# ULPM LED weirdness **URL:** \ **Category:** mangOH Yellow\ **Created:** [February 21, 2020, 11:22pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827 "2020-02-21T23:22:22Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [February 21, 2020, 11:22pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/1 "2020-02-21T23:22:22Z")
Hey everyone, I’ve been playing around with ultra low power mode on the mangOH Yellow and have noticed some strange behaviors. I’m trying to troubleshoot an issue with a custom IoT module and I found these weird symptoms. I was wondering if anyone has any ideas what’s going on here. Without any IoT card inserted – if you touch the mangOH Yellow in the area near the power switch when it’s in ULPM, the power light blips on 3 times in approximately 1 second intervals. It looks like VCC\_5V0 is trying to turn itself back on? With the custom IoT card inserted – sometimes the LEDs on the mangOH Yellow board stay on after it enters ULPM. It looks like maybe VCC\_5V0\_EN is floating or something? I noticed that enable line ends up going directly to a GPIO pin on the WP7702. Does the WP7702 maintain the GPIO output states when it’s in ULPM? I couldn’t find a good answer to that question in the product specification document. Thanks for any ideas, Doug ---
**Author:** ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)\ **Post date:** [February 21, 2020, 11:25pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/2 "2020-02-21T23:25:25Z")
Did you modify your board in anyway? ---
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [February 21, 2020, 11:34pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/3 "2020-02-21T23:34:23Z")
I moved R607 to R608 to enable ADC3 on the IoT connector. I also moved R601 to R600 so I can supply USB\_VBUS through the IoT card instead of the USB port. Adding an external 1M pulldown on VCC\_5V0\_EN seems to somewhat help (seems to fix the LEDs staying on in ULPM, but doesn’t completely stop the blips when touching), but I’m not sure if there is a valid reason to be adding that or not… ---
**Author:** ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)\ **Post date:** [February 22, 2020, 10:33pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/4 "2020-02-22T22:33:04Z")
Is any part of your iot card touching the yellow board? Maybe the SIM/SD card connector. ---
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [February 24, 2020, 5:56pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/5 "2020-02-24T17:56:01Z")
No, nothing is touching. As far as I know, we completely followed the IoT card spec requirements. We don’t have any components on the bottom of the board. Is GPIO41 going to maintain its state keeping BUCK\_CONV\_EN low when the WP7702 goes into ULPM? It looks like BUCK\_CONV\_EN is floating in ULPM and allowing the 5V rail to sometimes turn on. Maybe I’m missing something? I can’t find anything in the datasheet saying what the GPIOs do when you enter ULPM. ---
**Author:** ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)\ **Post date:** [February 24, 2020, 7:57pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/6 "2020-02-24T19:57:58Z")
sounds like it is floating…I’ll need to check, ---
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [March 9, 2020, 11:16pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/7 "2020-03-09T23:16:32Z")
@asyal Have you had a chance to look at this any more? At first glance it seems like it would have to be a problem caused by my IoT card, but all of my diagnostics point to the 5V rail being allowed to stay on when it shouldn’t ---
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [March 16, 2020, 10:24pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/8 "2020-03-16T22:24:01Z")
@asyal Any updates? This is a pretty big deal for us, I’m kind of scared of putting our stuff in the field knowing that the battery is draining faster than it should ---
**Author:** ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)\ **Post date:** [March 16, 2020, 11:15pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/9 "2020-03-16T23:15:59Z")
It’s floating. Can you DNI BUCK\_CONV\_EN resistor R904? System should work seamlessly without it being present. ---
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [March 17, 2020, 5:38am UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/10 "2020-03-17T05:38:03Z")
Hi @asyal, Thanks for your response. I just removed R904. The system still works fine, but the LEDs are still staying on when it goes into ULPM. Any other ideas to try? ---
**Author:** ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)\ **Post date:** [March 17, 2020, 5:50am UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/11 "2020-03-17T05:50:52Z")
what particular LED is staying on in ULPM? We dont see any LED on in ULPM. ---
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [March 17, 2020, 2:43pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/12 "2020-03-17T14:43:21Z")
All 3 of the LEDs stay lit up (which is really more than 3 because they are multi-color): - D401 is yellow I believe - D402 is on - D500 is white The only logical conclusion I can reach is that VCC\_5V0 is still turned on ---
**Author:** ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)\ **Post date:** [March 18, 2020, 3:21am UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/13 "2020-03-18T03:21:37Z")
> [@dougbrown](#): > > The only logical conclusion I can reach is that VCC\_5V0 is still turned on We dont get that on any of our units. It seems the mod you made introduces the problem. Can you double/triple check your R600/R601 mod? ---
**Author:** ![dougbrown](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/dougbrown/32/2006_2.png) [@dougbrown](https://mangoh.discourse.group/u/dougbrown)\ **Post date:** [March 18, 2020, 3:18pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/14 "2020-03-18T15:18:25Z")
Hi @asyal, I really appreciate you looking into this. I just don’t know what to do next. I triple checked all of our mods (R601 -\> R600, R607 -\> R608, remove R904) and took pictures as I checked them. Obviously we also remove the jumper on CN801. Earlier I talked about adding a 1M pulldown that seemed to help, but that was on a different board so I’m working on a fresh one now without that mod. Here are the pictures to verify that we did the correct mods: R601 -\> R600: ![R601_R600](https://us1.discourse-cdn.com/flex016/uploads/mangoh/original/2X/7/7a9c8fd847e0fca9e9291f11985e9d2d9eb180c0.jpeg) R607 -\> R608: ![R607_R608](https://us1.discourse-cdn.com/flex016/uploads/mangoh/original/2X/7/749689ac9ebfcd939758dd9d9f3fa67500db9295.jpeg) Removal of R904: ![R904](https://us1.discourse-cdn.com/flex016/uploads/mangoh/original/2X/7/77c0a5501214dff190346d35a88bed8fa591f53a.jpeg) Just tested again this morning, and the LEDs all stayed on when it went into ULPM. I can’t remember if I’ve mentioned it, but it’s running from a LiPo battery when this happens, if that’s relevant at all. ---
**Author:** ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)\ **Post date:** [March 18, 2020, 3:54pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/15 "2020-03-18T15:54:39Z")
> [@dougbrown](#): > > Here are the pictures to verify that we did the correct mods: Do you have a fresh board? Are you running stock firmware? Can you measure VGPIO on R200 when its not in ULPM and when it is ULPM? ---
**Author:** ![johnofleek](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/johnofleek/32/51_2.png) [@johnofleek](https://mangoh.discourse.group/u/johnofleek)\ **Post date:** [September 29, 2022, 6:37pm UTC](https://mangoh.discourse.group/t/ulpm-led-weirdness/3827/16 "2022-09-29T18:37:18Z")
Two years later I was experiencing similar more potentially damaging issues whilst attempting to reduce the 200mA Idle current drawn by the mangoh yellow - for interest the WP7702 idle is \>3mA ![image](https://us1.discourse-cdn.com/flex016/uploads/mangoh/original/2X/7/719c660d954107397920c5e071b1cef5e3a99a5d.png) Turns out that my mangoh yellow has both R908 (supposed to be a NF) and R907 fitted Not a great combo if you also fit R909 - it connects 3V7 to 1v8 via a resistor Here’s the cct ![image](https://us1.discourse-cdn.com/flex016/uploads/mangoh/original/2X/1/1583c27335de708707d7e49f8fb30dfb91318fbb.png) Note that VGPIO is off if the WP is off - there is no way to POWER\_ON\_N the modem if U901 is OFF. and no way to connect something external to the WPs POWER\_ON\_N.