#Pull the pin challenge level 38 software
#Pull the pin challenge level 38 code
#Pull the pin challenge level 38 professional

the interrupt routine fires, notes the time in micros(), and attaches a new interrupt to watch for the end of the pulse.

the sensor does its thing and starts the echo pulse.

attach an interrupt to the pin to watch for the beginning of the echo pulse.

This starts the sensor's ping cycle and turns on the tri-state buffer so the echo state is now visible at the interrupt pi.

Via the I2C expander, drop the trigger pin.

In this high state the tri-state buffer output is at high impedance (off). This is contrary to common practice, but works fine as the sensor is triggered by the falling edge, not by the suggested 10us pulse.

In idle state, the sensor trigger pin is held high.

Wire the outputs of the tri-state buffers to a hardware interrupt pin on the Arduino.

Wire the Echo pins to the inputs of the tri-state buffers.

Also wire them to the control pins of 74HC125 tri-state buffers.

Wire the Trigger pins to PCF8574A expander pins.

The concept behind the OctoSonar library is as follows: I2C bus would be the answer, but the bus itself is not fast enough for accurate echo measurement, and the only reference to an I2C library for these in the playground seemed to be broken.

#Pull the pin challenge level 38 software

It does look as though the software not being maintained anymore and some talk about making it open source but at this point the product works and works very well and for the price right now, its a steal.There are not enough pins on a basic Arduino to provide 2 pins each to 8 HC-SR04 units. Very nice product I think.Ĭan't wait to figure out the other features of this product as I have other signal I need to break down. The display software is quite nice as well and for looking at my WS2812b signal it was simple and easy to do. It also came with the PropScope DAC card which I was not expecting.

#Pull the pin challenge level 38 professional

Professional style probes and not just one but two. I decided it's time to pull the trigger and see what I get.Īgain I was impressed with what I got. To my surprise it went on sale and then on sale. So I put it on my wish list as a item I wanted but thought I will site on it a while. After looking at the schematic I see it was using some hardware to do the sampling and the Propeller to do the interfacing. Hey, that is pretty good for a unit based on the Propeller chip. I then took a closer look at the maximum sample rate which is said was up to 25Mhz. I then took a second look at the PropScope which I thought at the time was a little pricey begin it was USB attached. I was not going to spend the $1,000 price tag for a real scope which would kill my budget and not site well with my wife either. I then set my sites on a faster scope and notice that most of them stopped at the 1Mhz sample range.

#Pull the pin challenge level 38 code

I had to do a little fixing of the code at that higher speed. I then upped the frequency of the code to drive the LED's. I ended up writing slower code that was 100 times slower so that I could use my DSO138 to see the signal. Its maximum sample rate stops at 1 Million sample per second. It appears that a frequency that high is not going to work on this $20 scope. So I setout to write some assembly code to drive the pin fast enough to drive the WS2812b when I notice that my DSO138 scope was not up to the challenge. The pin timing to drive these LED's is somewhat fussy. None of libraries I looked at worked with that fast of a processor. The first problem was that I was using an STM32L board that runs at 80Mhz which is the same speed as the Propeller. The code for the Propeller is pretty straight forward and thought it should be just as easy on the Arduino front. I was building some Arduino code the other day to interface with the WS2812b LED's.