Hi all,
I'm currently reworking an old touch-tone telephone, which involves redesigning the circuit to avoid the whole telephone line high voltage AC circuitry etc.
In my first prototype I got on fine using an IK semiconductor 91214b IC to do DTMF generation, with the keypad keys connected as inputs and the output connected to the handset speaker. However, it's relatively difficult to obtain
There will be a central microcontroller (likely an Arduino Nano or Pi Zero) and I could theoretically just use this for DTMF, but it would involve using up a bunch of I/O which I'd rather not!
Ideally, I'd like to have the DTMF generation on a separate chip, but I'd also like it to be surface mount so I can hide it away on the 'keypad' side of the circuit board and save the other side for everything else that will be eventually packed in.
However, I'm really struggling to find anything suitable, it seems they're mostly not manufactured anymore. There are plenty of decoders, but looking through RS/Farnell/Digikey etc I can't find any generators.
The only generators I've found have to be interfaced with an MCU (e.g. MT8888CS1), and I'm happy enough using something like this (it might even provide even more flexibility). But I don't know how I'd interface my 10 number keys with it, without using whatever my central microcontroller ends up being, so if anyone has any insight here that would also be appreciated!
Thankyou!
I'm currently reworking an old touch-tone telephone, which involves redesigning the circuit to avoid the whole telephone line high voltage AC circuitry etc.
In my first prototype I got on fine using an IK semiconductor 91214b IC to do DTMF generation, with the keypad keys connected as inputs and the output connected to the handset speaker. However, it's relatively difficult to obtain
There will be a central microcontroller (likely an Arduino Nano or Pi Zero) and I could theoretically just use this for DTMF, but it would involve using up a bunch of I/O which I'd rather not!
Ideally, I'd like to have the DTMF generation on a separate chip, but I'd also like it to be surface mount so I can hide it away on the 'keypad' side of the circuit board and save the other side for everything else that will be eventually packed in.
However, I'm really struggling to find anything suitable, it seems they're mostly not manufactured anymore. There are plenty of decoders, but looking through RS/Farnell/Digikey etc I can't find any generators.
The only generators I've found have to be interfaced with an MCU (e.g. MT8888CS1), and I'm happy enough using something like this (it might even provide even more flexibility). But I don't know how I'd interface my 10 number keys with it, without using whatever my central microcontroller ends up being, so if anyone has any insight here that would also be appreciated!
Thankyou!