From 2c0d80d4b157fb99e3129d5f03262a1885905c64 Mon Sep 17 00:00:00 2001 From: mahjongg2 Date: Fri, 16 Jul 2021 14:41:43 +0200 Subject: [PATCH] Update README.md --- README.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/README.md b/README.md index 26b227c..36dd9be 100644 --- a/README.md +++ b/README.md @@ -18,7 +18,7 @@ ZX81+38rev1,5.zip contains all gerber and drill files for the working updated an The file ZX81+38rev1,5.pdf is the schematic of the corrected revision 1.5 (in black and white) We found one more error, that I have fixed in revision 1,6: -the keyboard matrix is connected to eigh Address lines, A8 to A15, but the error is that for A8 a version is used that comes from the signal line passing through a 10K resistor (R1) so it is signal A8' , that is not correct, the keyboard needs unattenuated signals, so A8, not A8'. otherwise the resulting dataline does not go low enough to reliably register as "low". (actualy this was not essential, as long as the RP1 pullups are not too strong, so I changed them to 10K instad of 4K7. +the keyboard matrix is connected to eight Address lines, A8 to A15, but the error is that for A8 a version is used that comes from the signal line passing through a 10K resistor (R1) so it is signal A8' , that is not correct, the keyboard needs unattenuated signals, so A8, not A8'. otherwise the resulting dataline does not go low enough to reliably register as "low". (actualy this was not essential, as long as the RP1 pullups are not too strong, so I changed them to 10K instad of 4K7. And I will upload kiCad files after I know revision 1.6 is working well.