Real slow atmega328p

Other Hardware 3rd Party Boards
1

I soldered up a prototype board (my first attempt with SMD parts and a hotplate) with an atmega328p-au with a 16mhz resonator and some sensors. I'm pretty sure I pre-loaded an UNO Optiboot bootloader to the 328p. The Arduino IDE seems fine when programming the 328p with the UNO board selected.

Unfortunately I no longer have access to the miso/mosi pins, just rx/tx, etc for loading sketches via FTDI.

Anyways, the sketches I run are responding VERY slowly, about 1 mhz apposed to 100 mhz with a breadboarded prototype.

Is there a way to determine what speed the processor is running at? I'm thinking I may have a fuse problem and the internal clock/divide 8 may be occuring. Anything else may be causing the large slow-down?

2

16 MHz? (Large M for Mega, small m for milli)
Write a sketch that flashes an LED once a second.
If it takes longer, then likely the internal 8 MHz oscillator is selected, and/or the /8 prescaler is selected, or ...
Sure sounds like a fuse setting problem.
You can't make an adapter to let you connect up to an AVR ISP? Even just tacking some wires on temporarily out to a 6 pin header?

3

Thanks Crossroads. I think I can tack on some wires and check fuses that way, but was hoping to avoid that.

Is it odd that the Arduino IDE programs without complaint if the fuses may not be right?

4

If you go under File:Preferences and check the Verbose boxes, do you see any errors when it downloads?

5

No errors uploading sketches, but found this in the verbose messages...

The slow 328p:
Vtarget : 0.3 V
Varef : 0.3 V
Oscillator : 28.800 kHz
SCK period : 3.3 us

A regular 328p:
Vtarget : 0.0 V
Varef : 0.0 V
Oscillator : Off
SCK period : 0.1 us

I got the above by uploading a little sketch to the slow and to a regular 328p and comparing the messages.

I'm guessing my fuses are set wrong on the slow 328p or the 16Mhz resonator isn't soldered well(?).

I'll try to wire up the MISO/MOSI pins and try to check the fuses for sure that way.

Sure would be nice if AVRDude would message out the fuse settings when uploading sketches.

6

Are you sure it says 28kHz?

The 328 has an option for 128kHz internal oscillator. It runs very slowly with that.

OTOH if the bootloader is working then it suggests you're running at 16MHz.

7

The 28kHz was copy/pasted from the Arduino IDE messages.

I'm confused about what's going on. I was playing with a LilyPad bootloader and that may possible what's on the 328p. But why Arduino IDE loads sketches with the UNO board selected in this case is strange.

Hope to get to the bottom of this once I can get the fuses read and bootloader identified.

8

slachowiec:
I'm confused about what's going on. I was playing with a LilyPad bootloader and that may possible what's on the 328p. But why Arduino IDE loads sketches with the UNO board selected in this case is strange.

The IDE board selection only selects chip and serial baud rate. It doesn't know what PCB is actually attached.

9

Ignore those strange figures. In order to save space the optiboot bootloader doesn't implement code to report those values. instead it just sends an empty response.