Timeline for Problem with the reset circuit for a MCU
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
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| Jun 22, 2019 at 19:13 | answer | added | user9564464 | timeline score: 2 | |
| Jun 22, 2019 at 17:12 | answer | added | Justme | timeline score: 2 | |
| Jun 22, 2019 at 16:48 | comment | added | user9564464 | Many thanks for your fast responses! I just found the reason: I always only removed the mini-USB cable from the debugger (ST-Link V2), but had not removed the plug with the SWD&RST signals. Therefore the RST-pin was still connected to the unpowered debugger and got pulled-down by this... I am sorry, I thought the problem would lay inside the layout... | |
| Jun 22, 2019 at 16:32 | comment | added | TimWescott | The part has an internal pullup, so either the "RST" that exits your schematic to the right has something pulling it down, the processor is broken, there's a resistor installed where C11 should be, or there's a board fault. Is this the only board that's got troubles? Has your hardware person looked at it yet? | |
| Jun 22, 2019 at 16:31 | comment | added | joribama | Things you can try... Measure the voltage on the other side of R8 to confirm you do have 3.3V. If you have access to a soldering iron, disconnect one of the sides of R8, measure its resistance to confirm it's a 10kΩ part; disconnect one side of C11 and check if the voltage goes up (the capacitor may be defective). Measure the voltage on the other side of R9 and calculate the current in or out the NRST pin based on the voltage drop. Search your schematic to make sure there's nothing else connected to the RST net besides the debugger connector. | |
| Jun 22, 2019 at 16:25 | history | edited | user9564464 |
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| Jun 22, 2019 at 16:16 | history | edited | user9564464 | CC BY-SA 4.0 |
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| Jun 22, 2019 at 16:09 | comment | added | user9564464 | The MCU is a STM32 Cortex M0+: STM32L071K8 -> st.com/resource/en/datasheet/stm32l071v8.pdf | |
| Jun 22, 2019 at 16:04 | comment | added | Marcus Müller | What does the datasheet of the MCU (which MCU?) say about its NRST pin? Mabye that's simply pulled down internally with 9-10 kΩ. | |
| Jun 22, 2019 at 15:57 | history | asked | user9564464 | CC BY-SA 4.0 |