Most other applications for a serial comm cable use standard TTL polarity signals, so you won’t need the inverters. These are available from many sources in China, Taiwan, and Hong Kong. What else could you want? Figure 4 shows how you can use discrete transistors and resistors for the inverters. The chips are inexpensive, and the editing software for writing and testing the program is a free download.
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Select the miscellaneous parts per the version you are building.
There are at least four major suppliers of these chips worldwide: All you would need to add would be cables. FTDI-based boards use a built-in oscillator, so no external crystal is needed. For connections to the inverters, use tiny 30 gauge wire-wrap wire or strands from stranded hookup wire. No other programming equipment is required. The 22K and 10K resistors cannot be part of the cable. picaxw
Since most of the converter modules will operate up to Kb, you can use your cable for many computer interface projects other than PICAXE downloading. To package the additional inverter circuitry, attach a small perfboard extension to the end of the module axe02 with epoxy. Many hobbyists are reluctant to venture into new technology because of startup costs.
What else could you want? The cable uses an FTRx series converter — pjcaxe 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. 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.
For the others, you can add a couple of simple inverters. These picax available from many sources in China, Taiwan, and Hong Kong.
Building Your Own PICAXE Download Cable | Nuts & Volts Magazine
Pjcaxe article addresses that issue. Any type of NPN transistors can be used, and the resistor values are not critical. There is no standard pinout sequence. None of these boards have the capability of inverting RX and TX. Need to brush up on your electronics principles? 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.
Download cable using a converter module that can provide inverted RX and TX. 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.
After anchoring a three-conductor cable and testing the unit, cover the add-on board assembly with epoxy or heat shrink. That’s easily done in several ways. 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. There are many choices of similar ICs in a pin DIP package with through-hole leads, and many hobbyists prefer this type of package because it is easy to work with when using perfboard or a solderless breadboard.
The chips are inexpensive, and the editing software for writing and testing the program is a free download. Figure 4 shows how you can use discrete transistors and resistors for the inverters.
Building Your Own PICAXE Download Cable
My favorite is the board at the far right of Figure 3which is supplied with a protective outer wrapper of clear heat shrink tubing. Transistor inverters are inexpensive and parts are readily available. Most other applications ub a serial comm cable use standard TTL polarity signals, so you won’t need the inverters.
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. PICAXE products offer an attractive alternative to novices who lack experience using microprocessors and would like to learn more about them without a major investment in development tools and software training.
Figure 3 shows some examples.