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1st board assembled
06/16/2018 at 05:44 • 0 commentsthe title says everything.
I had some difficulties hitting the right combination of resistors for the opamp. I guess Vref in the opamp circuit should have come from a voltage reference rather a simple voltage divider, and also I should have paid more attention to and money for the resistors in the PSU-section as ±4.65 is more like + 4.660V / -4.365V.
But everything turned out well in the end. Output from the CCD now looks like this:
rather than this:
Improvements in noise is probably from setting the scope to 12-bits instead of 10, but the interesting part is that the output for zero light is 145mV, and a full saturation is 3.23 V. Fairly close to the boundaries of the ADC's range.
Next up is porting the firmware for the STM32F401 to the STM32F405 and redirecting communication to USB. The first part willl be easy, I'm less certain about the USB-part, but I've completed the first step: Getting the MCU recognized as virtual com port (ttyACM) on my laptop.
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Boards
05/25/2018 at 13:41 • 0 commentsThe PCBs have finally arrived and after a few trial runs/failures with 0603, there's this:
Opamps are still not fitted, and there was an error in the circuit around the switches.
The PSU-sections work, and when the Dfu bootloader runs the MCU is identified correctly by my laptop, and the LED blinks. In short everything seems to work.
I "just" have to figure out how to setup the chip as a virtual com port.