Date:2011-09-07 09:50:44 (7 years 9 months ago)
Author:Werner Almesberger
Commit:05c52e7390744e28d1a35d55472f90bd0511420c
Message:labsw/LOG: reworked power supply bypassing

Files: labsw/LOG (2 diffs)

Change Details

labsw/LOG
150150    LEDs to the pull-ups. Work-around: add 10 kOhm in parallel to each
151151    LED.
152152
153--- Wed 2011-09-07 ------------------------------------------------------------
154
155Rework:
156- problem: labsw occasionally (around 1% of all cycles in an automated
157  test loop) gets some configuration bits wrong. The pattern observed
158  so far is that, in an attempt to turn on CH1, then CH2, CH1 comes on
159  normally while CH2 either doesn't come on at all or the relay switches
160  but the LED doesn't.
161- analysis:
162  This may be a problem with the power supply or with USB. Consider
163  some or all of the following improvements:
164
165  - follow SiLab's recommendations for regulator bypassing more closely
166  - enable the VDD monitor to catch brown-outs
167  - add ground areas to shield CPU and USB
168  - add redundancy to EP0 protocol
169  - add bead to relay power, to prevent upsetting the 5 V rail
170- rework:
171  Implemented power supply bypassing according to SiLabs' recommendations:
172  - added 4.7 uF in parallel to C1
173  - added 100 nF in parallel to C2
174
153175---------------------
154176
155177(next PCB run)
...... 
174196  3) drive opto LEDs from 3.3 V instead of 5 V (NOT ! Regulator
175197     can only provide 100 mA, which wouldn't be enough if more than
176198     two opto-couplers are active.)
177- labsw occasionally gets some configuration bits wrong. The pattern
178  observed so far it that, in an attempt to turn on CH1, then CH2, CH1
179  comes on normally while CH2 either doesn't come on at all or the
180  relay switches but the LED doesn't.
181
182  This may be a problem with the power supply or with USB. Consider
183  some or all of the following improvements:
184
185  - follow SiLab's recommendations for regulator bypassing more closely
186  - enable the VDD monitor to catch brown-outs
187  - add ground areas to shield CPU and USB
188  - add redundancy to EP0 protocol
189  - add bead to relay power, to prevent upsetting the 5 V rail

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