Home made Xilinx parallel cable III not working - Page 1
Forum section: electronics / general

author: garvind25
author_rank: Regular Contributor
timestamp: July 11, 2017, 05:46:56 am
content: Hi there,My name is Arvind Gupta. I am new to this forum. I was trying to make a Xilinx parallel cable III at home. It is not working. I hope someone can help debug the issue.The document for Xilinx parallel cable III can be found here:https://www.xilinx.com/support/documentation/user_guides/xtp029.pdfAs per page 3, I made a PCB and assembled the ckt. While I was trying to program a FPGA kit with it (which has its own parallel port programmer) using iMPACT , a question came up : "There are many unknown devices being detected. Press Yes to continue or No to to stop". On selecting Yes, the software proceeded with its functioning and then hung up. There was no progress in iMPACT and I had to force-close the interface. I am attaching snapshots of the problem.Pic0: Option chosen when iMPACT opened upPic1: Description of the question which comes on choosing JTAG interfacePic2: iMPACT hanging upI am using XC3S400 FPGA kit and ISE 8.1i with it (Win XP SP2 based PC). I checked the kit by programming it with its own cable. It was working OK.So what could be the problem? Do I need to make any configuration changes in iMPACT/ ISE before I can use the XPT029 parallel port cable? I have checked the pcb layout and connections. They are OK.Awaiting your response.Thanking You,Arvind Gupta

author: alm
author_rank: Super Contributor
timestamp: July 11, 2017, 05:57:23 am
content: Does the computer you are using have a true parallel port, i.e. one connected through ISA, PCI or PCI-express? Hacks like this often do not work correctly with USB-parallel printer interfaces, which are usually made just for printers.

author: garvind25
author_rank: Regular Contributor
timestamp: July 11, 2017, 07:11:34 am
content: Thanks for your response. The kit has it own parallel port programmer. That is working. So I assume it has a true parallel port (the 25 pin pink coloured female connector is located just below the mouse PS2 connector ie. the connector is fixed on the motherboard).Regards,Arvind Gupta

author: alm
author_rank: Super Contributor
timestamp: July 11, 2017, 07:25:22 am
content: Does changing the parallel port settings in the BIOS between EPP, ECP, etc make any difference?

author: garvind25
author_rank: Regular Contributor
timestamp: July 11, 2017, 09:41:26 am
content: No it doesn't ! I have a HP-Compaq desktop. In its BIOS --> Advanced --> Printer Mode settings; there are 3 options: EPP+ECP, Output only, Bi-directional. The default set was EPP+ECP mode. I changed to the other two but no luck. In Advanced settings only, there was On board devices --> parallel port option in which I could change the settings of IRQ, DMA and address range. I tried all the 12 possible combinations but again no luck.Regards,Arvind Gupta

author: RoGeorge
author_rank: Super Contributor
timestamp: July 11, 2017, 09:57:44 am
content: The programmer from xtp029.pdf should work without any problems. I built one a few years ago, and it was working OK.Do you have a schematic for the FPGA kit? Is the built in programmer disconnected from the FPGA pins while you are using your external programmer?Since your FPGA board already has a built-in parallel programmer, I suspect there is some conflict between the on-board JTAG programmer and your external JTAG programmer, because they are both trying to drive the same JTAG pins of the FPGA.

author: garvind25
author_rank: Regular Contributor
timestamp: July 11, 2017, 10:37:24 am
content: OK... maybe I was not able to explain properly. The kit has an external parallel port cable which came along with it. That cable has a parallel port connector on one end, a box in the middle and a SIL six pin female connector on other end. On the kit, there is a SIL six pin male connector on which the cable's SIL six pin female connector gets connected.The cable which I have made has a female DB25 connector, a pcb with the circuit in the middle and a SIL six pin female connector on the other end. This connector also gets connected to the kit.So when I am testing my cable, I simply connect my cable to the PC and the kit. The programming cable which came with the kit is totally disconnected from the setup.Hope the description helps.Thanks and Regards,Arvind Gupta

author: Scrts
author_rank: Frequent Contributor
timestamp: July 11, 2017, 01:29:57 pm
content: I've also assembled that parallel port programmer a number years ago for XC9536 and it was working fine. Check your signals and the FPGA. Be sure to have correct voltage levels, e.g. FPGA might only accept 3.3V, while you're feeding 5V or so.

author: albert22
author_rank: Regular Contributor
timestamp: July 11, 2017, 01:51:52 pm
content: You can check that U1 and U2 receive the correct Vcc at pin 14 and obviosly GND at pin 7. Vcc should came from the fpga board thought diode D1, Take into account that the ICs should be type 74HC and not 74HCT for the correct operation at 3.3v.

author: garvind25
author_rank: Regular Contributor
timestamp: July 12, 2017, 04:59:33 am
content: Wonders of all wonders.... it has started working ! I checked the voltage between pins 14 and 7. It was 5.0 v. Then I before closing the system, I tried for a last time. This time the cable worked just fine ! I dont know what was wrong but ultimately it has started working. And thats all I care for. Thanks all for your efforts.Regards,Arvind Gupta

author: alm
author_rank: Super Contributor
timestamp: July 12, 2017, 05:08:16 am
content: Sounds like a bad connection. Something to check if it becomes intermittent again.