75 Resistor Capacitor TDC

75 : Resistor Capacitor TDC

Design render
  • Author: Rowan Tyler
  • Description: Calculated the resistance of an external RC circuit based on its measured rise time to an outputted step signal
  • GitHub repository
  • Open in 3D viewer
  • Clock: 50000000 Hz

How it works

A way of estimating resistance for external sensors without a mixed signal ADC. Excites an external RC cicuit with a step, and measures the time taken for the circuit to rise. This rise is assumed to be when input digital pin that is connected to the analogue RC rising voltage flips from 0 to 1. Uses this time to calculate resistance.

How to test

First pulse the reset high, then once the circuit is enabled, will output step voltage, measure time for step input to be seen and then will output 32 bit calculated resistance value via the uart pin.

External hardware

Only require a resistor and 10 nF capacitor.

IO

#InputOutputBidirectional
0reset_instep_set
1enableuart_tx
2step_input
3
4
5
6
7

Chip location

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