Where I discuss several versions of Forth and the attributes of each.
Forth Versions
There are many versions of Forth. This is due to a variety of reasons:
Forth as a language is over 60 years old, hence there has been a significant amount of time for it to evolve.
Forth tends to be processor-focused. Some people might argue this point, however, due to Forth’s ability to work well at a low-level, implementations tend to be aimed at a particular processor than other high-level languages.
Forth is a relatively easy language to write and it is extensible, which means its not unusual for someone to “roll their own version”.
I discuss designating ESPForth as ArduinoForth, which is Forth words calling the Arduino framework.ESPForth is one of the easiest and least expensive ways to learn Forth, however it is based on the Arduino framework. This entry continues to explore how to use ESPForth calling Arduino routines on the Adafruit ESP32 HUZZAH32.
Change of plans (again)
This entry is pretty much deprecated for two reasons:
There is a bug (or I don’t understand it) in CH Ting’s version of ESPForth in the word “constant”. Through several attempts over multiple months, I haven’t been able to have it consistently store a value. I looked at the C++ code and wasn’t able to determine the issue. Ultimately, this prevents one from writing a readable Hardware Abstraction Level (HAL), as much of an HAL are constant definitions.
While attempting to solve #1, I ran across a new version of ESPForth, ESPForth 7.0.
Change of plans
For several days, I attempted to use the HUZZAH32 in its native mode, meaning I look at the registers such as GPIO_OUT_W1TS_REG and set specific pins to achieve what I need. I ran into significant issues, with some pins working well, while others had inconsistent results. It was this inconsistency that caused me to rethink how I approached this specific version of Forth, ESPForth.
Where I explore filters in electronics and use the Espotek Labrador to demonstrate how to understand filters and create amplitude response curves. This discussion will be absurdly simplistic in comparison to the topic. My goal is to show sufficient theoretical examples of filters, so we can then test them using the Labrador.
Video: How to Use the Espotek Labrador to Analyze a High Pass Filter Amplitude Response Curve
Our goal with the Labrador is to test the following filter analysis. Doing so will help make electronics more intuitive and familiar and help you understand as to how to use the Labrador. It will also help you understand how to plot data and in this case, using a log scale.
When I started using Python, I didn’t use the Python REPL much. I took a more conventional approach to running Python as a scripting utility using executable files. When I started using Julia, I found the REPL much more valuable than Python’s. It might be the same, however, I’ve found myself using Julia via the REPL far more than as a scripting language. A couple of pointers:
ESPForth is one of the easiest and least expensive ways to learn Forth.
esp32Forth Serial Monitor is a version of Forth written by CH Ting. Ting is remarkable in the volume of documentation he provides, as well as the number of versions of Forth he has created. In this article I want to highlight a version that I believe is interesting for two specific reasons:
It runs on a Forth Virtual Machine (FVM) using the Arduino software framework
It runs on ESP32 Arduino boards such as the NodeMCU ESP32, Adafruit ESP32 HUZZAH32 and the ESP32-DEVKIT. Most of these boards are $5-$15 with an amazing amount of processing power. When looking for a board for ESPForth, you want to ensure it is compatible with the Arduino IDE.
FVM on the Arduino software
Using the Arduino software provides a simple, yet powerful IDE for the user to implement Forth. It doesn’t require additional hardware so the user can immediately begin to use Forth. This also allows one to create Forth words calling Arduino framework software such as digitalRead, digitalWrite, and pinMode.
Using potentiometers for programmable bias and gain on the amplifier.
A Typical Problem
If you followed the last couple of experiments, AC Signal Analysis and DC Sweep, you know you have a functional amplifier that will take either a DC level or AC signal and amplify it -2.5x. How do you know this? You were able to test the amplifier using the Labrador’s built-in Signal Generator.
This is nice, if that is the only signal you want to amplify. However, that isn’t the point of electronics! We want to explore and use our amplifier to amplify unknown signals! We want to put it to use!
Using the Labrador to examine the amplifier’s AC signal response.
Compared to the DC Sweep experiment, AC signal response is far easier to do.
Before we dive into how to perform the analysis, let’s discuss why we made the decision to add a bias resistor. Let’s start with the same amplifier design, however, we’ll use two supplies:
From the time domain graph, you can see a few things:
Using the Labrador and a DMM, perform a DC sweep of an inverting amplifier. From our previous lab post we saw the simulation values for a DC Sweep. In this lab, we’ll use the Labrador along with a DMM to determine if our measured values match those of the simulation.
Build the Circuit on a Breadboard
Using this circuit, implement on a breadboard so it is similar to the image below.
Parts List:
LM358 Operational Amplifier
Frequency Generator (Espotek Labrador or ADALM1000)
9V power supply
2k ohm resistor (or 10k potentiometer)
5k ohm resistor (or 10k potentiometer)
Notes:
Vo is pin 1 on the chip
Vn is pin 2 on the chip
Vp is pin 3 on the chip
Make sure you attach 9V to pin 8 and Ground to pin 4
Using a Potentiometer as a variable voltage source
Notice the potentiometer on the right on the breadboard. There are three terminals:
