Joe,
You've definitely got your S-Meter requirements taken care of.? ;-)
And would indeed be a shame to waste those dual SPI displays on a Nano.
Let us know what feels right in a final radio and what is stuff you maybe didn't need.
There's a wide range of STM32F parts available, different amounts of memory, ADC speeds and type, FPU.
Access to that in? pin compatible packages is worth a buck.
Quality and some details (is USB bootloader in flash?? which pin is the LED tied to?? does it work at all?)
on a $2 BluePill can vary considerably.? Pretty much zero glue needed except LED's and R's and a voltage regulator.
I'd prefer something other than an 8mhz resonator on the processor.
We're seeing trouble with the Nano's where the 16mhz and 12mhz resonators can sometimes choose
to be of a frequency where fundamental or harmonics of?that and the BFO create audio tones that are hard to kill.
When that happens, best bet is to clip out the Nano and try a different one as those resonators are dinky.
Likewise, I'd just as soon not have a USB interface running while using the radio, I'm fine with something like this
to program the firmware via the bootloader in ROM using a UART interface from a host USB port:
? ??
That item can be configured for 5v or 3.3v io to the Arduino.
It's much easier to choke out any RF from those 9600 baud UART lines than it is to clean
up a 12mhz USB interface, and sometimes we will want that running while operating the radio.
Jerry
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On Fri, May 18, 2018 at 08:12 am, W3JDR wrote:
BTW, I considered starting out at the STM chip level, but you can buy the whole board cheaper than you can buy the chip. And you'd have to put all the necessary 'glue' around it and then build it and burn an Arduino compatible bootloader into it. Also, an FPU is primarily useful in DSP applications, and I see that as being a separate unit, so I'm going the Pill route.
