The Sinclair QL Forum

I couldn't see the resistor label without my loupe, which I couldn't find in the tool box, so I measured it, exactly 1.5K. Later, when I found my loupe, I could read "152", so that matches fine for 1.5K. I suspect because the Blue Pills were German made, they have the fix. It works fine anyway with a mildly amended "blink" sketch. Time to start learning.

Oh yes, I inadvertently downloaded the User Manual for the processor. 1,114 pages. Yikes! (And not as nice to read as the Atmel stuff!)

Cheers,
Norm.

Pi4 power control board and SATA board.




Self explanatory really


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mk79 wrote:....Have fun!

Ha! The fun has started, digitalWrite(LED_BUILTIN, HIGH) turns the built in LED off but an "external" LED connected to the same pin, PC13, turns on!

A quick check of the schematic explains. The built in LED is connected to 3V3 so it must only light up when PC13 goes low. The external LED gets it's 3V3 from the pin, so it will light up when the pin is high. Mystery solved.

I hope you are having as much fun as I am!

Cheers,
Norm

Hi Marcel,

Slightly off topic ......

mk79 wrote:....Have fun!

I wonder if you would do me a favour at your leisure, please. I have those Blue Pill devices from AZ Design in Germany. According to the "Datenblatt" which came with the pills, PC15, PC14 and PC13 are limited to sourcing/sinking 3 mA current. The pinout says sink 3 mA and source 0 mA! The user flashy LED is on PC13 and runs at 3v3.

Looking at R5 on my pills, I see it is marked "681", so 680 Ohms and my multimeter agrees with that value. That's a current of 4.85 mA and exceeds the specs. Even worse, the schematic shows R5 as being only 510 Ohms which I calculate as 6.47 mA or 2.15 times the maximum current allowed. I calculate that R5 should be at least 1.1K to limit the current to the 3 mA in the manual.

If you wouldn't mind, what is the value on your Blue Pill for R5 it's on the bottom of the PCB directly under the user flashy LED. I have a suspicion that all/most of these things might be running a little on the "hot" side.


Cheers,
Norm.

PS. Schmetterlingsflügel is my favourite German word. (From a song by Schiller.)

that 680 ohms doesn't take into account any voltage drop on the LED So you should be ok - as most led's won't light until they dropped at leat 1.5 v which halves your current

Bugger bugger bugger! I always do that! I forget the voltage drop across the LED. I shall write it out 100 times.

That makes it 2.65 mA with my 680R resistors or 3.5 mA with the schematic's 510R resistors.

Thanks Pr0f.


Cheers,
Norm.

NormanDunbar wrote:Bugger bugger bugger! I always do that! I forget the voltage drop across the LED. I shall write it out 100 times.

That makes it 2.65 mA with my 680R resistors or 3.5 mA with the schematic's 510R resistors.

Thanks Pr0f.


Cheers,
Norm.

I think we all forget to do that I get lazy and use an app called electrodroid which has all sorts of useful calculators and pin outs for all sorts of connectors, as well as wire gauges and heatsink calculators and pcb track width calculators....

I've got Electrodroid too! Forgot I had that, I should have used it. Sigh.

Cheers,
Norm.

I'm late to the party, but my boards have the same resistor

Thanks Marcel. The party is still in full swing - socially distanced of course.

Cheers,
Norm