Re: [Discuss-gnuradio] Inquiry about automatic gain control
On Mon, Dec 1, 2008 at 10:53 PM, [EMAIL PROTECTED] wrote: I am trying to achieve a goal of controlling the AGC, please help. Here is what I have so far, for the automatic gain control (AGC): I have found in the module adc_interface (which is in fpga\sdr_lib\adc_interface) a comment about level sensing for the AGC. I am assuming the module rssi and module adc_interface is where the AGC is controlled? If not where do I go about turning on or off the AGC. The rssi is used to sense the signal strength in the fpga and that is feedback to the ADC which controls the AGC, is that correct? I don't believe there is any AGC actually going on at all. Please see here: http://gnuradio.org/trac/ticket/66 After I know how to turn on and off the AGC, how do I adjust the gain of the amplifier? You need to familiarize yourself with the gain settings of the different daughterboards and how their gains are controlled. The Python db code is probably a good place to start looking. If I wanted to make a block diagram, or refer to a schematic that involves the AGC, where should I start? Is the AGC located before the ADC, and the ADC is contained in the fpga, right? The ADC is an external chip. The data feeds into the FPGA where it is then processed. Thank you so much for your time and help, Good luck. Brian ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Inquiry about automatic gain control
Brian, If you refer to the usrp\fpga\sdr_lib\adc_interface.v this is a comment stating: \\level sensing for AGC on line 67 of the verilog code file. I have read on the wiki that AGC can be implemented by moving resistors around, can you elaborate on this: which resistors, and on what board? I am assuming that there is some sort of feedback loop for the FPGA to an amplifier which uses the RSSI, is there not one? Thanks for your time and help. -Benjamin Dannan Quoting Brian Padalino [EMAIL PROTECTED]: On Mon, Dec 1, 2008 at 10:53 PM, [EMAIL PROTECTED] wrote: I am trying to achieve a goal of controlling the AGC, please help. Here is what I have so far, for the automatic gain control (AGC): I have found in the module adc_interface (which is in fpga\sdr_lib\adc_interface) a comment about level sensing for the AGC. I am assuming the module rssi and module adc_interface is where the AGC is controlled? If not where do I go about turning on or off the AGC. The rssi is used to sense the signal strength in the fpga and that is feedback to the ADC which controls the AGC, is that correct? I don't believe there is any AGC actually going on at all. Please see here: http://gnuradio.org/trac/ticket/66 After I know how to turn on and off the AGC, how do I adjust the gain of the amplifier? You need to familiarize yourself with the gain settings of the different daughterboards and how their gains are controlled. The Python db code is probably a good place to start looking. If I wanted to make a block diagram, or refer to a schematic that involves the AGC, where should I start? Is the AGC located before the ADC, and the ADC is contained in the fpga, right? The ADC is an external chip. The data feeds into the FPGA where it is then processed. Thank you so much for your time and help, Good luck. Brian ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Inquiry about automatic gain control
Brian, Can AGC be implemented in code, on the verilog side using the FPGA? Thanks -Benjamin uoting Brian Padalino [EMAIL PROTECTED]: On Mon, Dec 1, 2008 at 10:53 PM, [EMAIL PROTECTED] wrote: I am trying to achieve a goal of controlling the AGC, please help. Here is what I have so far, for the automatic gain control (AGC): I have found in the module adc_interface (which is in fpga\sdr_lib\adc_interface) a comment about level sensing for the AGC. I am assuming the module rssi and module adc_interface is where the AGC is controlled? If not where do I go about turning on or off the AGC. The rssi is used to sense the signal strength in the fpga and that is feedback to the ADC which controls the AGC, is that correct? I don't believe there is any AGC actually going on at all. Please see here: http://gnuradio.org/trac/ticket/66 After I know how to turn on and off the AGC, how do I adjust the gain of the amplifier? You need to familiarize yourself with the gain settings of the different daughterboards and how their gains are controlled. The Python db code is probably a good place to start looking. If I wanted to make a block diagram, or refer to a schematic that involves the AGC, where should I start? Is the AGC located before the ADC, and the ADC is contained in the fpga, right? The ADC is an external chip. The data feeds into the FPGA where it is then processed. Thank you so much for your time and help, Good luck. Brian ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Inquiry about automatic gain control
[EMAIL PROTECTED] wrote: Brian, If you refer to the usrp\fpga\sdr_lib\adc_interface.v this is a comment stating: \\level sensing for AGC on line 67 of the verilog code file. I have read on the wiki that AGC can be implemented by moving resistors around, can you elaborate on this: which resistors, and on what board? I am assuming that there is some sort of feedback loop for the FPGA to an amplifier which uses the RSSI, is there not one? By moving some resistors around you can implement a completely analog AGC function on the RFX900, 1200, 1800, and 2400. It will not work on the RFX400. In general, there are many ways you can implement AGC, depending on where you implement the RSSI sensing and the control functions. Nothing has been done to prevent you from doing any of these, but it is an exercise left to the user, as they say. Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Inquiry about automatic gain control
Matt, So it is possible to be implemented in code on the verilog side? If so, do you have any suggestions on where to start? Thanks for your help Regards, Benjamin Dannan Quoting Matt Ettus [EMAIL PROTECTED]: [EMAIL PROTECTED] wrote: Brian, If you refer to the usrp\fpga\sdr_lib\adc_interface.v this is a comment stating: \\level sensing for AGC on line 67 of the verilog code file. I have read on the wiki that AGC can be implemented by moving resistors around, can you elaborate on this: which resistors, and on what board? I am assuming that there is some sort of feedback loop for the FPGA to an amplifier which uses the RSSI, is there not one? By moving some resistors around you can implement a completely analog AGC function on the RFX900, 1200, 1800, and 2400. It will not work on the RFX400. In general, there are many ways you can implement AGC, depending on where you implement the RSSI sensing and the control functions. Nothing has been done to prevent you from doing any of these, but it is an exercise left to the user, as they say. Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
