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PICLink

Last Update on:26/8/00

A new version of the PICLink is available now. The old version can be still viewed under e_plink_old.htm.

The new version seems to work better than the old version when used with slow calcs like the TI82 and TI85. The old version was working with the TI89 and TI92 but not with the slow TI82 and TI85. The new version has a different pin allocation and has a different program for the PIC16F84.

In the new version of TI's Graphlink Software, TI has introduced support for the old Black link which is compatible with the '$4 Serial Link'. So it might seems as if the PICLink isn't of any use anymore, but this is not true. It is still the only homemade link of Macintosh (althoug nobody has tested it with a MAC) and can be used to connect the calc to a modem.

New: Check this page to see how to patch TI's software (under Windows NT and Windows 2000) to make it work with the parallel link (='$5 link').

Introduction:
The PICLink enables data transfers between computers (PCs and MACs) and calculators from TI (TI7x, TI8x, TI9x...). This device is intended to be 100% compatible with the GrapLink from TI. Thus the GraphLink Software provided by TI can be used with this link.

This device converts data between the protocol used by the calc and the async-RS232 used by the computer. The calc sends and receives bytes in a special protocol using its 2 open-drain lines. The computers tranfers bytes using the serial protocl at 9600 bps, 8-Bit no parity and no handshaking.

The advantage of this link over the other homemade links (i.e. the "$5 parallel" and "$4 serial" links ) are:

Availability of software for newers calcs.
Can be used with MACs.
Can be used to connect the calc to a modem.

The disadvantage over the other homemade links is the relative high price. But still the PICLink is much cheaper than the real GraphLink from TI.

This links is also somewhat slower than the other links. I was amazed to find that WTran8x was faster to use ( personaly I find it much easier to use my software than TI's one).

The Tests:
I have tested this new version link between a 486 Notebook and a TI89 and it works fine with the GraphLink software from TI.
I have got also more than 30 responses saying that the previous version of the PICLink is working with the TI89 and the TI92.
If you build one then please drop me a mail and tell me if it works or not; Please tell me also if it works with the TI82, TI85, TI83 and TI86.

The Circuit:
The circuit is very simple and only a small number of parts is used: A PIC16F84, a resonator, 7 diodes, 6 resistors and a capacitor. The device takes its power from the serial port (RTS and DTR pins), so there is no need for an external power supply.

The circuit uses a cheap way to make the signal convertion between RS-232 level and TTL level, so cables must be short. The best way is to connect the device directly to the COM port.

The software for the PIC16F84 can be found here: Piclink.hex
When programming make sure you set the fueses to: XT + WDT_ON + PWRT+ON.

Future consideration:
In case there is anybody interested and providing cheap links, I will be able to make a PCB for the device. If I have the time, I might be able to sells preprogrammed PICs with the software already on them for those who don't have a PIC programmer. I will try also to sell complete kits for the link (like the ones for the IR Link). I do not know the price of those kits but it should be around 11UKP (=$18) which is much less than the price of the GraphLink from TI.

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Author : Sami Khawam