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Forum Index : Microcontroller and PC projects : MM+: Forget to remove JP1
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| miyek.ard Newbie  Joined: 31/03/2018 Location: MalaysiaPosts: 24 |
Hi peeps. I had a Micromite Plus LCD Backpack running perfectly without any bugs or errors. Initially I powered up the board using USB console at CON8, so I fit the jumper JP1. Then I changed the power connection from CON8 to CON1 (without removing the CON8 connection). But I forgot to remove the JP1! After some times running the MM+, the board cannot be connected to the PC anymore. It keep connect and disconnect itself from the PC. Same thing happen for any connection I made. Is it because of the JP1? How should I address this problem? |
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Azure Guru  Joined: 09/11/2017 Location: AustraliaPosts: 446 |
First if it is not to hard I would go back to USB only power on CON8 with JP! fitted and no other power source. If that works you know your USB power and everything on the MM is OK. Second, try powering it with JP! removed, no USB connection and power connected to CON1. If that powers up you know that the MM unit can run ok from you other power source. Third and finally, then try and connect your USB lead again just for data (jp1 removed) and power fed to CON1 you can see if there are any problems then. Let us know which of the three steps works or does not and what problems if any you notice. That will help us to help you if things are not working properly. |
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| miyek.ard Newbie Joined: 31/03/2018 Location: MalaysiaPosts: 24 |
Same problem No connection at all. Tera Term unable to recognize the serial port Same problem I want to clarify that the module can be connected to the PC. Tera Term able to trace the serial port. However, when I connect the Tera Term, the connection started being unstable  |
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palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 2006 |
There is a VERY stern warning in the Silicon Chip article about NOT having the jumper in place if you are using Con 1 for external power. I did read something in a thread here about it but can't remember where, but I suspect you have damaged something. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| miyek.ard Newbie Joined: 31/03/2018 Location: MalaysiaPosts: 24 |
I see. Thank you Paul! I just want to confirm regarding this matter  |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2463 |
if you plug a mouse or keyboard into that USB port on your PC, does that mouse or keyboard work? this will tell you if you have damaged your PC's USB port. cheers, rob :-) |
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MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
As shown it can happen by accident. It is the reason why i always use a 3 pin header with a single jumper. The pin in the middle will go to the circuit and the two outer pins are either USB or other power. You then have to choose between USB and other power source. Leave the jumper out, does not work but also no damage. Put the jumper on 1-2 or on 2-3 to select a power source. Dummy prove, but more important accident prove. Unfortunately using diodes is not working very well as it will lower the voltage to much for most regulators. So a 3 pin jumper is the next best thing. Microblocks. Build with logic. |
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| Azure Guru Joined: 09/11/2017 Location: AustraliaPosts: 446 |
I agree with robert.rozee, you should try and connect something you know works to your PC to see if the USB port still works or is damaged. That was what I suggested in step 1 of my post on the 16th and from your results posted today it sounds like it (your PC USB port) is not working properly anymore. If that port does not work you should be able to try a different USB port, like one on the back of your PC. Remember be careful and only test with either USB power only (JP1 fitted) and no external power connected OR external power only (jp1 removed). Easy mistake to make but sadly a costly one. |
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panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1116 |
Aimi, When you say "I changed the CON8 power connection to CON1", are you connecting ONLY 5V and GND to CON1? Where you say - how are you connecting the Micromite to the PC in this configuration? panky. ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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twofingers Guru Joined: 02/06/2014 Location: GermanyPosts: 1671 |
@MB How about a Schottky diode (eg 1N5818 ) or a MOSFET as reverse polarity protection? causality ≠ correlation ≠ coincidence |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
@twofingers. The problem is with USB and lots of USB cables. The voltage under load at the end of a USB cable is often just a little above 4 volts. Worst case i had was about 3V!!! Obviously that did not work. Took me some time to figure out it was the cable. If you add any kind of circuitry it drops alrady low voltage even lower. The mentioned Schottky diode has a voltage drop of about 0.5 volts making the voltage that goes into the circuit (often a 3.3v regulator) as low as 3.5-3.6v. That is not enough to make the regulator work reliably. A low dropout voltage is often between 0.5-0.7v. USB cables are often very thin cables that drop voltages significantly. If you want a circuit to work with most USB then the only way i found was to use a jumper and select a power source. Microblocks. Build with logic. |
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| twofingers Guru Joined: 02/06/2014 Location: GermanyPosts: 1671 |
I can confirm the issues with some of the USB cables. in my experience, those with the visible shielding work best. Just as information (I just checked it): The voltage drop for 1N5819 for 500mA is about 0.40V, for 200mA 0.36V. Anyway, I think it's worth trying to insert it into an existing PCB. I like your 3 pin design! Geoff has used it for the Maximites too (AFAIK).  causality ≠ correlation ≠ coincidence |
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Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1106 |
My CMM used diodes to isolate the USB 5V & the regulator 5V which meant that the 5V supply was really about 4.6V as implied above. I had an RF TXRX module that was playing up intermittently. I eventually cut the diode from the USB & bridged the diode from the regulator. Module is now much happier on the real 5V from the regulator. I agree that one or the other selection idea with jumpers is the better way to go. As an aside, I recently connected a TTL to USB adaptor to the CMM. Later on, I had need to power down the CMM. It didn't until I realised it was still receiving power via the new adaptor. Removing it's power lead fixed that. My 2c worth. ChopperP |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 816 |
I always cut the ends off usb leads that cease to function, and I am amazed that they dont actually catch fire in some cases. The thinest I have seen the actual copper inside was literally like a hair, it was almost invisible to the naked eye, yet it came from a tablet that was supplied with a 2.5A 5vdc usb plugpack for charging through the usb cable It was close to a meter long, pushing (well trying to) 2.5A to the tablet, through wires that can barely be seen... Replacing it with a different one cut the charging time almost in half, so I suspect that that usb cable was swallowing most of the power  |
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| miyek.ard Newbie Joined: 31/03/2018 Location: MalaysiaPosts: 24 |
Yes, the USB port works fine. Which jumper are you referring to? I only has one kind of jumper (Vbus)  Tx and Rx also connected. Refer image below.  Initially, I use CON8 as power and I fit JP1. Then, I changed to CON1 as power and CON8 for transferring data. The problem is I forgot to remove JP1 for my second connection! I checked the USB cable with other MM+ and it works fine. |
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| panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1116 |
@Aimi, From your answer above, I understand you are using a serial to USB module on CON1 and using it to supply power to the Micromite? Is this correct? If this is correct, can you tell us what voltage is being supplied by the serial to USB module? Have you confirmed that the USB port on your PC and the cable you use to connect to the Micromite are both good and work correctly with some other device? From your descriptions above, it sounds like you may have damaged either the Rx or Tx drivers on the serial to USB module or the Console Rx or Tx on the Micromite. As a further test, can you connect 5volts and ground to CON1 and ensure NO connection to the Tx and Rx pins, then with JP1 in, connect a known good USB cable to a known good USB port on your PC. Does this work? Does the PC recognise the USB connection to the Micromite? Just as an observation, if you had 5v connected on CON1 and jumper J1 in and 5v coming from the USB CON8, this should not cause any major damage with both voltages being the same, so something else must be causing problems. Also, as the Console and USB inputs to the Micromite use seperate pins, it is unlikely that both would be damaged. Let us know how you are going with your tests. panky ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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| Azure Guru Joined: 09/11/2017 Location: AustraliaPosts: 446 |
[quote]Which jumper are you referring to? I only has one kind of jumper (Vbus)[/quote] He was referring to another way to do it, not this design. Edit: Similar questions to Panky, we must have started typing at the same time. So I think you are saying: Tested PC USB port, it still works OK (I'm still not convinced that it is OK); Tested USB cable, it works with other MM's; MM+ that had JP1 left in does not work properly. For the MM+ that does not work properly anymore: It used to work before JP1 was accidentally left in and USB and ext power applied; It does not work with JP1 connected and just USB power/Tx/Rx connected (no ext power supply). Possibly the USB power side is damaged and it cannot provide enough power (compared to the other devide you plugged in to test it). Try removing the LCD and connecting the backpack to the PC with the LCD removed, it is still able to communicate with the PC and draw much less power. Also try using a different port like I suggested earlier. Do you have a multimeter or even better an oscilloscope? If you do check the input and output to/from the 3.3V regulator. You can check if there is any noise/ripple as well if you have an oscilloscope or just if the voltage is stable if you only have a multimeter. One last question, what are you connected between the PC and MM+ as your USB/Serial converter, is it working OK on your other MM's. Let us know your findings so we can try and help you find what has gone wrong. |
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