In my keyboard, I am using a mdbt40-256rv3 bluetooth module desoldered from a Bluefruit SPI friend flashed with BLESPIFRIEND 0.6.7. I am certain that my PCB is correct, as I have been using this design for the past two years with no problems. I just had to solder a new module onto a different PCB (after the old one broke) and I run into the following weird behaviours:
- The module boots into DFU mode at random. Otherwise, the red LED flashes to indicate it's in DFU mode, and holding the DFU pin low to perform a factory reset does not seem to do anything.
- DFU mode works as expected -- I can connect with the Bluefruit Connect App and flash firmware.
- As of minutes ago (after I reflashed the firmware with DFU), when not in DFU mode, the connection LED is blinking irregularly (even when connected) , and I had trouble pairing to some devices. DFU mode still works alright (even when I don't want to be in DFU mode) and connection LED works properly there.
- I also tried flashing to the latest version (0.8.1) but still observe the same behaviours.
I verified that there are no shorts, that the DFU pin (P0.07 / Pin 7) is not connected to GND, and even soldered a 10k pull-up to 3.3v. I also checked that all other pins are connected where they should be. I wonder if anyone at Adafruit has experienced this when working with the Bluefruit SPI Friends / BLE Feathers. I did not do my part to test the module before transferring it to my own board, but I highly doubt that it was broken in the first place. Could it be that the heat damaged it in a certain way?
Intermittent booting into DFU mode -- Bluefruit SPI friend
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- hristo.staykov
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- Franklin97355
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Re: Intermittent booting into DFU mode -- Bluefruit SPI frie
Can you post pictures of the module and your PCB? If you include a schematic of you board it would also be helpful.
- hristo.staykov
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Re: Intermittent booting into DFU mode -- Bluefruit SPI frie
@franklin97355 sure, here are some photos of my PCB (splitting this in multiple posts because there's an upload limit):
- hristo.staykov
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Re: Intermittent booting into DFU mode -- Bluefruit SPI frie
Photos of PCB, contd:
https://github.com/hristost/merp-pcb.
I believe that the connection LED blinking is an indication of the board attempting to do a factory reset due to it thinking the DFU pin is low. Once connected to a computer, it's lit all the time.
The PCB itself is based on the schematic for the 32u4 Feather BLE:
The full schematic is available / pcb at I believe that the connection LED blinking is an indication of the board attempting to do a factory reset due to it thinking the DFU pin is low. Once connected to a computer, it's lit all the time.
- hristo.staykov
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- Joined: Thu May 09, 2013 3:06 pm
Re: Intermittent booting into DFU mode -- Bluefruit SPI frie
I also measured the voltage at the DFU pin -- it's around 1.5V, which is a HIGH? If I recall correctly, the module runs on 1.8V internally.
Please be positive and constructive with your questions and comments.