Phone Line Sim Schematic (and some issues)
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- เผยแพร่เมื่อ 29 ก.ย. 2024
- Here's the schematic of the various phone line related modules I've been working with on the breadboard including the KS0835F SLIC, MT8870 DTMF Decoder, ESP8266, PCF8574 GPIO expander, and misc analog and digital glue circuitry.
Project on github: github.com/Gad...
DTMF Decoder project: github.com/Gad...
KS0835F phone line module: github.com/Gad...
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I've watched all of your "episodes" in making this and I love it!
I originally came to see how I could make an "old" phone tester, testing pulse dial or DTMF to BCD so to display the dialed number on a 7 segment display; .also using the SLIC just to provide ringing current.
Now I may make a phone to phone demo board of my own! You sir, have expanded my horizon; thank you so much.
Incidently in the UK we call the Central Office the Exchange.
Also watching earlier " episodes" it struck me that perhaps you could hive off the service signal generation to another processor and just call the tones as required...
I’m currently ordering more parts to try some more things out including making a sort of expansion switching matrix where a bunch of exchanges can all plug-in and it will have its own way of routing calls between several different nodes, so there could be multiple separate calls in place or even party lines with more than two on the same circuit. I’ve been working on it more than five years at this point so the ideas keep coming.
Going over to the esp32 is a good idea as you can keep your phone code in core1 and leave core0 to keep Wi-Fi happy
I was even thinking about having the audio stuff handled by one core so that it wouldn’t worry about hiccups from other code slowing it down but if I could also get Wi-Fi working reliably that would be good because that was my original plan to talk between nodes instead of RS 485 but ESP 8266 made that impossible. So I definitely think I’ll be doing another hardware revision at some point.
Cool!
Not to be too much of a party pooper it would be nice if circuit flow runs from left to right. You i2c to the gpio expander reverses the flow direction. Must my ocd playing up again.
usually I try to go left to right especially with connectors that are input versus output but sometimes just getting it slapped together is good enough especially if it’s only temporary, and also it depends on things like those circuit blocks with the pins on the right side instead of the left, I would have to have redrawn that in order to get the GPIO expander flowing in the right direction so it just got wired up however it needed to get it done. The ESP 32 version will probably be more aesthetically compliant
@@gadgetsideload Did you try flipping the component hor and vert to change the input to the left.
I had to work on a design for relay logic and the circuit was drawn with the relay to look like the component pin out. They had not separated the coil from the contacts. So trying to follow a diagram that the connections when from left to right then back and then round in circles was near impossible. in the end in my log book i did a quick drawing with coils, relay contacts as individual parts, working left to right and had it sussed in a few hrs. but then had to convert the mod back in to the mess.
Never understand the requirement to keep a chip as one part in a schematic.
Don't get me started on the folks who draw the entire drawing as chips and net lists. so you have to hunt around to find where the signals go. It's no wonder that when they make the boards there are connections missing as you can't see the flow on the schematic.
Time for bed now, my headaches 🙂
I can flip the components to get the pins on the other sides, but I'm not sure if I can do the same with the hierarchy schematic blocks (probably can, didn't think to try).
The thing I hate most is schematics where the symbol for a chip is drawn as a rectangle with pins to look like the physical chip, so I have to go find the datasheet to see which pins are gate inputs/outputs or op amp in/out.
My head hurts now too, I just finished adding more software features/states to the system and I'm about to try using one node to dial the other node with a phone number. But first I get to go shovel 20cm of snow!
@@gadgetsideload Wish we got snow, we just get cold and damp in winter and warm and damp in summer. 🙂
With hierarchy block can't you just move the connectors around, i sure you can.
not sure if you can do it top level or you have ot open the sheet.
I haven’t used it very often in this schematic tool so I keep forgetting what’s possible and how to do it, and I’m just rushed. On the bright side I just finished some testing with two of these designs successfully letting one phone call the other and establish a connection so now I have to get the camera out before the whole thing falls apart.