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I want to interface a PIC microcontroller (18f452) to a PC via the USB port. I learned that there is a USB class for serial communication so I will not have to write device drivers for it.

I want to know a simple way to connect my PIC to a USB port. I prefer a one IC circuit. Is there an IC that will do my job?

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  • \$\begingroup\$ The USB class for serial communications is not supported on Windows XP, so you need third-party drivers anyway. I'd say that using FTDI chips and their drivers is a decent way of going about it. The more recent FT230X chips are a nice choice IMHO. \$\endgroup\$
    – Kuba hasn't forgotten Monica
    Commented Jan 3, 2014 at 17:37

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The FT232R mentioned by Toby is the standard solution. FTDI has become the main supplier of USB connection solutions for microcontrollers and other logic devices. You install a Vitual COM Driver on your PC (downloadable from the FTDI website) and then you use the USB as a transparent communication channel for your UART. Means that the PIC will only see UART in and out, and the PC software will think the PIC is connected to a serial COM port.

enter image description here

This is the minimum configuration. As you can see that it's hardly more than the IC and the USB connector.

enter image description here

A breakout board like this one only needs ground Tx and Rx connections with the microcontroller. If necessary it can also provide the power supply for it.

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m.Alin mentions the Microchip MCP2200 as an alternative to the FT232R. I didn't know the device, and only had a quick look at the datasheet, but it looks promising: only half the price of the FT232R, and has both UART and GPIO. Breakout boards available:

enter image description here

(I'll study the datasheet a bit more tomorrow and report back.)

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The FT232L is a popular choice. It has drivers for all the main operating systems. There are breakout boards available.

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  • \$\begingroup\$ For a cheaper alternative, see MCP2200 \$\endgroup\$
    – m.Alin
    Commented Aug 23, 2012 at 18:30
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    \$\begingroup\$ @m.Alin - Thanks for the tip. Checked the datasheet only briefly, but looks good. Only half the price of the FT232R, and has both UART and GPIO. \$\endgroup\$
    – stevenvh
    Commented Aug 23, 2012 at 19:22
  • \$\begingroup\$ @stevenvh Interesting fact about the MCP2200 is that it's actually a pre-programmed PIC18F14K50 \$\endgroup\$
    – m.Alin
    Commented Aug 23, 2012 at 19:29
  • \$\begingroup\$ The MCP2200 is half the price of a FT232R, but needs an external crystal. The FT230X is about the same price as the MCP2200 and includes internal clock generation like the other FTDI chips. \$\endgroup\$
    – Jim Paris
    Commented Aug 23, 2012 at 19:48
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The MicroFTX would do what you want. It's an extremely tiny breakout board for FTDI's new lower-cost FT230X USB to serial chip. There are solder jumpers on the bottom that let you configure things like I/O voltage and power options.

MicroFTX top

MicroFTX bottom

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  • \$\begingroup\$ That design is a bit cavalier with ignoring the EMI choke on VBUS, and the 47pF impedance-matching capacitors on the DP/DM lines on the chip side. I'd not use it outside of the lab. Heck, for any production device using FTDI chips I'd in fact put both a USB differential choke on the data lines and a USB ESD protection. Those are all fairly tiny devices. \$\endgroup\$
    – Kuba hasn't forgotten Monica
    Commented Jan 3, 2014 at 17:36
  • \$\begingroup\$ It's only for the X-series chips that we get any ESD details at all, FT232R's datasheet is mum about it. For 232R I'd add USB ESD protection (say USBLC6). \$\endgroup\$
    – Kuba hasn't forgotten Monica
    Commented Jan 3, 2014 at 17:42
  • \$\begingroup\$ Agreed, this design has not been tested for EMI/FCC compliance, or USB spec compliance. FTDI provides hardware design guidelines that have a number of useful tips to follow for production devices. Those guidelines mention that all FTDI devices are tested for ESD protection to 2.5KV-3KV, and that things like capacitors to ground on DP/DM are optional and should be adjusted as needed during USB compliance testing. The 27Ω series termination is always required, so this board includes it. \$\endgroup\$
    – Jim Paris
    Commented Jan 14, 2014 at 20:15

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