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#11
ESP32 / Re: ESP32-POE problems on just...
Last post by LubOlimex - November 07, 2025, 08:56:02 AMThere is physical reason by design for this behavior. Check D4 diode on the GPI36 wire, diode is near the UEXT and it leads to this continuity behavior.
Diode is placed to prevent accidental parasitic powering via the UART. If you are good enough with the soldering iron you can remove the diode and solder the pads together, this will lead to similar behavior as other pins at the UEXT.
Notice that GPI34 is only input regarding the ESP32 chip, this is by Espressif design, hence we decided to name the wire as GPI34 (as opposed to GPIO34).
Diode is placed to prevent accidental parasitic powering via the UART. If you are good enough with the soldering iron you can remove the diode and solder the pads together, this will lead to similar behavior as other pins at the UEXT.
Notice that GPI34 is only input regarding the ESP32 chip, this is by Espressif design, hence we decided to name the wire as GPI34 (as opposed to GPIO34).
#12
UEXT / Re: Lost continuity to UEXT on...
Last post by LubOlimex - November 07, 2025, 08:47:33 AMSo far there are no signs of hardware issue.
"Checked the ESP32-POE-16MB board itself, and there is no continuity for GPI36 between EXT (board edge pin header) and the corresponding UEXT pin! All other GPIO's found on both show continuity, just not this one pin."
The is expected. There is diode on the GPI36 near the UEXT that leads to this behavior. Refer to the schematic.
Just to confirm it myself I tried to beep GPI36 at pads of UEXT and EXT2 on few boards here and surely there is no beep here either.
"Checked the ESP32-POE-16MB board itself, and there is no continuity for GPI36 between EXT (board edge pin header) and the corresponding UEXT pin! All other GPIO's found on both show continuity, just not this one pin."
The is expected. There is diode on the GPI36 near the UEXT that leads to this behavior. Refer to the schematic.
Just to confirm it myself I tried to beep GPI36 at pads of UEXT and EXT2 on few boards here and surely there is no beep here either.
#13
ESP32 / ESP32-POE problems on just UEX...
Last post by KeviNH - November 06, 2025, 10:22:41 PMHas anybody seen an issue where Post in UEXT subforum?
Specifically we are using a ESP32-POE-16MB, connecting to Serial1 (on GPI36) via the UEXT, and in a deployed device it became unreliable sporadically,then yesterday just stopped working entirely. A multimeter shows no continuity between the board edge EXT for GPI36 and the corresponding pin on the UEXT.
Not seeing any physical reason for this fault, no unusual mechanical stress on the ESP32-POE-16MB board.
Specifically we are using a ESP32-POE-16MB, connecting to Serial1 (on GPI36) via the UEXT, and in a deployed device it became unreliable sporadically,then yesterday just stopped working entirely. A multimeter shows no continuity between the board edge EXT for GPI36 and the corresponding pin on the UEXT.
Not seeing any physical reason for this fault, no unusual mechanical stress on the ESP32-POE-16MB board.
#14
UEXT / Lost continuity to UEXT on jus...
Last post by KeviNH - November 06, 2025, 10:14:16 PMWe are using Serial1 and I2C via the UEXT connector on ESP32-POE-16MB.
Yesterday on one device, Serial1 stopped responding. Checked our connections and we have continuity through to our UEXT jumper.
Checked the ESP32-POE-16MB board itself, and there is no continuity for GPI36 between EXT (board edge pin header) and the corresponding UEXT pin! All other GPIO's found on both show continuity, just not this one pin.
Has anybody else experienced a similar issue? We had an unexplained failure a while back on an ESP32-POE which might also have a similar fault, we had a spare for that one and so just swapped it out without a lot of diagnosis.
Yesterday on one device, Serial1 stopped responding. Checked our connections and we have continuity through to our UEXT jumper.
Checked the ESP32-POE-16MB board itself, and there is no continuity for GPI36 between EXT (board edge pin header) and the corresponding UEXT pin! All other GPIO's found on both show continuity, just not this one pin.
Has anybody else experienced a similar issue? We had an unexplained failure a while back on an ESP32-POE which might also have a similar fault, we had a spare for that one and so just swapped it out without a lot of diagnosis.
#15
A64 / Re: PE16/POWERON PIN with 1k r...
Last post by mauricio - November 06, 2025, 06:17:13 PMHello, thanks for answer.
I soldered a 0603 1k (carefuly drifted) resistor on pad R28, near to R65, which is populated.
The situation is now power button acts more like a reset, than a power button.
It boots with no problem. If I press any, original pwron1 button or PE16 to gnd, system reboots, no shutdown. I'd like it to shutdown and stay off.
The resistor is still there, because is kind of tricky to put it on there. I sort of remember before I put that resistor, pressing pwron1 button shuts down the system and it remains off. Is that way right ?
I soldered a 0603 1k (carefuly drifted) resistor on pad R28, near to R65, which is populated.
The situation is now power button acts more like a reset, than a power button.
It boots with no problem. If I press any, original pwron1 button or PE16 to gnd, system reboots, no shutdown. I'd like it to shutdown and stay off.
The resistor is still there, because is kind of tricky to put it on there. I sort of remember before I put that resistor, pressing pwron1 button shuts down the system and it remains off. Is that way right ?
#16
A64 / Re: PE16/POWERON PIN with 1k r...
Last post by LubOlimex - November 06, 2025, 09:47:35 AMNo idea, it should be explained in AXP803 datasheet.
Did you keep the PWRON to GND all the time? If you release the GND connection the AXP803 is supposed to boot.
Did you keep the PWRON to GND all the time? If you release the GND connection the AXP803 is supposed to boot.
#17
A64 / PE16/POWERON PIN with 1k resis...
Last post by mauricio - November 05, 2025, 04:13:22 PMHello.
After discovering the PE16 pin 37 at GPIO has R65, but no R28, I solder one there
Now when connect GND to pin 37, A64 poweroff, but reboot. I would like it remain off
Is there's something else to do to achieve a poweroff with PE16 ?
Thanks
After discovering the PE16 pin 37 at GPIO has R65, but no R28, I solder one there
Now when connect GND to pin 37, A64 poweroff, but reboot. I would like it remain off
Is there's something else to do to achieve a poweroff with PE16 ?
Thanks
#18
UEXT / Re: ESP32-PoE-ISO-16MB --> MOD...
Last post by LubOlimex - November 05, 2025, 11:19:31 AMIt is clear then. In your case MOD-BME280 won't get powered properly. Basically the 3.3V output from MOD-IO is disconnected. In the way you use it, MOD-BME280 gets parasitically powered via the I2C lines. This is side effect and a problem, it is not a feature or a recommended way to use the boards together.
In order to enable the 3.3V output at the UEXT_FEMALE header, you need to solder R16 on MOD-IO board. It is located just under the UEXT_FEMALE connector on the top of the board.
We've disabled this 3.3V line by default to avoid short-circuits when multiple MOD-IO boards are connected (and each powered from own power supply). But in your case you need to simply solder 0R resistor size 0603 on R16 pads and things will start working properly.
Again refer to the schematic to understand better:
https://www.olimex.com/Products/Modules/IO/MOD-IO/resources/MOD-IO-schematic.pdf
The alternative is to connect MOD-IO and MOD-BME280 in parallel (e.g. not MOD-BME280 after the MOD-IO). This way MOD-BME280 will get powered from ESP32-POE-ISO (where 3.3V output on the UEXT is enabled by default).
In order to enable the 3.3V output at the UEXT_FEMALE header, you need to solder R16 on MOD-IO board. It is located just under the UEXT_FEMALE connector on the top of the board.
We've disabled this 3.3V line by default to avoid short-circuits when multiple MOD-IO boards are connected (and each powered from own power supply). But in your case you need to simply solder 0R resistor size 0603 on R16 pads and things will start working properly.
Again refer to the schematic to understand better:
https://www.olimex.com/Products/Modules/IO/MOD-IO/resources/MOD-IO-schematic.pdf
The alternative is to connect MOD-IO and MOD-BME280 in parallel (e.g. not MOD-BME280 after the MOD-IO). This way MOD-BME280 will get powered from ESP32-POE-ISO (where 3.3V output on the UEXT is enabled by default).
#19
A64 / Re: TWI2 (i2c-2) external pull...
Last post by LubOlimex - November 05, 2025, 09:17:48 AMHello mauricio,
Please be more specific. What interface do you want to use exactly (e.g. SPI, TWI/I2C, UART, just GPIO, etc)? Where are you planning to connect your peripheral at the board exactly (e.g. GPIO header, UEXT, etc)?
Not all interfaces require adding anything. For example, if you use TWI1 at UEXT1 header there are already 2.2k pull up resistors placed.
Usually it is best idea first to check the schematic of your exact board revision here:
https://github.com/OLIMEX/OLINUXINO/tree/master/HARDWARE/A64-OLinuXino/2.%20Older%20hardware%20revisions
Please be more specific. What interface do you want to use exactly (e.g. SPI, TWI/I2C, UART, just GPIO, etc)? Where are you planning to connect your peripheral at the board exactly (e.g. GPIO header, UEXT, etc)?
Not all interfaces require adding anything. For example, if you use TWI1 at UEXT1 header there are already 2.2k pull up resistors placed.
Usually it is best idea first to check the schematic of your exact board revision here:
https://github.com/OLIMEX/OLINUXINO/tree/master/HARDWARE/A64-OLinuXino/2.%20Older%20hardware%20revisions
#20
UEXT / Re: ESP32-PoE-ISO-16MB --> MOD...
Last post by swaff - November 04, 2025, 08:17:45 PMThis is the Olimex MOD-BME280. It is connected directly to the MOD-IO via UEXT (no cable). The MOD-IO is connected via an included cable to the Olimex ESP32-PoE-ISO-16MB UEXT port.
The MOD-IO is powered via the jack. I've tried both USB and PoE power to power the ESP32 with no change.
The MOD-BME280 is powered via the UEXT connector as I thought that's how it was supposed to work. And most of the time it does work, but sometimes the humdity reading disappears, and even more rarely I've seen temperature and pressure stop working.
The MOD-IO is powered via the jack. I've tried both USB and PoE power to power the ESP32 with no change.
The MOD-BME280 is powered via the UEXT connector as I thought that's how it was supposed to work. And most of the time it does work, but sometimes the humdity reading disappears, and even more rarely I've seen temperature and pressure stop working.