From 05c52e7390744e28d1a35d55472f90bd0511420c Mon Sep 17 00:00:00 2001 From: Werner Almesberger Date: Wed, 7 Sep 2011 04:50:44 -0300 Subject: [PATCH] labsw/LOG: reworked power supply bypassing --- labsw/LOG | 35 ++++++++++++++++++++++------------- 1 file changed, 22 insertions(+), 13 deletions(-) diff --git a/labsw/LOG b/labsw/LOG index 57ddefa..5870fad 100644 --- a/labsw/LOG +++ b/labsw/LOG @@ -150,6 +150,28 @@ Milled face plate #3: LEDs to the pull-ups. Work-around: add 10 kOhm in parallel to each LED. +--- Wed 2011-09-07 ------------------------------------------------------------ + +Rework: +- problem: labsw occasionally (around 1% of all cycles in an automated + test loop) gets some configuration bits wrong. The pattern observed + so far is that, in an attempt to turn on CH1, then CH2, CH1 comes on + normally while CH2 either doesn't come on at all or the relay switches + but the LED doesn't. +- analysis: + This may be a problem with the power supply or with USB. Consider + some or all of the following improvements: + + - follow SiLab's recommendations for regulator bypassing more closely + - enable the VDD monitor to catch brown-outs + - add ground areas to shield CPU and USB + - add redundancy to EP0 protocol + - add bead to relay power, to prevent upsetting the 5 V rail +- rework: + Implemented power supply bypassing according to SiLabs' recommendations: + - added 4.7 uF in parallel to C1 + - added 100 nF in parallel to C2 + --------------------- (next PCB run) @@ -174,16 +196,3 @@ Pending: 3) drive opto LEDs from 3.3 V instead of 5 V (NOT ! Regulator can only provide 100 mA, which wouldn't be enough if more than two opto-couplers are active.) -- labsw occasionally gets some configuration bits wrong. The pattern - observed so far it that, in an attempt to turn on CH1, then CH2, CH1 - comes on normally while CH2 either doesn't come on at all or the - relay switches but the LED doesn't. - - This may be a problem with the power supply or with USB. Consider - some or all of the following improvements: - - - follow SiLab's recommendations for regulator bypassing more closely - - enable the VDD monitor to catch brown-outs - - add ground areas to shield CPU and USB - - add redundancy to EP0 protocol - - add bead to relay power, to prevent upsetting the 5 V rail