I2C protocol analog control of a TV tuner

[amr_electron]

I²C, analoge control .

I have a tv tuner detached from a PCI card . It's based on I²C protocol
How can i control it in an anloge way, which means :
How can i apply the tunning voltage & how can i select the desired band ?

Best Regards .

 

[IanP]

Re: I²C, analoge control .

This will be a very difficult task, if almost impossible..
Probably slightly easier would be to find out what commands are used to control this tuner and "take over" control from the I2C bus using microcontroller with I2C interface..

 

[amr_electron]

Re: I²C, analoge control .

Thanks IanP,
but i cann't find a schematic for a separated interface with a pic which could do the channels search & band selecting without the computer .
regards.

 

[IanP]

Re: I²C, analoge control .

Could you describe your tuner: usually this will be shielded box with 10 (or so) pins/wires on its long side and RF-input on the short side.
Maybe you will be able to identify control pins be measuring dc-voltages.
Usefull thing would be extention cable for PCI bus (I am not sure if you can by one) so you can have this card out of motherboard slot.

 

[firemaker]

Re: I²C, analoge control .

HI all,
i'm also trying to do the same stuff, as it's too difficult for me to write my
own software for the pic in addition to understanding the I2C system .
i found an I2C interface which is used to convert the old tv sets without
remote control to remote controlled TVs . it has it's remote control
and 24C04 eeprom & it can store up to 99 channels and it doesn't require
lots of connections .
attached is a schematic of the interface, i need to know if the tuner could be
controlled in this way or not & where to connect the SCL & SDA of the tuner .
thanx.

 

[amr_electron]

Re: I²C, analoge control .

i'm so grateful IanP,
the tuner was from a Hauppauge card, with direct CVBS/Audio output .
i will open the can & look for further informations as i cann't
measure any voltages because it's already taken out .

regards.

 

[amr_electron]

Re: I²C, analoge control .

the tuner is controlled by the TSA5522T . it's 1.4 GHz I2C-bus controlled synthesizer .

 

[IanP]

Re: I²C, analoge control .

Now it should be reasonably easy to raplace signals P0, P1 and P2 with switches (L=0V, H=5V) to select VHF1, VHF2 or UHF.
You will also need a voltage source (33Vdc) for Vtune - use 100kΩ potentiometer for tunning, and that should be it..

 

[amr_electron]

Re: I²C, analoge control .

Thanks IanP,
i will tryout this solution & let you know .
regards.

 

[amr_electron]

Re: I²C, analoge control .

It works, but i had to disconnect the loop filter which is connected between
the Vtune & pin 10 of the synthesizer (this pin is identified as CP in the datasheet) , by doing this varying the frequency is done by changing the Vtune .
thanks IanP .