标签: working

Hi! Long time no see! Life has been busy over the past few months... Students' lives are busy... should be busy... especially for engineering students... I got an out-of-order ethernet switch, the symptom is that the switch cannot be powered on - no LED lit up, no response at all...   Fig. The switch was Level-one's FSW-2421 From previous experiences of many LCD monitors, the capacitors in the power module are getting swollen easily after using for a few years. The capacitances of those capacitor will decrease significanly. Replacing the swollen capacitors may help the monitor to work again... But for this switch, the capacitors looked good. None of them was swollen. Anyway, I decided to test all the capacitors in the power module... to just have a try...   Fig. Inside the switch (Left: Power module, Right: Main module) The power module converts 100-240V a.c. to +3.3V @ 3A.   Fig. Using soldering iron to desolder the capacitors   Fig. The old capacitors looked good (from left: 25V470uF, 16V1000uF, 16V1000uF and 10V470uF)   Fig. The capacitances of the capacitors (from left: 25V470uF, 16V1000uF, 16V1000uF and 10V470uF) Aha! The 10V470uF capacitor had problem! (The capacitance had decreased greatly in percentage!) After replacing the capacitor, it was working again!! Fig. The switch could startup normall P.S. Intended for more durable (to have longer lifetime again), all the 4 capacitors were replaced. Actually there was one another 400V big capacitor, but was not considered...

Sometimes it is good to keep our development tools and utilities up-to-date, since updates may have the bugs fixed and have more functions. I just replaced my MDK4.6 with MDK4.7a (verson Mar 2013). Fig.1 MDK updated to 4.7a   Surprisingly, I was unable to download the firmware (to a STM32 MCU) with my ULINK2 anymore... The IDE went out of response during program download... Fig.2 A ULINK2 to download program   Fig.3 The IDE went out of response... download program failed On the other hand, the 'COM' LED keeped on... No further response for a long time... Fig.4 The COM LED seemed to be on forever To solve this problem, many people on the Internet could think of downloading older firmware versions to the ULINK2 through the UART port by opening the casing. Fig.5 Pins soldered for UART firmware download   I did not download the old firmware successfully, the LPC2000 flash utility was not working stably after trying for several times, using CP2102 as the USB to TTL interface. Probably the CP2102 had baud rate timing problems... I don't know...   At the end, I found that increasing the 'Max Clock' in the configuration would totally solve the problem!! The default "Max Clock" was 1MHz, if we plug the ULINK2 into the USB, then we can choose "10MHz" as the clock.   Fig.6 Choosing "Max Clock" to be 10MHz, after plugging in the ULINK2   Everything was working fine since then... however, old projects still have to be re-configured before downloading them again to MCUs...