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USB on STM32F10x µCs
Every µC from the STM32F10x family has hardware built-in to support USB. The earlier (i.e. smaller) STM32F103’s have a more limited implementation that more recent models. There are some really strange...
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And so Forth...
This week’s episode will be a short one, as I try to push though some issues and prepare for greater things to come.First, a little progress report on getting USB going in Mecrisp Forth on the...
View ArticleForth in 7 easy steps
Forth is a simple language, with simple rules and a simple execution model. It’s also self-hosted and interactive - you can type this at the prompt:1 2 + .<cr> What you’ll get as response is this...
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Preparing for serial re-flashing
The STM32F103 µC chips all have a ROM-based boot loader on board. Most chips variants can only be re-flashed via USART1, using the PA9 and PA10 pins, so we will need to connect to that serial port...
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From Zero To Wireless
This week, I’m going to set up a wireless node from scratch, using an STM32F103 board, RFM69 radio module, serial USB interface board, and very simple software:The result is a node with all the...
View ArticleA new serial tool: vive la Folie!
Working with embdded µC boards involves quite a few steps: apart from the hardware itself, you need to connect to it and figure out how to upload code, of course. But you also think about the...
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Adding the RFM69 module
The last step to create a wireless node is to hook up the RFM radio. Here is what we’re after:There are 4 signals and 2 power pins to connect (more can be added later, for pin...
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The limitations of the ADC
The Analog-to-Digital-Converter (ADC) we all know from Arduinos and other µCs is a marvel of integration and electronics engineering. Able to measure at rates of over a million samples per second...
View ArticleAnalog Explorations
There are many projects going on in parallel here at JeeLabs at the moment. One reason is that I’m simply always chasing new butterflies… ehm, I mean areas of technology. Another one is that sometimes...
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Measuring negative voltage
The task to be tackled here is measuring voltage ranging from +N to -N Volt with an ADC input which needs to be kept in the range 0 to 3.3V.There are numerous resources all over the web which solve...
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Op-amps and virtual ground
The voltage-divider-tied-to-3.3V trick allows shifting the level of an input voltage to another range. But there are a few issues with it.The first one is that we still cannot measure anything above...
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Fixing the offset problem
There is still a fairly serious flaw in our little voltmeter setup: its Vin input is not at ground level. It’s connected via Z1 and Z2 to that 2.4V or so virtual ground we just created, and when Vin is...
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Let's measure ± 20V @ 11MΩ
So much for theory and design. Here’s a built-up version of the voltmeter:It was built as add-on for the RF Node Watcher, here’s the side view of this sandwich:Everything was built with through-hole...
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Slowed-down by the slew rate
Let’s re-visit the voltage meter for a moment - the actual circuit used in the next test differs in a few resistor values, but it’s still essentially the same as the triple op-amp setup described...
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Real op-amps
Operational amplifiers are the work horses of analog. As a symbol (from Op amps 101):There are lots of low-cost op-amps available these days. Easy-to-use 8- or 14-pin chips, with 1, 2, or 4 op-amps in...
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Op-amp parameters explained
It can’t be shown often enough - the most elegant building block in electronics:In an ideal op-amp …the V+ and V- inputs have infinite resistancethere is zero current into and out of both V+ and V-if...
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Better speed and sensitivity
First off, let’s find out how that last single op-amp circuit works in practice. The chip used is an LMC6484 quad CMOS op-amp with extremely high input impedance. Since it’s also rail-to-rail on both...
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Water damage
We recently had a small water leak in the kitchen - leading to a 3-hour server outage for JeeLabs. Very early in the morning, so very few people will have noticed it - other than an ever-vigilant...
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Water and electricity don't mix
The hot water tap in the kitchen at JeeLabs is provided by what’s called a “close-in boiler” in the Netherlands: a small 7L electrical boiler, sitting under the kitchen sink and hooked up with two...
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And then the JeeNode stopped
Unfortunately, the USB power supply is not all that got damaged by the water leak:There’s a blueish sludge on the RJ12 jack. Presumably some copper salt caused by humidity and corrosion. This is a...
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