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I'm building a snail (regular) mail notificator using a cheap RF transmitter/receiver pair and ATtiny85's. I'm in the process of coding the receiver interface with a computer part. I discovered V-USB a long time ago and found it very interesting, but didn't have any use for it, now's the perfect time to learn how to use it by building it in my project. This is a personal and a learning project, all thoughts and ideas are welcome.

The snail mail notificator works on a very simple principle: a MCU is programmed to send a payload when a pin change interrupt occurs, triggered by the opening of the mailbox lid by the postman via a switch, the transmitter system consumes next to no power. Once the receiver gets the payload it will forward it somehow, the ultimate goal is to send an e-mail informing the arrival for regular mail via e-mail. How would one implement such a system with V-USB on the receiver side?

I have thought of a couple of solutions, but cannot decide on what's best:

• Use the HID keyboard example to send a key sequence (shortcut) that will invoke a script (configured by me) that sends the e-mail. The computer would be my Raspberry Pi media center that is always on anyway.
• Somehow make a receiver script (driver?) on the computer side that listens to the device. That however I don't know how to do yet.
• Poll the receiver to see if it has gotten any data recently using the HID data example.

Any thoughts or criticisms about my project?

If you only needs single button to use at the mailbox, why don't you use cheap wireless doorbell?
Monitoring mailbox using computer? How many mail you will receive in a day?
Just asking

declan smith wrote:If you only needs single button to use at the mailbox, why don't you use cheap wireless doorbell?
Monitoring mailbox using computer? How many mail you will receive in a day?
Just asking

It's not about monitoring the mailbox, it's about receiving an e-mail when I get some mail or a package - where I live we have 2 compartments in the mailbox: one for regular mail and a small compartment for packages. I went with the keyboard shortcut method. A similar emitter could be used to report on something else around the house, having the receiver connected to a computer makes it straight forward to interface with the web or whatnot.

Like I said, monitoring mailbox all the time... in this case you had 2 boxes (I assumed like that)
Sending the email was another thing... you can do it in many ways...

I will use multi button transmitter like Vehicle remote looks like... many choises from 2 buttons to 6 buttons as I know... they also use the free freq 315/433 mhz...
Inside the transmitter is 24 bits decoder which avoid to match others transmitter ...
So you only need to connect the output (on/off) of the receiver to your MCU, using V-USB to communicate with your computer (I'm using Delphi or C#) or Rasberry Pi (I haven't try this one)... after that is up to you how you want to send the email...

I prefer that transmitter because I don't have to think about power source... I only had to change the battery after 3 years... depends on how often you press the button...

About inside the house you can use your RX with the same MCU...


Just give you idea

declan smith wrote:I prefer that transmitter because I don't have to think about power source... I only had to change the battery after 3 years... depends on how often you press the button...

That is one of the main concerns of course, I will use an ATtiny85V-10 for the transmitter with a 3V lithium coin cell. According to Wikipedia a CR2032 has about 200mAh, I measured my transmitter circuit at 100nA (nano Amps!) when in power-down mode, so that's about 230 years of autonomy - realistically it will probably be something like 1-2 years, but that's already great.

compartments in the mailbox: one for regular mail and a small compartment for packages. I went with the keyboard shortcut method. A similar emitter could be used to report on something else around the house


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