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#21
A20 / HDMI connection back feeding i...
Last post by dry - March 03, 2026, 02:30:05 PMI noticed that red power led is on on A20-CAN board which I plugged into the GPIO3 on the A20 micro board, even though power was not connected.
After disconnecting all but HDMI, then removing it, i saw red led going off. I measure about 1.8V on VDD1 tp and 1V on VREF test points on that CAN extension board, and I measure bout 1.8V on the 5V pin on GPIO 1 connector on A20 micro board.
So is this back-feeding a problem for overall usage, will I get any weird gremlins?
(Perhaps unrelated, but I noticed that ethernet may not be found on some boots..)
After disconnecting all but HDMI, then removing it, i saw red led going off. I measure about 1.8V on VDD1 tp and 1V on VREF test points on that CAN extension board, and I measure bout 1.8V on the 5V pin on GPIO 1 connector on A20 micro board.
So is this back-feeding a problem for overall usage, will I get any weird gremlins?
(Perhaps unrelated, but I noticed that ethernet may not be found on some boots..)
#22
ESP32 / Re: New ESP32-POE-ISO - was I ...
Last post by LubOlimex - March 03, 2026, 09:21:41 AMUmm, you have to measure between pin 1 and pin 3 (GND and VIN). Write down the measurement that goes in. It should be around 4.6V.
Then measure between pin pin 1 and pin 2 (GND and SW). Write down the measurement that goes out. It should be 3.10V-3.20V.
Instead of using pin 1 for GND, for easier time measuring you can use any other GND, for example the pad of EXT1 header.
It is a bit tricky since U7 is small and pin 2 and pin 3 are next to each other at the side of the EXT1 header but I did it today so it is doable.
Then measure between pin pin 1 and pin 2 (GND and SW). Write down the measurement that goes out. It should be 3.10V-3.20V.
Instead of using pin 1 for GND, for easier time measuring you can use any other GND, for example the pad of EXT1 header.
It is a bit tricky since U7 is small and pin 2 and pin 3 are next to each other at the side of the EXT1 header but I did it today so it is doable.
#23
PIC / Re: PIC-USB-4550 program does ...
Last post by LubOlimex - March 02, 2026, 04:48:39 PMUmm wrong compiler for that code. You need PIC18 compiler in LITE mode:
https://www.microchip.com/en-us/development-tool/sw006011
It is free to download just requires registration.
https://www.microchip.com/en-us/development-tool/sw006011
It is free to download just requires registration.
#24
PIC / Re: PIC-USB-4550 program does ...
Last post by emil_bbb - March 01, 2026, 10:37:42 PMI have also tried to compile the program in MPLAB X IDE v6.25 but I get error messages.
make -f nbproject/Makefile-default.mk SUBPROJECTS= .build-conf
make -f nbproject/Makefile-default.mk dist/default/production/Bootloader.X.a
make[2]: Entering directory 'C:/Users/Emil.BC/MPLABXProjects/Bootloader.X'
"C:\Program Files\Microchip\xc8\v3.10\bin\xc8-cc.exe" -mcpu=18F4550 -c -mdfp="C:/Program Files/Microchip/MPLABX/v6.25/packs/Microchip/PIC18Fxxxx_DFP/1.7.171/xc8" -memi=wordwrite -O0 -fasmfile -maddrqual=ignore -xassembler-with-cpp -mwarn=-3 -Wa,-a -DXPRJ_default=default -msummary=-psect,-class,+mem,-hex,-file -ginhx32 -Wl,--data-init -mno-keep-startup -mno-download -mno-default-config-bits -std=c99 -gdwarf-3 -mstack=compiled:auto:auto:auto -o build/default/production/bootloader.p1 bootloader.c
In file included from bootloader.c:6:
C:/Program Files/Microchip/MPLABX/v6.25/packs/Microchip/PIC18Fxxxx_DFP/1.7.171/xc8\pic\include\proc/pic18f4550.h:41:2: warning: Header file pic18f4550.h included directly. Use #include <xc.h> instead. [-W#warnings]
41 | #warning Header file pic18f4550.h included directly. Use #include <xc.h> instead.
| ^
bootloader.c:22:5: error: use of undeclared identifier '_asm'
22 | _asm goto _startup _endasm
| ^
1 warning and 1 error generated.
make[2]: Leaving directory 'C:/Users/Emil.BC/MPLABXProjects/Bootloader.X'
make[2]: *** [nbproject/Makefile-default.mk:104: build/default/production/bootloader.p1] Error 1
make[1]: *** [nbproject/Makefile-default.mk:85: .build-conf] Error 2
make: *** [nbproject/Makefile-impl.mk:39: .build-impl] Error 2
BUILD FAILED (exit value 2, total time: 1s)
I find it impossible to load a working programm in the pic
Is there any other programm that works with the bootloader, other than the blinking led?
make -f nbproject/Makefile-default.mk SUBPROJECTS= .build-conf
make -f nbproject/Makefile-default.mk dist/default/production/Bootloader.X.a
make[2]: Entering directory 'C:/Users/Emil.BC/MPLABXProjects/Bootloader.X'
"C:\Program Files\Microchip\xc8\v3.10\bin\xc8-cc.exe" -mcpu=18F4550 -c -mdfp="C:/Program Files/Microchip/MPLABX/v6.25/packs/Microchip/PIC18Fxxxx_DFP/1.7.171/xc8" -memi=wordwrite -O0 -fasmfile -maddrqual=ignore -xassembler-with-cpp -mwarn=-3 -Wa,-a -DXPRJ_default=default -msummary=-psect,-class,+mem,-hex,-file -ginhx32 -Wl,--data-init -mno-keep-startup -mno-download -mno-default-config-bits -std=c99 -gdwarf-3 -mstack=compiled:auto:auto:auto -o build/default/production/bootloader.p1 bootloader.c
In file included from bootloader.c:6:
C:/Program Files/Microchip/MPLABX/v6.25/packs/Microchip/PIC18Fxxxx_DFP/1.7.171/xc8\pic\include\proc/pic18f4550.h:41:2: warning: Header file pic18f4550.h included directly. Use #include <xc.h> instead. [-W#warnings]
41 | #warning Header file pic18f4550.h included directly. Use #include <xc.h> instead.
| ^
bootloader.c:22:5: error: use of undeclared identifier '_asm'
22 | _asm goto _startup _endasm
| ^
1 warning and 1 error generated.
make[2]: Leaving directory 'C:/Users/Emil.BC/MPLABXProjects/Bootloader.X'
make[2]: *** [nbproject/Makefile-default.mk:104: build/default/production/bootloader.p1] Error 1
make[1]: *** [nbproject/Makefile-default.mk:85: .build-conf] Error 2
make: *** [nbproject/Makefile-impl.mk:39: .build-impl] Error 2
BUILD FAILED (exit value 2, total time: 1s)
I find it impossible to load a working programm in the pic
Is there any other programm that works with the bootloader, other than the blinking led?
#25
ESP32 / Re: New ESP32-POE-ISO - was I ...
Last post by chrismacp - March 01, 2026, 12:29:42 AMI'm wondering, before I start trying to solder anything. Are there any measurements I could take to confirm where the problem is. I'm most definitely an amateur at this stuff currently so trying to learn where I can.
I measured ~1.9v across pin 1 (GND) and pin 6 (Out according to datasheet although just 'x' in the Kicad file) of U7 when there is 5v applied to the 5v pin of the microcontroller board. It's ~1.4v when usb power is connected.
I'm not sure if that helps to figure out if the component is broken or not.
I measured ~1.9v across pin 1 (GND) and pin 6 (Out according to datasheet although just 'x' in the Kicad file) of U7 when there is 5v applied to the 5v pin of the microcontroller board. It's ~1.4v when usb power is connected.
I'm not sure if that helps to figure out if the component is broken or not.
#26
ST / Re: BB-STM32WL and Platformio/...
Last post by LubOlimex - February 27, 2026, 08:41:49 AMI think you are correct. It seems the ESP-PROG design was made only for ESP boot sequence. I will add it as a note on the product page. Maybe jut use regular general-purpose USB-serial cable. Like:
https://www.olimex.com/Products/USB-Modules/Interfaces/USB-SERIAL-L/
USB-SERIAL-L does not internally couple RTS and CTS. But you must wire it properly and probably put like 1k resistor between RTS and boards RESET and between CTS and BOOT0.
https://www.olimex.com/Products/USB-Modules/Interfaces/USB-SERIAL-L/
USB-SERIAL-L does not internally couple RTS and CTS. But you must wire it properly and probably put like 1k resistor between RTS and boards RESET and between CTS and BOOT0.
#27
ESP32 / Re: What board should I use?
Last post by LubOlimex - February 27, 2026, 08:22:57 AMOf course, PoE is optional. You can still power them from USB or external power supply and have a back-up Li-Po battery. The Ethernet is fully functional as long as the board is powered.
Notice that you can stack more than one MOD-IO board, just change the I2C address of the second, the third, and so on.
Notice that you can stack more than one MOD-IO board, just change the I2C address of the second, the third, and so on.
#28
ST / Re: BB-STM32WL and Platformio/...
Last post by winfried - February 26, 2026, 04:42:05 PMWorkin manual: the sequence is with buttons to GND:
BOOT0 -> low (button closed)
RESET -> low (button closed)
RESET -> high (button released)
BOOT0 -> high (button released)
--
To understand the Transistor Logic in ESP-PROG it did, thanks to KiCAD, a fast simulation on /RTS and /DTR to DCOM and EN see picture below:
It seems, there is no combination of both signals being low at the same time, so it does not work, or am I wrong ?
BOOT0 -> low (button closed)
RESET -> low (button closed)
RESET -> high (button released)
BOOT0 -> high (button released)
--
To understand the Transistor Logic in ESP-PROG it did, thanks to KiCAD, a fast simulation on /RTS and /DTR to DCOM and EN see picture below:
It seems, there is no combination of both signals being low at the same time, so it does not work, or am I wrong ?
#29
ESP32 / Re: What board should I use?
Last post by fredy - February 26, 2026, 02:58:02 PMHi!!
Thanks for response and your advise!
Last question: could I use POE boards without use the power of POE and use the ethernet to send data?
Thanks in advance!
Thanks for response and your advise!
Last question: could I use POE boards without use the power of POE and use the ethernet to send data?
Thanks in advance!
#30
ST / Re: BB-STM32WL and Platformio/...
Last post by LubOlimex - February 26, 2026, 08:31:29 AMHmmm, you might need oscilloscope for this one. I think the problem comes from ESP-PROG logic that is made for ESP auto-boot and STM32 boot logic is possibly different. Maybe try with
I think to enter STM32 system bootloader:
BOOT0 = HIGH
RESET = LOW
wait ~100 ms
RESET = HIGH
BOOT0 can stay HIGH (or go LOW after reset)
To exit bootloader:
BOOT0 = LOW
RESET pulse again
If it does not work, the signals may be inverted on your ESP-PROG. In that case, swap rts with -rts and dtr with -dtr. If possible, verify with a multimeter or oscilloscope that:
EN actually goes LOW during reset and BOOT0 actually goes HIGH during boot. That will show whether inversion is the issue.
Code Select
-i '-rts,,-dtr,100,dtr:,-rts'Code Select
upload_flags = -R -i '-rts,,-dtr,100,dtr:,-rts'I think to enter STM32 system bootloader:
BOOT0 = HIGH
RESET = LOW
wait ~100 ms
RESET = HIGH
BOOT0 can stay HIGH (or go LOW after reset)
To exit bootloader:
BOOT0 = LOW
RESET pulse again
If it does not work, the signals may be inverted on your ESP-PROG. In that case, swap rts with -rts and dtr with -dtr. If possible, verify with a multimeter or oscilloscope that:
EN actually goes LOW during reset and BOOT0 actually goes HIGH during boot. That will show whether inversion is the issue.