very low-level. The processor on the PIR device I bought is only 16MHz, which is about 160 times slower than the modern laptop processor. And there's only 2KB of RAM to hold your program (that's about 14 tweets). But for such a weakling processor, it consumes a minuscule amount of power: about 3mA when active and 0.5µA when sleeping.
For comparison, a standard smart phone battery provides 2800mAh (2800 milliamps for one hour), so the MSP430 in active mode would last 39 days on a smart phone battery running at full power. In theory it'd last 600+ years in sleep mode on a smart phone battery, but realistically it'd be much shorter than that, but still over a year.
The ARM on the other hand is a bit higher level. It's processor runs at 180MHz and consumes about 18mA when active and 12µA when sleeping. It's got more RAM (192KB - 256KB). Thankfully, almost all of the time will be in sleep mode. In theory, that's only 26 years of sleep mode. Practically it'll be much shorter than that, but I think it'll still be over a year. So I think the Armstrap will work for me.
Previously: New Project: GSM Motion Sensor
Next Update: Getting the Armstrap (est. Thanksgiving)
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