Tag Archive for 'USB'

ubbcom gets an upgrade

So a while back, I made a usb-to-serial converter board using FTDI’s most beloved chip: the FT232RL. This is the same chip that Sparkfun uses in their breakout boards. I just didn’t want to pay Sparkfun prices for something I could etch myself.

Well, I’ve given ubbcom a little upgrade.

First, I added the REN and RTS pins. The former is good for hooking the board up to a RS-485 level convert chip, since it can control the tri-state direction. The second I use along with the other handshake signals to bitbang program the ATtinys for bcard.

Additionally, I decided to actually bite the bullet and buy USB connectors. PCB approximations of USB connectors just don’t work. Really. They’re useless. So, I bought some connectors off of Digi-Key and made a footprint. I managed to actually orient the footprint the wrong way around the first time I tried this. That’s like the second time I’ve done this to USB connectors now. Nothing like epoxy to save the day there:

I chose to go with USB A connectors because I don’t trust mini connectors, they’re cheaper than micro connectors, and because I have USB extension cables, which work great. But yeah, now that I have a couple of these guys, it’s easy to communicate with chips, bitbang program them, etc.

USB RS232 – RS485 Converter

So for ACRIS, I designed a board that would take serial over USB and convert it to RS485 to send to all of the instruments.

Unfortunately, as it turns out, I made a crapload of mistakes on that board and my first attempt at soldering it did not turn out so well. I fixed the mistakes on the board (the worst being that the USB connector was actually freaking backwards), but I then began thinking a little more carefully about what I was trying to do.

It occured to me that the best way to design a USB -> RS485 converter would be to make it an actual dongle, like a flash drive or wireless dongle. The result is 2 inches long by .6 inches wide and has spots for 2 RJ-45 ports. It also uses the TXDEN signal to determine whether to send or receive data instead of just always placing the RS485 chip in transmit mode.

I’ll be sending an array of these out for ordering soon. I have to replace a few parts from the other board I designed, but other than that, it’s roughly the same as the previous ports.

One of my friends, Marcel, is a fantastic mechanical engineer. Perhaps he’ll be able to give me some guidance on building enclosures for these boards.