after a half year laying in a corner I tried to finish the assembling of my shruthi. after mixed up the 74xxx I ordered new vom conrad http://www.conrad.de/ce/de/product/155762/LOGIK-IC-M74HC595B1R-STM and http://www.conrad.de/ce/de/product/164453/CMOS-IC-74-HC-165-DIP/SHOP_AREA_17311&promotionareaSearchDetail=005 they aren’t actually the very same… is this maybe the reason why only the LED 1, 3, 5 and 7 are lighting? Or has anybody an idea what else I could have burned with my lousy soldering skills?
595 and 165 are made by many different manufacturers and there are several variants of them, but it doesn’t matter for the Shruthi, all variants should work.
LEDs 1, 3, 5, 7 are on when the Shruthi boots in firmware update mode. Normally, you need to press the S6 switch when powering on the unit to enter this mode. This indicates that for some reason, the Shruthi believe that S6 is continuously being held. This might be due to either:
- The pins 1 or 2 of S6 being shorted to ground
- The resistor network RN1 mounted backwards
- The pin 9 of IC2 being shorted to ground