FTDI Picaxe programmer

 I needed to build a simple logic block for my Bread Board PBX to simplify the software and decided to use one of the PICAXE micro-controllers for a ring generator.

I had a couple of the small 8-Pin 08M2 chips already in my supplies, so I started to dig through my cables to find the special cable to use with the old AXE029 bread adapter to program the devices. It has been a while since I last programmed one, and I was using it via serial COM port cable the last time I did this and was not using the newer PICAXE USB cable that they have to connect to the adapter. Long story short, I could not get it to work. It may be a driver issue or because I am using the newer 8-Pin device now.

Anyway, I did some quick googling to see if I program a PICAXE with one of my other serial devices like my USB FTDI adapter HERE. The answer is yes!

Here is the minimal circuiy found HERE

But, I found using the FTDI 3.3v version the TX pin can go directly to pin3 without the resistor network and the RX to pin 7. And the PICAXE is being powered by the FTDI module too!

So, the setup just reduces to the following, but there is one more step required.

It turns out that the RX and TX signals need to be inverted to program the PICAXE. This is not a problem since there is a tool to make that change for you at FTDICHIP.com it is call FT_PROG (Windows).

Unzip FTProg tool, and run FT_PROG.exe.  Select Devices >> Scan and Parse, or just hit F5.

Your FTDI device will show up in the device tree.  click the + next to Hardware_Specific, then click on Invert_RS232_Signals.  Check the first 4 properties;

Invert TXD

Invert RXD

Invert RTS#

Invert CTS#

Click Devices >> Program or just hit CTRL + P

The Program Devices Dialog will appear.  Check the device to program, then click Program. 

This is very quick, but remember once you do this step, it will remain this way so, if you need to use it for something else you will need to revert this change.

As an alternative, you could use two inverters from a CD4049 hex inverter chip on the TX/RX lines and then you would not need the FTDI to be reprogrammed. I have not tested this yet, but it should work.