MachXO2 FTDI USB cable only for programming? - Page 1
Forum section: electronics / general

author: David Kenny
author_rank: Newbie
timestamp: September 03, 2014, 03:40:48 am
content: Hello all, first time poster on EEVBlog here.I just purchased the MachXO2 breakout board after viewing Mike's video on driving LED matrix displays. I've only had it a few days and am having much fun playing with it so far.All the documentation I have read about it only talks about using the USB cable for programming. I am thinking, with some modifications, it should be able to be switched between programming and uart communications with a project running on the FPGA. I know I can get another FTDI USB to serial cable to use with a soft uart in the FPGA, but I would rather use the one on the breakout board.Does anyone have any thoughts on this? I'm new here, but I'm not looking for someone to do this for me. Just looking for advice.@Mike: Your video also touched on uart communications. How was yours setup?David

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: September 04, 2014, 01:57:23 am
content: Older threads on same subject:harvs thread:https://www.eevblog.com/forum/microcontrollers/machxo2280-board-serial-over-jtag/hlavac thread:https://www.eevblog.com/forum/microcontrollers/communication-over-jtag/

author: jeremy
author_rank: Super Contributor
timestamp: September 04, 2014, 04:33:17 am
content: Not sure why everyone is recommending soldering wires? Channel B is already connected to the MachXO2 as a uart->usb converter according to the datasheet:http://www.latticesemi.com/~/media/Documents/UserManuals/MQ/MachXO2BreakoutBoardEvaluationKitUsersGuide.pdf

author: Torrentula
author_rank: Regular Contributor
timestamp: September 04, 2014, 08:14:35 am
content: Jeremy I think the links posted are referring to the Lattice MachXO series breakout board for the MachXO 2280 CPLD.I do own that board and can confirm that the FT2232 is not connected to the CPLD as a USB UART converter.Which board do you use? The MachXO2 breakout might have the FT2232 connected to the FPGA other than just for JTAG.

author: abyrvalg
author_rank: Frequent Contributor
timestamp: September 04, 2014, 08:59:43 am
content: A side note: you don't need to stick to UART mode with it's async sampling, FTDI works as SPI master also - more FPGA-friendly.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 04, 2014, 09:22:35 am
content: The second port on the 2232 is available - from memory I think you need to fit some resistors to connect it. It's annoying they didn't put the basic UART signals on a pin header.

author: David Kenny
author_rank: Newbie
timestamp: September 04, 2014, 09:39:20 am
content: Torrentula, the links posted by chickenHeadKnob are indeed for older boards. Same situation though.Jeremy, the User Guide you posted was the correct one for my board (has the 7000HE chip as it shows in the picture). It mentions the USB Mini-B socket that connects to the FT2232H. The FT2232H is connected to the FPGA using the JTAG interface. No mention of Channel B.The attached picture is from the guide Jeremy linked to in his post. It shows an 8 pin chip on the left side of the FT2232H, between it an the 7000HE. You can see the traces going to pins 61-63 on the FT2232H. That is the EEPROM configuration chip for the FT2232H. I was going to say that I believe you would need to reprogram it to enable and configure Channel B on the FT2232H. But Mike posted that channel B is available while I was composing this post.Mike, I like that news! Can I assume you are talking about using resistors to lower the 5V the FT2232H is using (supplied by the USB cable) to 3.3V for the FPGA?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 04, 2014, 09:49:58 am
content: R14-20 on the underside, also shown on the schematic.

author: jeremy
author_rank: Super Contributor
timestamp: September 04, 2014, 09:54:02 am
content: Hi David,Ignore the datasheet fluff and go to the schematic at the end of the document. It is on there. I will continuity check my board when I get home as well.edit: yes, as long as you fit the resistors (ie wires for me) then it works fine.

author: David Kenny
author_rank: Newbie
timestamp: September 04, 2014, 10:23:13 am
content: Thanks Mike and Jeremy, I see it now. Although it was searchable, my search terms didn't find it. Sigh...Looks like the traces and smd pads are all there, just need to add the smd zero-Ohm resistors (jumpers). Sweet!