AXE027 USB clone?

Hi, I ordered some PICAXE parts and forgot to order a USB programmer! However I have some FDTI modules, specifically the MM232R which uses the same FT232RQ chip as the AXE027 here is a link to the part :- http://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_MM232R.pdf

The schematic is almost identical to the AXE027. Regarding the FT232RQ chip, the Vendor ID is the same = 0x0403. But the standard FDTI Product ID = 0x6001 versus the unique ID for the AXE027 USB cable = 0xbd90

After playing with this for hours, in desperation I finally used FDTI tools to remove all instances of FDTI drivers. Changed the Product ID to 0xbd90 using an FDTI tool and installed the Self extracting pre-installer software and then plugged in my MM232R.

Good news, the PICaxe software detected the FDTI module, and I now in Device Manager - Ports - I have AXE027 PICAXE USB (COM4) - Wonderful, job done right?

NO! When I run PICAXE Programming editor - View - Options - serial Port, I see COM4 AXE027 PICAXE USB (ready for use) - Show Port Help tools - TEST PORT.

It says that when the LED is OFF the signal should be 0vdc, and when the LED is ON the signal should switch HIGH.

The problem is that I am getting the exact opposite of this! (ie. when the LED is OFF the signal is HIGH.)

Some questions.

1. How can this be possible, I have the same chip part number, using the AXE027 driver. Could it be that the AXE027 firmware is modified to use inverted TxD and RxD data?, ie should I introduce two data invertors (ie. getting desperate!)
2. The serial echo test works. If I link the serial Rxd to TXd it echos whatever I type on the terminal.
3. I am using the PICAXE14M2 chip.
4. When I put power on the chip I see a repeating short string followed by a delay from the TXD pin. I cannot determine what this string is but at 2400 baud it displays like this :- »Bm]âq}ÌûÉDa»Bm]âq}Ì{ÉDa»Bm]âq}Ì{IDa;B]âq}ÌûÉDa;B]âq}ÌûÉDa
5. I was hoping to use the 3.3v @50 m/a available from the FDTI chip to power and PICAXE 14M2. Question, Once (hopefully) I get the programming and debugging etc working - should this be possible using 3.3vdc, or must I program and test the device at 5vdc?

Please help, I am getting really frustrated on something that I thought would be plain sailing!

You can program the FTDI chip to invert the RX and TX signals using the FDTI utility.

Hi, well after hours and hours of grief, and after my first post I decided to hookup a logic analyzer to see if I could make sense of the data string emitted by the PICAXE14m2. I eventually found out that it is inverted data at 4800 baud. Which you seem to indicate is the problem. Thanks I will try to hunt down the FDTI utility, then maybe I can finally get things working. I hope then that question #5 is then able to work.

So for anyone new to this, if you use a standard FDTI part - invert the data!

Here is the PICAXE 14m2 data output after inversion

Success! Partly thanks to Goeytex.

1. You can use a standard USB to RS232 FDTI part MM232R, or similar. But do the following. Using the FDTI utility FT_PROG.exe
a). Change the Product ID to the unique ID for the AXE027 USB cable = 0xbd90 (from 0x6001)
b). Invert RS232 Signals for TXD and RXD to inverted data

2. Now install the Self extracting pre-installer software CDM20814_Setup.exe

Now plug in the USB RS232 device and the pre-installed software will detect it and use the AXE027 PICAXE USB description.

3. I can confirm that the MM232R part can be configured into the USB bus powered mode. The 3.3vdc on board regulator powers the PIXAXE 14-M2 part fine.

4. Edit 19th Feb 2012. Note the MM232R module does not include the AXE027's two 10k pull down resistors on the TX and RX lines. These are required and should be installed.

GrahamGo said:

Success! Partly thanks to Goeytex.

1. You can use a standard USB to RS232 FDTI part MM232R, or similar. But do the following. Using the FDTI utility FT_PROG.exe
a). Change the Product ID to the unique ID for the AXE027 USB cable = 0xbd90 (from 0x6001)
b). Invert RS232 Signals for TXD and RXD to inverted data

2. Now install the Self extracting pre-installer software CDM20814_Setup.exe

Now plug in the USB RS232 device and the pre-installed software will detect it and use the AXE027 PICAXE USB description.

3. I can confirm that the MM232R part can be configured into the USB bus powered mode. The 3.3vdc on board regulator powers the PIXAXE 14-M2 part fine.

Click to expand...

Well done for persisting with the problem.

One question: is the configuration a once-off thing or do you need to configure the port/driver each time the PC is booted?

is the configuration a once-off thing or do you need to configure the port/driver each time the PC is booted?

Click to expand...

One time, as the configuration data is retained in the FT232RQ EEPROM.


A Couple of things:

While the 3.3v Regular can power a Picaxe, it may not be suited to applications that have high I/O loads. eg lots of LEDs illuminating at the same time. The Picaxe itself can safely source up to 80 - 100 ma combined total to its I/Os. Any supply for the Picaxe should be able to supply at least that much, except in low power applications.

The MM232R's 3V3 pin can only supply up to 50mA which is fine for stand alone programming or blinking 1 or 2 LEDs, but probably not for powering a Picaxe on a breadboard where there is considerable I/O load.

The FTDI module can be configured for 1.8, 2.8, 3.3 or 5v I/0 output. The AXE027 is configured for 5V since Picaxe inputs pins are 5V tolerant at lower Vcc levels. See the FTDI Datasheet for configuration details

Agreed, but in this case all I want is to attach a graphics LCD, a couple of switches, an eeprom and the USB to pull the data out with. In retrospect I see that I probably went a step too far by changing the Product ID. It would have been fine to just invert the data and use the standard driver that Windows installs, But you live and learn. You will gather from my 1st post that I was getting fairly frustrated. This is my first time using Picaxe, at least now I can enjoy it. My most recent experience is with the ARM family, a great family. But way over the top for what I want to do right now.