Hi. First let me explain what I am trying to accomplish. I want a device that will block calls or keep the phone from ringing. Maybe a button for when a caller calls and you press it then it will never let that number ring the phone again. Now I read a similar problem awhile back in a post here and someone, can't remember who at this time, built a device that would do this pretty much with a few added features I think. Now, I will go that route eventually but first I just wanted to experiment with an old Caller ID I found lying around my house. I thought maybe I could get this done relatively easy.
My plan was to open it up and find the decoder chip and see if I could find the datasheet for it. I did and it's a CML fx602. I then located the RXD pin and was going to hook my logic analyzer (LogicPORT USB) up to it and read the data. The datasheet for the fx602 said it has two modes, where a MCU could clock out the data for situations where a UART was not wanted or available, or keeping the RXCK pin high, you could use a UART. So the reason I wanted to examine this before just pluging my MCU up to it and intercepting the data was to make sure how the data was being handled. Now everytime I hook the probes up to the fx602, one to the RXD and the ground to the Vss of the chip, it somehow shorts out or something because the phone connects and stays connected until I disconnect the ground probe. In other words, it won't let me call the phone so I can get the caller ID info to it.
I do not have a regular phone line, I have VoIP with Vonage. I really thought this would be easy, just open the caller ID up find the RX pin, intercept the caller ID data sending it to my MCU where my program would examine it and compare to data stored in a memory chip, depending on successful compare it would trigger relay to disconnect line. Something like that. There was already a relay on this caller ID and everything for call waiting muting during the data transfer.
So what the heck am I doing wrong? I am an amateur so I am probably doing something dumb.
I also tried using my oscilloscope and it does the same thing. Now when I unplug the caller ID from the wall it doesn't do it anymore. Only problem then is the caller ID doesn't get the caller info unless it's plugged in, it only lets you see time and past calls on battery power. I guess I could get a 9 V battery and use that to power the Caller ID instead of the 9V wall wart. When I read the voltages across the pins of the chip with a DMM they are all 4.8 V or 0 V. So I dunno..?
Any help would be appreciated.
Thanks,
Michael Walden
My plan was to open it up and find the decoder chip and see if I could find the datasheet for it. I did and it's a CML fx602. I then located the RXD pin and was going to hook my logic analyzer (LogicPORT USB) up to it and read the data. The datasheet for the fx602 said it has two modes, where a MCU could clock out the data for situations where a UART was not wanted or available, or keeping the RXCK pin high, you could use a UART. So the reason I wanted to examine this before just pluging my MCU up to it and intercepting the data was to make sure how the data was being handled. Now everytime I hook the probes up to the fx602, one to the RXD and the ground to the Vss of the chip, it somehow shorts out or something because the phone connects and stays connected until I disconnect the ground probe. In other words, it won't let me call the phone so I can get the caller ID info to it.
I do not have a regular phone line, I have VoIP with Vonage. I really thought this would be easy, just open the caller ID up find the RX pin, intercept the caller ID data sending it to my MCU where my program would examine it and compare to data stored in a memory chip, depending on successful compare it would trigger relay to disconnect line. Something like that. There was already a relay on this caller ID and everything for call waiting muting during the data transfer.
So what the heck am I doing wrong? I am an amateur so I am probably doing something dumb.
I also tried using my oscilloscope and it does the same thing. Now when I unplug the caller ID from the wall it doesn't do it anymore. Only problem then is the caller ID doesn't get the caller info unless it's plugged in, it only lets you see time and past calls on battery power. I guess I could get a 9 V battery and use that to power the Caller ID instead of the 9V wall wart. When I read the voltages across the pins of the chip with a DMM they are all 4.8 V or 0 V. So I dunno..?
Any help would be appreciated.
Thanks,
Michael Walden