Category Archives: Serial Gadget

Posts related to my Serial Bit Rate Converter product.

Back in Stock

I was a little stuck for stock over July but I now have dozens of shiny new Bit Rate Converters. The new revision of the board has reverse-polarity protection so you cannot damage anything if the power is plugged in backwards. They are also robot-assembled in China. I was hand-building units for a while to cover the gap while I was waiting for the chinese boards to arrive but no more.

Crispy fried chips

130801105805870978994I got an RS232 bit rate converter in for repair today. Tests indicated that it boots up fine but converts data in one direction only. Also the indicator lights do not light.
I opened up the case and ho-lee-cow! Looks like some hell of a voltage surge happened here. Maybe it got hit by lightning.

I’ve seen some charred messes before but I cannot believe this board still mostly works. It boots up and can send and receive data even though the CPU and RS232 chip are charred husks. Unbelievable!

More design refinements to the Baud Rate Converter

The latest batch of RS232 Bit Rate Converters have a few improvements over the previous releases. The new model is called RS004. I’ve actually been selling these for a few months now so anyone who ordered some recently already has these new features:

  • Programmable time-delay in each direction so you can delay your packets.
  • Support for an even wider variety of baud rates from as low as 11bps up to 120,000bps – check the baud rate calculator
  • Improved power efficiency – It now only draws 25mA when idle, a bit more than that when busy but much less than the 120mA consumed by the previous design
  • Reverse polarity protection in case you accidentally wire the power backwards
  • I now outsource the circuit board manufacturing so I don’t have to build them myself. The boards are robot-assembled which results in a much neater build with less mistakes.

New units are now ready for sale, head on over to for more detail.

Ready to Go

Hooray, the next batch of boards has arrived after after a bit of an adventure – FedEx delivered them late and to the wrong address!

Fortunately it was a nice old lady down the street who received the boards and she brought them over to me. I now have stock. All you people holding off buying a Bit Rate Converter can place your orders now.


Remember those new boards I got yesterday? Well, they all sold today. Bam! just like that!

So I guess I’m still out of stock until the next batch arrives :(

First boards in from China

A sample batch of boards have arrived today. Hooray!

They all work. Hooray!

Overall I am happy with the boards and as an added bonus they are now RoHS compliant and look a lot neater than the hand-soldered ones.

There were a few downsides with the process though, the main one being the length of time it took to get it all happening. I’ve had delays and issues from just about everyone I have dealt with – DigiKey with their dumb export restrictions, FedEx taking foreeever to deliver stuff, Gold Phoenix for forgetting about the job until I reminded them a few times, PayPal for stuffing up my payments and sitting on my money for two weeks while the Aussie dollar went down and I lost out on the FX conversion… after all was said and done it took almost two months to make this happen and in the meantime I had run out of stock which is always embarassing.

In summary, I definitely think that offshore manufacturing can work for me but I’ll need to take all these delays into account and be organized well in advance the next time around.

Adventures in Outsourcing

I’m currently attempting to get a batch of RS232 Rate Converters made in China, I’ve been getting the PCBs etched in China for months now so this is the logical next step.

The biggest problem so far has been sourcing the parts. I’m getting most of the stuff from DigiKey because they specialize in smaller orders – I don’t have the sales volume to justify making 1000 of these things.

But get this. DigiKey will not deliver microprocessors to China, because of export restrictions, for a microprocessor that was made in China in the first place!

Ah well, I found MCUZONE, a Chinese supplier for the microprocessors thanks to the very excellent so I have all the parts on their way now.

So stay tuned, I’ll post photos when I get the assembled boards back from China.

UPDATE: I have since tried to buy more things through and have been defrauded. MCUZONE are good, but I was lucky to find them because honest sellers seem rare on Alibaba. Don’t trust them!

Overkill or Foresight?

The Serial Bit Rate Converter runs an ARM7 CPU which is complete overkill for the simple job of relaying serial data. I’ve often thought I should redesign it to run a cheaper and less powerful CPU like a PIC or AVR. I originally designed it with an ARM7 simply because I like them and enjoy programming them.

Another reason I never redesigned it for AVR is that the economics are not that great. It would probably take $5 off the price but cost me a couple of weeks of time to redesign the entire thing.

This decision has had an unexpected benefit recently. A customer asked me if I could add an extra function to search-and-replace byte sequences in the data stream. Now I’m really glad to have 50 MIPS on board because a smaller CPU might not have had the grunt to do the job.

So having a way-too-powerful CPU has produced a long-term benefit to enable me to quickly sieze a market opportunity.

First Production Volume Box

Finally I have all the parts and I spent last night assembling ten boxes to fill my first order. It looks not half bad.

Next I need to set up a web page and finalize pricing so anyone can buy one.

So what is a Volume Box I hear you ask? Well, the Volume Box is a digital stereo volume control. It has no knobs or buttons, it is controlled via serial commands from a PC or home automation system. It is intended to be used as a component in an automated audiovisual setup such as conference centres, classrooms etc.

Features include:

  • Attenuation from 0 to -95dB in 1dB steps
  • 3 way stereo input selector
  • Line level inputs and outputs
  • Optional 7 watt power amplifier
  • Mute function
  • Preset store and recall

Volume Box is Almost There

VolumeBoxPlugs-smallI’m getting orders for the Volume Box already. I haven’t even put up a web page for it. But wouldn’t you know it, the plastic case I want is not in stock with any of my regular suppliers (at least, those ones who are not still on extended Christmas holiday) so I’m having to get some cases flown in from England of all places so I can fill the orders. Of course I am going to have to absorb the extra cost of that, I wonder if Sony ever has these kind of supply-chain problems.