As promised in Circuits & Secrets, I have refined my original DTMF Decoder design to run off a PIC microcontroller. While I was at it, I made many other refinements, including a 510 digit non-volatile serial EEPROM memory. Information is stored forever, or until overwritten. I am considering manufacturing these, but first I'd like to see how well the prototypes sell. I had PC boards professionally burned for these prototypes. Here is a partial list of features:

• Will decode all sixteen DTMF tones
• Direct phone line hookup for unattended monitoring
• Space inserted after decoded numbers according to user selectable inter-digit gap time
• User selectable inter-digit gap time of: NONE, 4-sec, 8-sec, or 1-minute
• User selectable "Ignore" options
• Ignore a '1' when dialed first in a series
• Ignore 1+AREA CODE when dialed first in a series
• 510-digit memory (actually I'm now working on a 2048-digit version, which will be ready soon.)
• Low power mode when memory is full
• Will not overwrite memory until user resets or clears log
• Tones can be decoded via direct line from ham radio or scanner with optional cable
• User's manual explains how to decode tones recorded on tape
• No confusing "scroll." Page through memory 16 or 32 digits at a time, depending on LCD version you choose.
• Runs off 9-volt battery or 9-volt battery adapter
• Heavy duty 9V battery clip that won't fall apart after repeated use
• Low power consumption of ~10mA (~40mA if using 16x2 LCD w/ backlight -- DC adapter recommended in this case)

The features are better described here in the manual.
You can also download the manual in Word 97 format by Clicking (Netscape) or right-clicking (Internet Explorer) here.
Here's the manual in plain text format.
 
 

I am just a lone guy, not a huge company so I can't really offer an official warranty. Basically, if I get killed and your decoder dies too, I can't help you. Barring my untimely demise, however, if you have a problem with the decoder, and are willing to ship it to me, I'd be happy to repair it for you. If the fault was mine, I will not charge you. If you (or your dog) threw the gadget in the ocean and then dissected it in a fit of lunacy, well, then, I'd hafta ask you to cough up a sawbuck or two.

The production models, if I decide to run them, will sell for $149. I'll let the prototypes go for $99. The major differences between the prototypes and the production models are these:

• All Prototypes have 2x16 LCDs, unless you specifically request otherwise.
• Prototypes may be fitted with an LCD with dimensions other than that which the PCB was designed for. However, it will mount on at least two standoffs and be properly wired to the PCB.
• Prototype PCBs do not have a silkscreen layer.
• Prototypes may have some PCB areas that have been de-soldered and reworked (for prototyping purposes of course).

Other than the above, the prototypes are fully functional. See pictures for an idea of how they generally look.

SUPPORT ITEMS FOR PIC-CONTROLLED DTMF DECODER WITH 510 BYTE MEMORY

There's no complete DTMF Decoder Kit as of yet, but I do have a Support Kit available if you'd like to build the circuit yourself. The Support Kit includes the PCB, pre-programmed PIC, 8870 DTMF Decoder Chip, Schematic, 2-sided PCB Pattern and Stuffing diagram.

You may also purchase above items seperately.

Right now I'm only burning 3 boards at a time so they're expensive: $29 each-ouch! The price list for all items is below.

Click here for price table and buying instructions.

SUPPORT ITEMS AVAILABLE FROM THIS SITE

Below are some items available for download from this site. The manuals are kept here for convenience and the code is kept here in case anybody wants to modify the PIC to add special functionality to their Decoder (advanced users only).

User's Manual in HTML format.
User's Manual in Word 97 format.
User's manual in plain text format.
Manual addendum for home brewers
Parts list in Excel 97 format
Code for 2x16 LCD
Code for 1x16 (logical 2x8) LCD
 

Part	Does not Include Shipping & Handling
PCB	$29
Schematics, PCB patterns, Stuffing Diagram, Code, & other info*	$8
8870 Chip	$6
Pre-programmed PIC Please advise 1x16 or 1x32	$12
All of the above	$49.95