- DIY USB CONVERTER ADAPTER MOD
- DIY USB CONVERTER ADAPTER SERIAL
- DIY USB CONVERTER ADAPTER CODE
- DIY USB CONVERTER ADAPTER PC
Next, I soldered ground, RX, and TX wires from the FTDI chip to a pin header. (The ugly junk around the pins and under the chip is leftover plastic from the cover, a side-effect of the injection molding process.)
DIY USB CONVERTER ADAPTER SERIAL
I left it this way in case I wanted to add a switch in the future, allowing the same device to be used as a TTL or ordinary serial port. You can lift a pin just a little if you only want to disconnect it, or you can lift it and bend it back over the package like I did if you plan to solder wire onto the pin and the pad. I find it works best to nudge the pin sidewise with tweezers while heating it, then lift it. This is called lifting a pin and is often done by techs doing rework. Instead, I used my soldering iron to release the pin and gently pry up on it. I could have cut pin 22 with a knife but that is hard to reverse if I wanted to put it back. It turns out that the RX signal comes in from the serial port on pin 23 and goes out at the reduced TTL level on pin 22. I looked at the Sipe datasheet and did some investigation with my multimeter. However, I needed to disconnect the RX stage of the level shifter from the FTDI, otherwise there could be contention if my microcontroller was driving logic low and the FTDI was driving high. My plan was to bypass the level shifter and connect my TX, RX, and GND pins directly from my microcontroller to the FTDI chip since both run at 3.3V. It uses a series of capacitors in a configuration called a “charge pump” to step the voltage up or down to +/-10V, while requiring only a 3.3V source of power. The Sipex chip is a level converter, similar to the MAX232. The FTDI chip is quite common and does all the logic for the USB and serial protocols. I think the copied manufacturer is “Sipex”, so I used that datasheet. That’s usually the tell-tale sign that a part isn’t sold via retail and is only used by OEMs as a clone. If you search for the “Sipe” part, you will see a bunch of Chinese “part number squatters”. I think the Atmel is a serial EEPROM (8-pin, SOIC). Inside, I found it had a FTDI 232BL, Sipe SP213ECA, and Atmel 93C46.
![diy usb converter adapter diy usb converter adapter](https://cdn-shop.adafruit.com/970x728/2676-00.jpg)
It was covered with injection-molded plastic, so I had to use a knife to slice the edges and peel it back. That was the motivation I needed to tear into an adapter.
DIY USB CONVERTER ADAPTER MOD
He told me that most of them are built with a separate level converter IC, so it was likely I could mod one to get what I wanted.
![diy usb converter adapter diy usb converter adapter](https://content.instructables.com/ORIG/F8B/LHH3/GQBCJ6C2/F8BLHH3GQBCJ6C2.jpg)
I was hoping to scavenge one of the many ordinary USB-serial adapters I had lying around. I decided this would take too long though, so I got a second opinion from bunnie. You can dump an oscilloscope’s trace buffer to a file, then walk through the samples for your given channel and recover the original data. My first thought was to use one of my scope probes to capture the serial I/O and decode it in software. As I dug through my parts bin, I realized I didn’t have one of these FTDI cables and it was too late to buy anything. With AVR libc, it’s as simple as providing a “send byte” routine to a local copy of stdout, then calling printf() as usual. Since most microcontrollers these days have a built-in UART, debug prints can be added by configuring the clock divider for the given baud rate and monitoring a single pin (the RX pin).
DIY USB CONVERTER ADAPTER CODE
On a recent project, I needed to debug some code running in a microcontroller. So you can’t just use an ordinary USB-serial adapter, the kind used to connect an old PDA to your computer. One key difference is that the signals are LVTTL (0 – 3.3V) or TTL (0 – 5V), while ordinary serial is -10V to +10V. You can then interact with your target using an ordinary terminal program.
DIY USB CONVERTER ADAPTER PC
This cable provides a virtual serial port interface to the PC host and the normal serial signals at the target.
![diy usb converter adapter diy usb converter adapter](https://i.ebayimg.com/images/g/NoMAAOSw0rddb5ON/s-l300.jpg)
When interfacing with an external board over USB, it’s often easiest to use a USB-serial cable like the FTDI 232R. However, I recently have been working on some hobby projects in my spare time that are a good topic for some articles. I haven’t written much on this blog about my embedded work, mostly due to NDAs. When people ask about my day job, I tell them it is “designing/reviewing embedded security and cryptography”.