USB to I2C Master Reference Designs? - Page 1
Forum section: electronics / projects

author: bhj99
author_rank: Contributor
timestamp: May 03, 2023, 11:09:42 pm
content: Hi all! Does nayone know of any reference design that can support USB to I2C as a master? I am trying to provide an I2C interface used for communicating to an SFP+ transceiver (would as as the slave device) in my project. I am considering using the FTDI FT232HL chip to handle the interface conversion, but I couldn't find a good reference schematic pertaining to I2C. If there are other devices for this application, I would certainly like to know as well. Any help is appreciated!

author: coromonadalix
author_rank: Super Contributor
timestamp: May 03, 2023, 11:27:33 pm
content: https://ftdichip.com/wp-content/uploads/2021/08/AN_255_USB-to-I2C-Example-using-the-FT232H-and-FT201X-devices.pdfhttps://ftdichip.com/wp-content/uploads/2020/07/AN_355_FT232H-MPSSE-Example-I2C-Master-Interface-with-Visual-Basic.pdfhttps://ftdichip.com/Documents/AppNotes/AN_113_FTDI_Hi_Speed_USB_To_I2C_Example.pdfhttps://www.adafruit.com/product/2264https://learn.adafruit.com/adafruit-ft232h-with-spi-and-i2c-libraries/i2c-deviceshttps://krinkinmu.github.io/2020/09/06/ftdi-i2c.html

author: bhj99
author_rank: Contributor
timestamp: May 04, 2023, 12:11:06 am
content: Thank you, I've found these documents too, but I was hoping to find a full circuit schematic with the FT232H part that implements USC to I2C. Most of these are software/programming implementations, and I'm interested on how to hook up the device. The one that comes close is the AN_113 document.Perhaps you help me interpet which ADBUS pins correspond to I2C_SDA and I2C_CLK? Page 9 of the FT232H datasheet below isn't real clear to me...https://ftdichip.com/wp-content/uploads/2020/07/DS_FT232H.pdf

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 04, 2023, 05:20:44 am
content: Take the schematics form AN_113, match the pin names (ADBUS0, etc) to FT232.The only trick on the FTDI chip is that there are independent data in / data out pins, which connected together to form the SDA line.

author: fchk
author_rank: Frequent Contributor
timestamp: May 04, 2023, 10:05:13 am
content: Quote from: bhj99 on May 03, 2023, 11:09:42 pmMicrochip MCP2221A.https://www.microchip.com/en-us/product/MCP2221ABreakout Board:https://www.microchip.com/en-us/development-tool/ADM00559Schematics:https://ww1.microchip.com/downloads/en/DeviceDoc/03-10241-R4.PDFfchk

author: bhj99
author_rank: Contributor
timestamp: May 04, 2023, 11:17:24 pm
content: Gotcha, so from your advice: I would say the I2C_CLK would correspond to the ADBUS0 clock output on pin 13 and I2C_SDA would be a bidirectional signal tying ADBUS1 and ADBUS2 together as depicted in Section 3.5.5 FT232H Pins used in an MPSSE of the FT232H datasheet?

author: langwadt
author_rank: Super Contributor
timestamp: May 04, 2023, 11:43:30 pm
content: https://learn.adafruit.com/adafruit-ft232h-breakout/i2c

author: mikerj
author_rank: Super Contributor
timestamp: May 05, 2023, 02:17:54 pm
content: Quote from: bhj99 on May 04, 2023, 12:11:06 amThe schematic for FTDI's own eval board (UM232H) is published : Page 22 in the following PDFhttps://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_UM232H.pdfBe careful with the FTDI I2C/USB devices if you need clock stretching, they do not all support this. I'm currently using the FT260 which does support clock stretching and is implemented as an HID device so no drivers are needed, but the downside is that throughput is limited to ~64kB/s