I just wired a Moteino into a fairly simple circuit, driving a short (12 led) length of Neopixel strip. (This should draw negligible current until given a drive signal).
It uses:
- 5v USB power (although the problem exhibits without this, see below)
- a 100uF capacitor across 5v in - GND
If I connect the FTDI board, I can load a sketch and it will run.
If I connect the FTDI to the USB and don't load a sketch (and hence send a reset), then nothing happens - no D13 Led, no sketch
However, if I reset the hub connected to the FTDI board, the loaded sketch will then run.
I'm thinking two things could be happening:
- the reset timing is wrong and the AVR isn't getting a reset on powerup - maybe because the power line isn't rising quickly enough compared to RESET.
- the serial port is picking up noise during startup and hanging the boot sequence
My next step is was to try manually shorting RESET to GND and see if that starts the bootloader/sketch.
It did. So it must be a lack of power-on reset. Maybe I should either ground FTDI pin 6 when the FTDI isn't in use, or play with the watchdog settings?
I was just wondering if this was a known problem at all?
Thanks,
Richard
Quote from: richdrich on September 03, 2015, 09:54:35 PM
My next step is was to try manually shorting RESET to GND and see if that starts the bootloader/sketch.
It did. So it must be a lack of power-on reset. Maybe I should either ground FTDI pin 6 when the FTDI isn't in use, or play with the watchdog settings?
I was just wondering if this was a known problem at all?
I routinely ground FTDI pin 6 when not using the cable. Depending on your power source, this may be necessary - I have found it so in several cases.
Tom
Yep, thanks!
Grounding FTDI.6 works, 100n between reset and ground does not - well, it makes the device boot, but stops the FTDI reset input working, so you can't program it.