Re: [Discuss-gnuradio] Changing external reference frequency with USRP2...
On 08/16/2010 09:22 PM, Ian Holland wrote: Please disregard my last. I must have got something wrong in my testing. It now compiles, but it seems I need to use txrx_xcvr.bin instead of txrx.bin with the latest git trunk. Please correct me if this is wrong (note I have XCVR2450 as my daughterboard). This is correct. Due to the size of the code, the xcvr was split out to its own file. Also, you are right about the prescaler. Nonetheless, I still seem to get a time varying frequency offset between a transmitted and received BPSK waveform, when using the same local oscillator of 36 MHz at each end. In fact, about every million samples, this frequency offset disappears, then comes back getting larger, then smaller and disappears again about 1 million samples later. Is this expected when using a reference different to 10 MHz? When I have used two USRP2s both locked to a 10 MHz reference, I never saw this problem. No, you should not see that. It sounds like it is not locked, and I think the reason is loop bandwidth. The original setup is for a 10 MHz compare frequency, and you are using a 1 MHz compare frequency. This will mess up the loop dynamics by dividing the loop bandwidth by 10. The greatest common divisor of 100 MHz and 36 MHz is 4 MHz, so I would use that for the compare frequency. Then also increase the charge pump current to the maximum. That should bring you closer to the original loop bandwidth. Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Changing external reference frequency with USRP2...
Hi Matt Thanks so much for your help. I tried your latest suggestion, and this gets my frequency offset between Tx and Rx down to a mere 1 Hz. This is much better and should make my testing considerably simpler. Cheers Ian. -Original Message- From: Matt Ettus [mailto:m...@ettus.com] Sent: Wednesday, 18 August 2010 1:09 AM To: Ian Holland Cc: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] Changing external reference frequency with USRP2... On 08/16/2010 09:22 PM, Ian Holland wrote: Please disregard my last. I must have got something wrong in my testing. It now compiles, but it seems I need to use txrx_xcvr.bin instead of txrx.bin with the latest git trunk. Please correct me if this is wrong (note I have XCVR2450 as my daughterboard). This is correct. Due to the size of the code, the xcvr was split out to its own file. Also, you are right about the prescaler. Nonetheless, I still seem to get a time varying frequency offset between a transmitted and received BPSK waveform, when using the same local oscillator of 36 MHz at each end. In fact, about every million samples, this frequency offset disappears, then comes back getting larger, then smaller and disappears again about 1 million samples later. Is this expected when using a reference different to 10 MHz? When I have used two USRP2s both locked to a 10 MHz reference, I never saw this problem. No, you should not see that. It sounds like it is not locked, and I think the reason is loop bandwidth. The original setup is for a 10 MHz compare frequency, and you are using a 1 MHz compare frequency. This will mess up the loop dynamics by dividing the loop bandwidth by 10. The greatest common divisor of 100 MHz and 36 MHz is 4 MHz, so I would use that for the compare frequency. Then also increase the charge pump current to the maximum. That should bring you closer to the original loop bandwidth. Matt This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Changing external reference frequency with USRP2...
Thanks Matt I tried to change to get the external reference frequency to be 36 MHz, by setting B to 50 (i.e. 0x32) and R to 36 (i.e. 0x24). To do this, I modified lines 43 and 85 respectively to the following: ad9510_write_reg(0x06, 0x32); ad9510_write_reg(0x0C, 0x24); However, when I rebuilt the firmware (txrx.bin) and wrote it to the SD card, I was no longer able to see an OFDM signal I had been transmitting from another SDR at 2.4 GHz. This occurred both when I had configured the receiving SDR to lock onto the 36 MHz reference (device-config_mimo(usrp2::MC_WE_LOCK_TO_SMA)) And when I configured the receiving SDR to use its internal reference (device-config_mimo(usrp2::MC_WE_DONT_LOCK)) Have I done something wrong in my modifications? If so, can you please suggest what I am doing wrong? According to the AD9510 datasheet I believe my changes should have been correct. Best Regards Ian. -Original Message- From: Matt Ettus [mailto:m...@ettus.com] Sent: Saturday, 14 August 2010 2:15 AM To: Ian Holland Cc: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] Changing external reference frequency with USRP2... gnuradio/usrp2/firmware/lib/clocks.c, starting at line 40. You probably want to read the AD9510 datasheet to help with selecting values. Matt On 08/13/2010 12:34 AM, Ian Holland wrote: Hi I have read on the FAQ that is possible to change the external reference frequency for the USRP2 from 10 MHz to another value simply by changing one line in the firmware. However, I have as yet been unable to locate the actual source file in which I need to make this change, and what the name of this variable is. Could someone please let me know? Many Thanks Ian. This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Changing external reference frequency with USRP2...
On 08/16/2010 12:21 AM, Ian Holland wrote: Thanks Matt I tried to change to get the external reference frequency to be 36 MHz, by setting B to 50 (i.e. 0x32) and R to 36 (i.e. 0x24). To do this, I modified lines 43 and 85 respectively to the following: ad9510_write_reg(0x06, 0x32); ad9510_write_reg(0x0C, 0x24); If you set R to 36 then your compare frequency is 1 MHz. A setting of B = 50 means you are trying to lock at 50 MHz, which won't work. The crystal is at 100 MHz, so you need to use B=100. This will cause you to be way off in frequency (maybe 100 to 150 ppm). It should still function, however. However, when I rebuilt the firmware (txrx.bin) and wrote it to the SD card, I was no longer able to see an OFDM signal I had been transmitting from another SDR at 2.4 GHz. This occurred both when I had configured the receiving SDR to lock onto the 36 MHz reference (device-config_mimo(usrp2::MC_WE_LOCK_TO_SMA)) And when I configured the receiving SDR to use its internal reference (device-config_mimo(usrp2::MC_WE_DONT_LOCK)) Have I done something wrong in my modifications? If so, can you please suggest what I am doing wrong? According to the AD9510 datasheet I believe my changes should have been correct. If it doesn't work with either setting then it is likely your firmware is bad. Check to make sure you are using a good Microblaze compiler. Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Changing external reference frequency with USRP2...
Hi Matt I will try this, though given P = 2, I was under the impression the resulting VCO frequency should have been 1 MHz * P * B = 100 MHz when I have B = 50. At least, that is what the equation in the datasheet suggests. Regards Ian. -Original Message- From: Matt Ettus [mailto:m...@ettus.com] Sent: Tuesday, 17 August 2010 2:15 AM To: Ian Holland Cc: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] Changing external reference frequency with USRP2... On 08/16/2010 12:21 AM, Ian Holland wrote: Thanks Matt I tried to change to get the external reference frequency to be 36 MHz, by setting B to 50 (i.e. 0x32) and R to 36 (i.e. 0x24). To do this, I modified lines 43 and 85 respectively to the following: ad9510_write_reg(0x06, 0x32); ad9510_write_reg(0x0C, 0x24); If you set R to 36 then your compare frequency is 1 MHz. A setting of B = 50 means you are trying to lock at 50 MHz, which won't work. The crystal is at 100 MHz, so you need to use B=100. This will cause you to be way off in frequency (maybe 100 to 150 ppm). It should still function, however. However, when I rebuilt the firmware (txrx.bin) and wrote it to the SD card, I was no longer able to see an OFDM signal I had been transmitting from another SDR at 2.4 GHz. This occurred both when I had configured the receiving SDR to lock onto the 36 MHz reference (device-config_mimo(usrp2::MC_WE_LOCK_TO_SMA)) And when I configured the receiving SDR to use its internal reference (device-config_mimo(usrp2::MC_WE_DONT_LOCK)) Have I done something wrong in my modifications? If so, can you please suggest what I am doing wrong? According to the AD9510 datasheet I believe my changes should have been correct. If it doesn't work with either setting then it is likely your firmware is bad. Check to make sure you are using a good Microblaze compiler. Matt This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Changing external reference frequency with USRP2...
Hi Matt Further to below, I tried your suggestion, and still it didn't work. In fact, I have now found that the only thing that does work now is to use a pre-compiled binary that I downloaded for txrx.bin (since recompiling with the original gnuradio source code didn't work). This suggests indeed the problem is either the Microblaze tools I have (since recompiling with the original gnuradio source code didn't work) or that the version of source I had (from March 21, 2010) was corrupt to begin with. However, I even tried updating to the latest git via git pull, and tried to remake using the original clock settings. Still, it doesn't work. Hence I suspect the microblaze tools as you suggested. I got the Microblaze tools from the gnuradio website. I would have though these should work fine, but perhaps not. Is there another source you can suggest? Best Regards Ian. -Original Message- From: Ian Holland Sent: Tuesday, 17 August 2010 9:24 AM To: 'Matt Ettus' Cc: discuss-gnuradio@gnu.org Subject: RE: [Discuss-gnuradio] Changing external reference frequency with USRP2... Hi Matt I will try this, though given P = 2, I was under the impression the resulting VCO frequency should have been 1 MHz * P * B = 100 MHz when I have B = 50. At least, that is what the equation in the datasheet suggests. Regards Ian. -Original Message- From: Matt Ettus [mailto:m...@ettus.com] Sent: Tuesday, 17 August 2010 2:15 AM To: Ian Holland Cc: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] Changing external reference frequency with USRP2... On 08/16/2010 12:21 AM, Ian Holland wrote: Thanks Matt I tried to change to get the external reference frequency to be 36 MHz, by setting B to 50 (i.e. 0x32) and R to 36 (i.e. 0x24). To do this, I modified lines 43 and 85 respectively to the following: ad9510_write_reg(0x06, 0x32); ad9510_write_reg(0x0C, 0x24); If you set R to 36 then your compare frequency is 1 MHz. A setting of B = 50 means you are trying to lock at 50 MHz, which won't work. The crystal is at 100 MHz, so you need to use B=100. This will cause you to be way off in frequency (maybe 100 to 150 ppm). It should still function, however. However, when I rebuilt the firmware (txrx.bin) and wrote it to the SD card, I was no longer able to see an OFDM signal I had been transmitting from another SDR at 2.4 GHz. This occurred both when I had configured the receiving SDR to lock onto the 36 MHz reference (device-config_mimo(usrp2::MC_WE_LOCK_TO_SMA)) And when I configured the receiving SDR to use its internal reference (device-config_mimo(usrp2::MC_WE_DONT_LOCK)) Have I done something wrong in my modifications? If so, can you please suggest what I am doing wrong? According to the AD9510 datasheet I believe my changes should have been correct. If it doesn't work with either setting then it is likely your firmware is bad. Check to make sure you are using a good Microblaze compiler. Matt This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Changing external reference frequency with USRP2...
Please disregard my last. I must have got something wrong in my testing. It now compiles, but it seems I need to use txrx_xcvr.bin instead of txrx.bin with the latest git trunk. Please correct me if this is wrong (note I have XCVR2450 as my daughterboard). Nonetheless, I still seem to get a time varying frequency offset between a transmitted and received BPSK waveform, when using the same local oscillator of 36 MHz at each end. In fact, about every million samples, this frequency offset disappears, then comes back getting larger, then smaller and disappears again about 1 million samples later. Is this expected when using a reference different to 10 MHz? When I have used two USRP2s both locked to a 10 MHz reference, I never saw this problem. -Original Message- From: Ian Holland Sent: Tuesday, 17 August 2010 11:33 AM To: Ian Holland; Matt Ettus Cc: discuss-gnuradio@gnu.org Subject: RE: [Discuss-gnuradio] Changing external reference frequency with USRP2... Hi Matt Further to below, I tried your suggestion, and still it didn't work. In fact, I have now found that the only thing that does work now is to use a pre-compiled binary that I downloaded for txrx.bin (since recompiling with the original gnuradio source code didn't work). This suggests indeed the problem is either the Microblaze tools I have (since recompiling with the original gnuradio source code didn't work) or that the version of source I had (from March 21, 2010) was corrupt to begin with. However, I even tried updating to the latest git via git pull, and tried to remake using the original clock settings. Still, it doesn't work. Hence I suspect the microblaze tools as you suggested. I got the Microblaze tools from the gnuradio website. I would have though these should work fine, but perhaps not. Is there another source you can suggest? Best Regards Ian. -Original Message- From: Ian Holland Sent: Tuesday, 17 August 2010 9:24 AM To: 'Matt Ettus' Cc: discuss-gnuradio@gnu.org Subject: RE: [Discuss-gnuradio] Changing external reference frequency with USRP2... Hi Matt I will try this, though given P = 2, I was under the impression the resulting VCO frequency should have been 1 MHz * P * B = 100 MHz when I have B = 50. At least, that is what the equation in the datasheet suggests. Regards Ian. -Original Message- From: Matt Ettus [mailto:m...@ettus.com] Sent: Tuesday, 17 August 2010 2:15 AM To: Ian Holland Cc: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] Changing external reference frequency with USRP2... On 08/16/2010 12:21 AM, Ian Holland wrote: Thanks Matt I tried to change to get the external reference frequency to be 36 MHz, by setting B to 50 (i.e. 0x32) and R to 36 (i.e. 0x24). To do this, I modified lines 43 and 85 respectively to the following: ad9510_write_reg(0x06, 0x32); ad9510_write_reg(0x0C, 0x24); If you set R to 36 then your compare frequency is 1 MHz. A setting of B = 50 means you are trying to lock at 50 MHz, which won't work. The crystal is at 100 MHz, so you need to use B=100. This will cause you to be way off in frequency (maybe 100 to 150 ppm). It should still function, however. However, when I rebuilt the firmware (txrx.bin) and wrote it to the SD card, I was no longer able to see an OFDM signal I had been transmitting from another SDR at 2.4 GHz. This occurred both when I had configured the receiving SDR to lock onto the 36 MHz reference (device-config_mimo(usrp2::MC_WE_LOCK_TO_SMA)) And when I configured the receiving SDR to use its internal reference (device-config_mimo(usrp2::MC_WE_DONT_LOCK)) Have I done something wrong in my modifications? If so, can you please suggest what I am doing wrong? According to the AD9510 datasheet I believe my changes should have been correct. If it doesn't work with either setting then it is likely your firmware is bad. Check to make sure you are using a good Microblaze compiler. Matt This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Changing external reference frequency with USRP2...
Hi I have read on the FAQ that is possible to change the external reference frequency for the USRP2 from 10 MHz to another value simply by changing one line in the firmware. However, I have as yet been unable to locate the actual source file in which I need to make this change, and what the name of this variable is. Could someone please let me know? Many Thanks Ian. This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
