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ECB-Cassette IF

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Home made alu bracket for the 3.5mm jacks.

I made both for 300 baud and checked if they could “talk” correctly to each other. (as in backup/restore).

Turns out I had to measure&select the timing capacitor C2 very precise to get 100% reliable interchangeable operation.

I have now “upgraded one of the board to 600baud.

I will modify the bracket to include the send/receive activity LEDs.

Info: This pcb has ground plane on both side so no problem with the screws.		ECB Cassette IF 300 and 600 baud
Cassette IF in action in a backplane-4: www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_speed3ple_images_img_20200329_231926small.jpg

Cassette IF signal out on Scope:

This is the “Kansas City” standard, one of several cassette formats in use at the time (mid 70's).

Kasas City format use an continuous audio stream of a tone and shift that tone between 2400hz and 1200hz to indicate 1 or 0.

8 cycles of 2400hz represent a “1” bit or a MARK and

4 cycles of 1200hz represent a “0” bit or a SPACE. 		www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_speed3ple_images_img_20200329_230632small.jpg

Cassette Interface in use:

To send a file to tape: PIP PUN:=<filename.hex>[E]

www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_speed3ple_images_img_20191013_011746small.jpg
Cassette IF and technical document: www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_speed3ple_images_img_20200405_211813small.jpg
Interconnecting 2 SBC and sending/receiving data through audio cable at 300baud: