开云体育

Rev 3 is not here yet. The cargo cleared customs today in Izmir so I expect the last 250km by road to take 2-3 days. The changes from Rev 2 -> Rev 3 are minor, as follows:

This was just because there was a very occasional tendency for a solder bridge to occur here.?

After this change, the?microcontroller GPIO port PB4 (pin 90) never sees more than?+5V. Previously it saw the full supply voltage e.g. +12V via 100K resistor R209. Technically this probably exceeds the GPIO pin specification, arguably, depending on how you interpret the datasheet. There is no reported instance of any damage or failure which could be causally linked to this. However, just for the sake of good practice, I made the change to connect the Q202? source to?+5V instead of?+12V. Circuit?operation is unaltered by this but it avoids the potential specification breach.?

This is similar to point 2, above. Now on GPIO port pin PD7 (pin 88) which could also see the full?+12V supply?via a 100K resistor. Again no known instance of any failures can be causally linked to this potential breach but for good practice, it is prudent to avoid it. So I added a new 100K resistor R115 from LIN_REG_EN to Gnd. That ensures that the voltage at this GPIO pin is halved, so it doesn't exceed 6V. Yet it does not affect the functionality of the supply switchover circuit from linear to SMPS buck converters.?

This can potentially provide a greater degree of protection against voltage spikes in the millisecond interval that it takes the SMPS buck converter control loop to counter any increases in supply voltage. Note that this has already effectively been 5W for several hundred kits already?because the SMPS boards were also manufactured and sold separately.?

It's also a very long story - that did cause several weeks of pain here - the 3.6V zener in the 3.3V supply was also changed to a 5W type. But who knew, you just can't do that. Briefly: zener diodes below 5V have a very very shallow action. There are two mechanisms, the zener break-down and avalanche breakdown. Below 5V or so, the zener break-down is dominant and it is very gradual indeed. A diode specification includes the current at which the voltage measurement is made. If you intend to operate at any other current, you better beware, the voltage will be totally different! This was all new to me and I had to do a great deal of experimentation to unravel it, then we obtained 500 3.6V 500mW diodes again and had to swap out all the 5W diodes on the separately made SMPS boards. That's why you see a red glass diode on some boards.?

Just an attempt to get better soldering of the USB-C connector.?

This modification was already made, by us, to all Rev 2 boards shipped as kits and assembled radios.?

The modification required to Rev 2 boards, described here:?

Which has already been made, by us, to all Rev 2 boards shipped as kit or assembled radio, from the start of 2024.?

Just to tidy up and make the component naming consistent!