johnlinford

Just by way of a thread conclusion, I've now breadboarded the replacement Teensy 4.0 and 74LS07 and everything is working as expected. That's the better part of a day spent chasing a non existent design fault but got there in the end and learned...

D'oh! How did I miss that? 10mA eh... that's more than enough!

I have to offer profound apologies! I broke out a brand new T4.0, soldered some legs on it and ran the above test with a 1k0 resistor first to 3V3 and then to ground. Both tests were fine, with a nice rail-to-rail square wave. Went back to the...

Good test plan Mark. I tried multiple analogue outputs, pulling them up to 3V3 and down to Gnd with various resistor values as I watched the 2kHz square wave on my oscilloscope. In all cases a 1k0 resistor in either direction results in the pin...

Thanks, @jmarsh. I'm driving the pin (and others) with square wave signals derived from a 2kHz timer interrupt and I can clearly see the square wave on the Teensy pin with my oscilloscope. When the 74LS07 gate is attached the square wave range is...

Well I am referring to them as analogue pins because that's what they are called in the documentation (A0, A1...) and they are able to receive analogue input and send PWM output. The code is really rather straightforward and yes, I have set...

Oh, I hadn't thought of that. No I use digitalWrite(p, LOW); as I simply want an active LOW output. The analogue pin goes LOW OK with no load but only gets down to about 1.2V with the 74LS07 gate attached. The 74LS07 gate inputs are...

I'm tinkering with a project that (just) fits onto a Teensy 4.0 in terms of I/O capacity but virtually all the I/O is digital output including the analogue ports. Typically I am driving a single SN74LS07 input and I'm finding that the Teensy...

I wasn't aware of the RV-3028-C7 but it looks like an interesting device and I can certainly think of applications where it would be useful. Thanks! Thanks everyone for all the external RTC source suggestions but TBH I was rather hoping to learn...

I had forgotten about MSF et al! Yes that would work, especially as the 60kHz MSF transmitter is just down the road from me. Years ago I designed a clock based on MSF and it worked well, though the data rate is so low that it takes a full minute...

I did think about GNSS and have used it in other designs, it would be more than adequate. In the end it may be the only realistic way to get the sort of accuracy I am after. I was just hoping I could avoid the additional complexity and the risk...

Yes, I realise that it's not bad for a non-temperature compensated crystal oscillator - I think the spec is something like 20ppm. Ideally I'd like to get to around 1ppm. I can easily compute the RTC drift over time, so perhaps another possibility...

My first post on this forum, thank you for having me here! I've been using Teenys in my projects for several years with great results and they are my go-to SBC for nearly all my designs. I have a current Teensy 4.1 project that requires accurate...