Werner's Miscellanea
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Werner's Miscellanea Commit Details
Date: | 2011-09-07 09:50:44 (12 years 6 months ago) |
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Author: | Werner Almesberger |
Commit: | 05c52e7390744e28d1a35d55472f90bd0511420c |
Message: | labsw/LOG: reworked power supply bypassing |
Files: |
labsw/LOG (2 diffs) |
Change Details
labsw/LOG | ||
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150 | 150 | LEDs to the pull-ups. Work-around: add 10 kOhm in parallel to each |
151 | 151 | LED. |
152 | 152 | |
153 | --- Wed 2011-09-07 ------------------------------------------------------------ | |
154 | ||
155 | Rework: | |
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 | ||
153 | 175 | --------------------- |
154 | 176 | |
155 | 177 | (next PCB run) |
... | ... | |
174 | 196 | 3) drive opto LEDs from 3.3 V instead of 5 V (NOT ! Regulator |
175 | 197 | can only provide 100 mA, which wouldn't be enough if more than |
176 | 198 | 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 |
Branches:
master