None of these boards have the capability of inverting RX and TX. The cable uses an FTRx series converter — a chip found in many USB-to-serial converters because of its versatility, as well as the availability of drivers for a wide variety of operating systems. FTDI-based boards use a built-in oscillator, so no external crystal is needed. They keep the PICAXE serial input from floating around like an antenna when the download cable is disconnected, which could result in noise pickup that might interfere with program execution. There is one catch, though.
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Transistor inverters are inexpensive and parts are readily available.
To package the additional inverter circuitry, attach a small perfboard extension to the end of the module board with epoxy. All you would need to add would be cables. This article addresses that issue. Learning Electronics Need to brush up on your electronics wxe027 Figure 4 shows how you can use discrete transistors and resistors for the inverters.
These are available from many sources in China, Taiwan, and Hong Kong. Need to brush up on your electronics principles?
Many hobbyists are reluctant to venture into new technology because of startup costs. The chips are inexpensive, and the editing software for writing and cabel the program is a free download. Any type of NPN transistors can be used, and the resistor values are not critical. Most other applications for a serial comm cable use standard TTL polarity signals, so you won’t need the inverters.
For the others, you can add a couple of simple inverters. You can temporarily power your PICAXE circuit from the module, but for a final design use something that works when the download cable is unplugged. Note that the 22K and 10K resistors from Figure 2 are still necessary to prevent noise on the serial input when the cable is disconnected. The cable uses an FTRx series converter — a chip found in many USB-to-serial converters because of its versatility, as well as the availability of drivers for a wide variety of operating systems.
None of these boards have the capability of inverting RX and TX. No other programming equipment is required. Figure 3 shows some examples. Select the miscellaneous parts per the version you are building. There is one catch, though.
To test your completed cable — including the inverters — jumper pin 1 to pin 2, and then use Windows HyperTerminal or any other serial comm utility software to perform a loopback test. Download cable using a converter module that can provide inverted RX and TX.
FTDI-based boards use a built-in oscillator, so no external crystal is needed. In summary, there are ways that PICAXE could have made it difficult to substitute third-party download cables, but to their credit there is no evidence they have attempted to do that. Figure 1 lead photo shows details of the PCB assembly removed from a recently acquired AXE cable and its schematic.
They keep the PICAXE serial input from floating around like an antenna when the download cable is disconnected, which could result in noise pickup that might interfere with program execution. There are at least four major suppliers of these chips worldwide: The 22K and 10K resistors cannot be part of the cable. The PCB is a bit of an overkill, with top, bottom, and intermediate ground ccable layers.
What else could you want? There is no standard pinout sequence. PICAXE products offer an attractive alternative to novices who lack xable using microprocessors and would like to learn more about them without a major investment in development tools and software training. After anchoring a three-conductor cable and testing the unit, cover the add-on board assembly with epoxy or heat shrink.
You can buy a postage stamp-sized MCP breakout board direct from the manufacturer Microchip or from major electronics suppliers Digi-Key, Mouser, Newark, Farnell, etc. Purchasing a ready-made converter module or breakout board can save you the tedious job of soldering the small closely-spaced pins of a converter chip.
My favorite is the board at the far right of Figure 3which is supplied with a protective outer wrapper of clear heat shrink tubing.