Computing stuff tied to the physical world

Getting ready for OptiBoot 4.4

In AVR, Hardware, Software on Jan 7, 2012 at 00:01

Ok, it’s official – starting this week, all new ATmega’s here will be flashed with the OptiBoot 4.4 boot loader.

It’s going to take a while for all current inventory units to “flush through the system” so to speak (both DIPs and SMDs), but at some point this month all ATmega’s will be running the same boot loader as the Arduino Uno. Faster, smaller, and – hopefully – no more troubles with Windows being unable to upload sketches through FTDI.

One of the things I’ve done is to turn one of the new JeeNode Blocks into a dedicated Portable ISP Programmer for DIP-28′s. It’s the same isp_repair2 sketch as before (modified for the Block’s minor pin allocation diff’s):

DSC 2847

Note the 16 MHz resonator behind the ZIF socket. Here’s the wiring:

DSC 2848

There’s no 10 kΩ pull-up resistor for RESET, because ATmega’s have a (weak) built-in pull-up.

To avoid the delay-on-hardware-reset, I’ve added a push-button which briefly shorts +3V and GND together through a 10 µF electrolytic cap. Enough to force the JeeNode Block into a hardware reset. There’s a 10 kΩ resistor across the cap to discharge it afterwards. This is really quick because the reset occurs on button press i.s.o. release.

The savings are minimal – just 1..2 seconds more for the standard bootstrap – but for production, it matters. Total flash time, including boot loader, RF12demo sketch, and setting all the fuses is now just a few seconds:

  • insert DIP chip
  • close ZIF socket
  • press button
  • wait for two LED blinks
  • open ZIP socket
  • remove programmed chip
  • rinse and repeat…

When a serial port is connected via FTDI, you can see the progress of it all:

Screen Shot 2012 01 04 at 20 01 42

Now let’s just hope that this version of OptiBoot doesn’t lead to the same mess as the previous one.

If you have older JeeNodes or other ATmega328 boards running previous bootstrap loaders, I suggest looking at the recent ISP programmer post and the older summary. You might consider bringing all units up to date, because with a mix of boot loaders you end up constantly using the wrong one in the IDE and having to adjust board types each time.

Just be careful when messing with boot loaders. If the process goes wrong and you pick the wrong fuse settings, then you can end up with a “bricked” unit (only a high-voltage programmer can recover from such a state).

But apart from that: enjoy the doubled 115.2 Kbaud upload speed and the 1.5 Kb extra space for sketches!

  1. You can use an arduino and a few small parts as a high-voltage programmer.

  2. Having the same bootloader on all devices sure makes programming more uniform, but tbh, i ran into a situation where having different ones was a good thing: i have one Linknode (to send commands via rf12) and one Jeenode & breadboard hooked up to the same laptop. They show up as com3 & com4. When i tried to send a new program to the Jeenode i had selected the wrong com port, but fortunately it wouldnt upload due to those different bootloaders. Maybe there is a way to “write protect” the linknode in a way that would need some extra step before uploading a new sketch… cu, Neo

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