It's still not clear to me what you have, how this trigger and sine-wave relates to a falling edge, how this 0.8V comes into play, but, if you are reading what you expect at low frequencies but not higher it suggests to me it is a time delay between the PicoMite detecting a trigger and reading the ADC.I aim for the signals measured by the 16 ADCs (across 4 PICO units, each with 4 ADC channels) to be below 0.8 V, as the trigger is set to the falling edge. At a lower frequency of 30 Hz, I observed voltages of 0.804 V and 0.811 V. However, as I increase the frequency, the voltage continues to rise, as detailed in the previously shared PDF file.
PicoMite Basic is an interpreter. If it's interpreting source code, tokenised code, even bytecode, it may be much slower than expected.
When the frequency is low the wave period is long enough that it probably hasn't risen above the trigger level when ADC is read -
Code:
____ ____ __--- ---__ __--- ---__Sine Wave -- --__ __-- --__ __-- ---____--- ---____--- : : : : : : : :Trigger ____________________|_______:_______________________|_______:_____ : :Read ADC ____________________________|_______________________________|_____ | Delay | | Delay |Code:
__ __ __ _-- --_ _-- --_ _-- --_ _-Sine Wave _ _- -_ _-: -_ _-: -_ _- --__-- --__-- : --__-- : --__-- : : : : : : : :Trigger ____________________|_______:_________|_______:___________________ : :Read ADC ____________________________|_________________|___________________ | Delay | | Delay |As suggested; present a pulse on a GPIO pin then you can see what's shown above on a scope. That should allow you to see exactly when ADC is being read, what the delay is between the trigger and the ADC read.
I don't know how deterministic PicoMite Basic is. If it doesn't have hard interrupts which are immediately responded to, merely notes the interrupt and schedules the interrupt handler at the end of the command line being executed, there could be indeterminate delays.I plan to utilize this setup later for data acquisition from equipment where precision is paramount, and any deviation could compromise the results.
That might even explain any delays which are being seen. Generating a pulse when ADC is read should reveal whether the delay from trigger is consistent or not.
Statistics: Posted by hippy — Sat Aug 03, 2024 3:50 pm