Category Archives: Serial Gadget

Posts related to my Serial Bit Rate Converter product.

First Prototype Volume Box

The first completed unitThe Volume Box board is assembled and tested, the last few firmware bugs are squished and the only thing missing now is the machined end panel for the plastic case and it is ready to sell!

Here are the lessons I have learned:

1. PICs can be a mighty pain in the bum to debug, particularly the peripherals. I think I’ll use a different chip next time.

2. Always check your component footprints when designing a PCB, the Protel footprint libraries are full of errors. I’ll be patching the first run of boards due to a bad footprint.

3. Don’t try to get a product out the door around Christmas time, many manufacturing companies are closed for the holidays especially here in Australia where we combine our summer holiday and Christmas holiday into one big long holiday. Some companies do not resume business until January 18th!

Anyway, now the design is proven I have ordered some parts to begin producing these things.

PCB for Volume Box

VolumeBoxPCBI’ve finally taken delivery of my first batch of printed circuit boards for the Volume Box. They look real nice. As usual I got them from Gold Phoenix of Shanghai – The quality of the boards is pretty good and their prices are good for very small runs.

My chips and other parts have already arrived so next I need to assemble it and test. I’ve still got a lot of tasks after that before it is a finished product such as designing the end panels of the box, writing the user manual and setting up a website for it.

And Out the Door they Go!


Sales of the RS232 Rate Converter were a little slow throughout October and November but they sure have caught up in the last couple of weeks. I thought I had enough stock to see me through until January but after a flurry of orders, I am now completely sold out.

So I’ve been frantically ordering parts to build more units ASAP. I suppose having too many orders is a good problem to have, better than having no orders.

I’ve no idea why sales have suddenly surged, it’s not the kind of thing you’d buy as a Christmas present!

Time for a new Product

VolumeBoxPrototype2Well, the RS232 Rate Converter is pretty mature now. It does it’s job well and there is not a lot of improvements to make to it anymore. So what to do next?

I’ve been talking with a friend in the home automation business and he reckons there’d be a small market for an RS232 controllable volume control. This device would allow a home automation processor to control the volume on an amplifier which does not have any other means of remote control.

Now I thought that would be a pretty simple thing for me to make so I built a prototype. It only took me three evenings to cobble together something that works, thanks mainly to RS Components‘ free next-day shipping for electronic parts. I think this will be my next product.

Of course I can’t sell it in this state, it’s funny but taking a product from prototype to production is usually more work than making the prototype in the first place.

Serial Bit Rate Converter Revision 3 Released

RS003I’ve just built the first of my new revision 3 RS232 Bit Rate Converter. It has the following improvements:

  • Cleaner, more stable RS232 output signal
  • Can accept a range of power supply voltages from 5V up to 12V
  • Has a professionally designed and printed vinyl label instead of the rather amateurish ones I was making myself

The design is mature now. I am impressed by the device’s reliability. I’ve been selling these things for almost a year now and haven’t had a single unit fail.

I’ve also put the Silicon Sparrow logo on the label. I’m going to do that to all my products from now on to try and gather them into a common brand.

Why not pop over to to read more about this device or even buy one!

Pricing change for Serial Gadget

After looking at my sales figures, it seems the majority of my RS232 Rate Converter sales are going to America. I’ve only sold two into Australia ever, so it seems to me that pricing it in Australian dollars is not appropriate for this product, especially since the Australian dollar has been moving quite a lot in relation to the greenback in recent weeks.

The new price is US$ 89.00.

Part Substitution a-go-go!

One of my peeves about the electronics business is the poor availability of parts. I’d found this brilliant AP1115 power regulator from Diodes Inc. which I’ve been using for months in my RS232 Rate Converter but now, you can’t get them anymore. I haven’t found a supplier who stocks this part since June and my own stock has run out.

Fortunately, I have found the MCP1703 from Microchip which is compatible and will do as a substitute. But now I can’t get the particular Atmel microprocessor I use, well not in small quantities anyway and I am not ready to order 1000 of them based on the sales I’m getting at the moment. So I’ve had to go up a model and get a more expensive microcontroller which is pin-compatible but I’ll have to change the firmware to make it work. This is the third time I’ve had to tweak the design of this product due to unavailable parts in the last 12 months. Such is the fun of the electronics biz!

Some Small Website Improvements for

Looking at the RS232 Bit Rate Converter website, I thought it needed more documentation so potential customers can find out more about the product before committing to buy one.

So I now have an FAQ and I added more details to the user manual, more than doubling it’s length. The user manual is now available in PDF format and also HTML for reading online.

I was also considering setting up a blog on the Serial Gadget website but I found a neater solution. By using a PHP RSS reader, I can automatically find any articles I write on Silicon Sparrow blog (such as this one) which are relevant to the Serial Gadget website and summarize them on a “News” page on That’s one less blog I need to manage.

Having a News page is also good for customers as they can see that the site is still being updated and is not one of the many zombie dead abandoned sites which abound on the global internet.