We have a cadence/pace sensor for a bike, and we want to retrieve the "sin" by plugging it to a GPIO Pin of a Raspberry PI. The signal "sin" has a voltage that varies between 0 and 5V. We used a 2/3 dividing bridge to lower the max voltage to 3.3. Everything works, but when plugging the "sin" onto the GPIO Pin the max voltage value drops to around 0.5-0.9V. We've tried a lot of different things and the voltage always drops...

This stops us from measuring a high tick since the voltage for a GPIO Pin's logical high is 1.8V.

Edit : The problem with our sensor is that it's a Chinese rip off. Therefore we have little to none information about it. Our assumptions were the following concerning how the sensor works : The "sin" input in the RPI corresponds to the sinus output of our pace. Basically what we understood is that our pace meter has 18 slots all around its wheel, and every time the wheel rotates it outputs a "high" value voltage whenever it goes through one of these slots. To measure the RPM we measure the tick difference it takes for 18 rising edges to happen thus giving us the time it took for a whole rotation. With the pace output unplugged, a high value output hovers at 4.30V but when plugged to the RPI it falls to 0.5-0.9V

Concerning the 2/3 dividing bridge, we tried using very high resistance values (330 - 700k Ohms) as well as low values (330 Ohms) and it changed nothing. The current values were always at around 2 - 0.5mA which is below RPI limit.

We have a cadence/pace sensor for a bike, and we want to retrieve the "sin" by plugging it to a GPIO Pin of a Raspberry PI. The signal "sin" has a voltage that varies between 0 and 5V. We used a 2/3 dividing bridge to lower the max voltage to 3.3. Everything works, but when plugging the "sin" onto the GPIO Pin the max voltage value drops to around 0.5  - 0.9V. We've tried a lot of different things and the voltage always drops...

This stops us from measuring a high tick since the voltage for a GPIO Pin's logical high is 1.8V.

Edit : The problem with our sensor is that it's a Chinese rip off. Therefore we have little to none information about it. Our assumptions were the following concerning how the sensor works :

The "sin" input in the RPI corresponds to the sinus output of our pace. Basically what we understood is that our pace meter has 18 slots all around its wheel, and every time the wheel rotates it outputs a "high" value voltage whenever it goes through one of these slots. To measure the RPM we measure the tick difference it takes for 18 rising edges to happen thus giving us the time it took for a whole rotation. With the pace output unplugged, a high value output hovers at 4.30V but when plugged to the RPI it falls to 0.5  - 0.9V

Concerning the 2/3 dividing bridge, we tried using very high resistance values (330 - 700k ohms) as well as low values (330 ohms) and it changed nothing. The current values were always at around 2 - 0.5mA which is below RPI limit.

We have a cadence/pace sensor for a bike, and we want to retrieve the "sin" by plugging it to a GPIO Pin of a Raspberry PI. The signal "sin" has a voltage that varies between 0 and 5V. We used a 2/3 dividing bridge to lower the max voltage to 3.3. Everything works, but when plugging the "sin" onto the GPIO Pin the max voltage value drops to around 0.5-0.9V. We've tried a lot of different things and the voltage always drops...

This stops us from measuring a high tick since the voltage for a GPIO Pin's logical high is 1.8V.

We have a cadence/pace sensor for a bike, and we want to retrieve the "sin" by plugging it to a GPIO Pin of a Raspberry PI. The signal "sin" has a voltage that varies between 0 and 5V. We used a 2/3 dividing bridge to lower the max voltage to 3.3. Everything works, but when plugging the "sin" onto the GPIO Pin the max voltage value drops to around 0.5-0.9V. We've tried a lot of different things and the voltage always drops...

This stops us from measuring a high tick since the voltage for a GPIO Pin's logical high is 1.8V.

Edit : The problem with our sensor is that it's a Chinese rip off. Therefore we have little to none information about it. Our assumptions were the following concerning how the sensor works : The "sin" input in the RPI corresponds to the sinus output of our pace. Basically what we understood is that our pace meter has 18 slots all around its wheel, and every time the wheel rotates it outputs a "high" value voltage whenever it goes through one of these slots. To measure the RPM we measure the tick difference it takes for 18 rising edges to happen thus giving us the time it took for a whole rotation. With the pace output unplugged, a high value output hovers at 4.30V but when plugged to the RPI it falls to 0.5-0.9V

Concerning the 2/3 dividing bridge, we tried using very high resistance values (330 - 700k Ohms) as well as low values (330 Ohms) and it changed nothing. The current values were always at around 2 - 0.5mA which is below RPI limit.