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FW: exchanging data trough the Ethernet card.

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FW: exchanging data trough the Ethernet card. by Unknown on Jun 24, 2008			Not available!
Hi Andrea, Your question looks familier to me as I had the same issue some time back when trying to communicate with a PIC Micro from PC using Ethernet. I really wanted to drop all the TCP / IP stack stuff and get the ethernet frame across. But from what I learnt and experienced, you may need to do lot of tweaks to by-pass the TCP / IP stack of the operating system first. Simply, what gets passed to an application running on top of a generic OS with generic drivers, is the payload of either TCP or UDP packet. Hence, you may first have to write your own sockets / drivers to get raw data from the NIC of your PC. Again the MAC and PHY of the NIC comes embedded inside the controller. (Jeepers! you can't strip them off). So the maximum depth you can go to, is the MAC layer, provided that you do all these tweaks. For the same, you may have to have the stack upto the MAC layer implemented in the FPGA as well.... Have a nice day!! Thaya. ----- Original Message ----- From: "NewsGroup" <<A HREF="http://www.opencores.org/mailman/listinfo/ethmac">nbase at n...</A>> To: <<A HREF="http://www.opencores.org/mailman/listinfo/ethmac">ethmac at o...</A>> Date: Thu, 24 Aug 2000 09:33:20 -0700 Subject: RE: [ethmac] FW: exchanging data trough the Ethernet card. [q] 24-Aug-00 Hi, Both question depend on your card. Most likely the ful duplex can be change by software as you most likely have a register in the card that you write to it telling the card wether to work in full duplex or half duplex. now days I belive everyone make the Ethernet interface to work in both mode just as all new 100 are actually 10/100 simple because it is almost the same effort. If I understand your second question you would like to send short packet with are shorter than what the Ethernet standart allow. in general this can sure be done just as you can shronk the preamble in the "network" you will have the "big" question is will your card support it !. many card will filter all packet that are short than 64 and simple reject them and rais an error flag, and on the other direction in many cases the card will add padding to get the minimum size. so if I understand right what you want to do , you will need to find a card that will forward to the cpu even fragment packets as well as "agree" to send short packet to the line. and if you don't find such card I guess you will have to design one. have a nice day Illan -----Original Message----- From: <A HREF="http://www.opencores.org/mailman/listinfo/ethmac">owner-ethmac at o...</A> [/q] [/cgi-bin/post.cgi?cmd=new&to=owner-ethmac%20at%20opencores%20dot%20org&msg=/ml-archive/archives/ethmac/0008/msg00010.shtml [q] Behalf Of Andrea Aizza Sent: Wednesday, August 23, 2000 8:13 AM To: Jean-FranÃ§ois Larin Cc: <A HREF="http://www.opencores.org/mailman/listinfo/ethmac">ethmac at o...</A> Subject: Re: [ethmac] FW: exchanging data trough the Ethernet card. Dear Jean-Francois, thank you for your help. I have some further comments: On 23-Aug-00 Jean-FranÃ§ois Larin wrote: [q]> Dear OPENCORE friends, > > I have never worked with Ethernet protocol but I need [/q] about 15Mbps from an [q]> FPGA > device and a PC. One idea I thought today to implement a [/q] `null modem` based [q]> connection from the PC to the device (just two devices - [/q] no hubs or friends) [q]> I > have just 2 questions: > > 1) Assuming they claim 10/100Mbps on those Eth cards, can [/q] you really reach [q]> those speeds? [/q] > > Ethernet works in half duplex and in full duplex. If you are [/q] working in half [q]> duplex, then only one device can speak on the wire at the same [/q] time, so you [q]> get > 10/100 Mbps. But when 2 device start to transmit on the wire [/q] on the same [q]> time, > there is a collision and both have to retry. If there is [/q] litte traffic, [q]> there is > little collisions. When more traffic gets in you get more [/q] collision. I've [q]> heard > that you reach at peak at about 30% of utilisation (3/30 Mbps) [/q] If you try to [q]> use > more bandwidth, you get too much collision and the actual [/q] bandwidth decrease. [q]> > But since you only use 2 devices, you can use full duplex (if [/q] you use a [q]> unshielded > twistet pairs (similar to telephone jack in north america). [/q] Full duplex is [q]> not > supporter on co-axial cable (afaik). Then you get a real [/q] 100Mbs. [q]> [/q] I understood that, is the full duplex mode something you set by software? In fact hat i have to do is a hardware part and a software one. [q]> In fact, you never get 100 percent of the 100Mbs. Every [/q] packet has a 12 [q]> bytes of > addresses, 2 bytes for type and 4 bytes for CRC. The total [/q] packet lenght [q]> must be > between 64 bytes or 1518 bytes. between each packet, there is [/q] some overhead [q]> equivalent to 20 bytes (12 for inter-packet gap and 8 for [/q] pre-amble). So if [q]> you use > large packets (because you actually have lot of information to [/q] send), the [q]> overhead > (12+2+4+20) is negligible compared to 1518 bytes, so you get [/q] almost 100Mbs of [q]> true > bandwidth. If you use full duplex, you get all this bandwith [/q] 'guaranteed' [q]> because > there is no collision. that is as far as Ethernet is [/q] concerned. You Eth [q]> Card must > be of good design. Maybe the cheap (old) cards use I/O access [/q] to transfer [q]> the > packets. Then your CPU is going to be the limitations. [/q] no problem with the card, we can buy a new one if our is not enought good. What I do not understood here is: if I attach the ethernet rj45 cable to my FPGA (just thos etwo devices) and I write some HDL code in such a way that it sends on that serial ethernet link a packet of lets say 1000 bytes, well formatted (using the right system info - header, addresses..., and obviuosly the right frequency) is it there the way to read it by writing some software on the PC? And on the other way, if I write some software, can I send just a packet on the ethernet in such a way that I can read it in my FPGA? I think this is what I need to do! Thank you again for your help. Have a great week, Andrea. [q]> > Note also that Ethernet is not like a null modem. You have to [/q] send data in [q]> packets. > You can't just send a single caracter on the wire. > > good luck > > > -- > > ********************************************************** > Jean-Francois Larin ing. stag. > FPGA design > Network Products Group > Matrox Electronic Systems > 1055 St. Regis Blvd. > Dorval, Quebec, Canada > H9P 2T4 > Tel:(514)685-7230 ext. 2041 > Fax:(514)822-6272 > E-Mail: <A HREF="http://www.opencores.org/mailman/listinfo/ethmac">JeanFrancois.Larin at m...</A> > ******************************************************** > [/q] ---------------------------------------- Andrea AIZZA ---------------------------------------- Swiss Federal Institute of Technology Department of Electrical Engineering Integrated Systems Center (LSI) EPFL-DE-LSI Office: ELB-137 Ecublens, CH-1015 Lausanne (CH) tel. +41 21 693 69 73 fax. +41 21 693 46 63 email <A HREF="http://www.opencores.org/mailman/listinfo/ethmac">Andrea.Aizza at e...</A> <A HREF="http://lsiwww.epfl.ch/">http://lsiwww.epfl.ch/</A> ---------------------------------------- [/q] Hi Andrea, Your question looks familier to me as I had the same issue some time back when trying to communicate with a PIC Micro from PC using Ethernet. I really wanted to drop all the TCP / IP stack stuff and get the ethernet frame across. But from what I learnt and experienced, you may need to do lot of tweaks to by-pass the TCP / IP stack of the operating system first. Simply, what gets passed to an application running on top of a generic OS with generic drivers, is the payload of either TCP or UDP packet. Hence, you may first have to write your own sockets / drivers to get raw data from the NIC of your PC. Again the MAC and PHY of the NIC comes embedded inside the controller. (Jeepers! you can't strip them off). So the maximum depth you can go to, is the MAC layer, provided that you do all these tweaks. For the same, you may have to have the stack upto the MAC layer implemented in the FPGA as well.... Have a nice day!! Thaya. ----- Original Message ----- From: "NewsGroup" nbase at n...> To: ethmac at o...> Date: Thu, 24 Aug 2000 09:33:20 -0700 Subject: RE: [ethmac] FW: exchanging data trough the Ethernet card. 24-Aug-00 Hi, Both question depend on your card. Most likely the ful duplex can be change by software as you most likely have a register in the card that you write to it telling the card wether to work in full duplex or half duplex. now days I belive everyone make the Ethernet interface to work in both mode just as all new 100 are actually 10/100 simple because it is almost the same effort. If I understand your second question you would like to send short packet with are shorter than what the Ethernet standart allow. in general this can sure be done just as you can shronk the preamble in the "network" you will have the "big" question is will your card support it !. many card will filter all packet that are short than 64 and simple reject them and rais an error flag, and on the other direction in many cases the card will add padding to get the minimum size. so if I understand right what you want to do , you will need to find a card that will forward to the cpu even fragment packets as well as "agree" to send short packet to the line. and if you don't find such card I guess you will have to design one. have a nice day Illan -----Original Message----- From: owner-ethmac at o... [/cgi-bin/post.cgi?cmd=new&to=owner-ethmac%20at%20opencores%20dot%20org&msg=/ml-archive/archives/ethmac/0008/msg00010.shtml Behalf Of Andrea Aizza Sent: Wednesday, August 23, 2000 8:13 AM To: Jean-FranÃ§ois Larin Cc: ethmac at o... Subject: Re: [ethmac] FW: exchanging data trough the Ethernet card. Dear Jean-Francois, thank you for your help. I have some further comments: On 23-Aug-00 Jean-FranÃ§ois Larin wrote: > Dear OPENCORE friends, > > I have never worked with Ethernet protocol but I need about 15Mbps from an > FPGA > device and a PC. One idea I thought today to implement a `null modem` based > connection from the PC to the device (just two devices - no hubs or friends) > I > have just 2 questions: > > 1) Assuming they claim 10/100Mbps on those Eth cards, can you really reach > those speeds? > > Ethernet works in half duplex and in full duplex. If you are working in half > duplex, then only one device can speak on the wire at the same time, so you > get > 10/100 Mbps. But when 2 device start to transmit on the wire on the same > time, > there is a collision and both have to retry. If there is litte traffic, > there is > little collisions. When more traffic gets in you get more collision. I've > heard > that you reach at peak at about 30% of utilisation (3/30 Mbps) If you try to > use > more bandwidth, you get too much collision and the actual bandwidth decrease. > > But since you only use 2 devices, you can use full duplex (if you use a > unshielded > twistet pairs (similar to telephone jack in north america). Full duplex is > not > supporter on co-axial cable (afaik). Then you get a real 100Mbs. > I understood that, is the full duplex mode something you set by software? In fact hat i have to do is a hardware part and a software one. > In fact, you never get 100 percent of the 100Mbs. Every packet has a 12 > bytes of > addresses, 2 bytes for type and 4 bytes for CRC. The total packet lenght > must be > between 64 bytes or 1518 bytes. between each packet, there is some overhead > equivalent to 20 bytes (12 for inter-packet gap and 8 for pre-amble). So if > you use > large packets (because you actually have lot of information to send), the > overhead > (12+2+4+20) is negligible compared to 1518 bytes, so you get almost 100Mbs of > true > bandwidth. If you use full duplex, you get all this bandwith 'guaranteed' > because > there is no collision. that is as far as Ethernet is concerned. You Eth > Card must > be of good design. Maybe the cheap (old) cards use I/O access to transfer > the > packets. Then your CPU is going to be the limitations. no problem with the card, we can buy a new one if our is not enought good. What I do not understood here is: if I attach the ethernet rj45 cable to my FPGA (just thos etwo devices) and I write some HDL code in such a way that it sends on that serial ethernet link a packet of lets say 1000 bytes, well formatted (using the right system info - header, addresses..., and obviuosly the right frequency) is it there the way to read it by writing some software on the PC? And on the other way, if I write some software, can I send just a packet on the ethernet in such a way that I can read it in my FPGA? I think this is what I need to do! Thank you again for your help. Have a great week, Andrea. > > Note also that Ethernet is not like a null modem. You have to send data in > packets. > You can't just send a single caracter on the wire. > > good luck > > > -- > > ******************************************************** > Jean-Francois Larin ing. stag. > FPGA design > Network Products Group > Matrox Electronic Systems > 1055 St. Regis Blvd. > Dorval, Quebec, Canada > H9P 2T4 > Tel:(514)685-7230 ext. 2041 > Fax:(514)822-6272 > E-Mail: JeanFrancois.Larin at m... > ********************************************************** > ---------------------------------------- Andrea AIZZA ---------------------------------------- Swiss Federal Institute of Technology Department of Electrical Engineering Integrated Systems Center (LSI) EPFL-DE-LSI Office: ELB-137 Ecublens, CH-1015 Lausanne (CH) tel. +41 21 693 69 73 fax. +41 21 693 46 63 email Andrea.Aizza at e... http://lsiwww.epfl.ch/ ----------------------------------------

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