INA219 Current Sensor DIY Breakout board

Another small board, this time for a INA219. The INA219 is a high-side current shunt and power monitor with an I2C interface.


For testing I used Rei VILO library with a MSP430G2553 and Energia, and I measured the power consumption for this simple circuit:

2 001-001

Nothing fancy, just a led and a resitor. The INA219 should measure around 9.6 mA and got this:


The current measurement is slightly off. I need to play a litlle more with the calibration routines.


SHT21S DIY Breakout board

I made a little board for a SHT21 humidity and temperature sensor from Sensirion.  There are several versions with I2C interface, PWM output and SMD/analog interface.

I’ve got the one with Sigma Delta Modulation (SMD) output,  is a bit-stream of pulses; the more high pulses the higher the value in the full measurement range. A low-pass filter convert the pulse stream to an analog voltage signal.

It has a control pin (SCL) to select between humidity or temperature output. SCL high yields humidity output, SCL low yields temperature output.


I made a simple sketch in Energia to test it out using an MSP430G2553. P1.6 selects between humidity or temperature and P1.0 is used as the ADC input.


…and logged both temperature an humidity.

Sin título

That’s it, a simple and nice sensor…

DIY ez-FET lite…ghetto style

I have a few MSP430G2955 around but non of my Launchpads are capable of programming this MCU. Texas Instruments released a while back all the informtation needed to build the new ez-FET lite. The eZ-FET lite is a low cost USB-based on-board emulation solution for MSP430 microcontrollers. This debuger supports all MSP430 devices compatible with SBW programming and I could use it to program the MSP430G2955.

The hardware is based on an MSP430F5528 and I used a QFN version with an adapter board:



it ain’t pretty…

In order to program the MSP430F5528, I tried first using the FET-Pro430 from Elpotronic. I was able to flash the BSL firmware:


despite an error dialog about code size:


…then, I programmed the ez-FET firmware:


After reseting the programmer all the drivers were installed:


But every time I tried to program a device with CCS I would get this error message:


ok, fail…let’s start over.

According to this post the error might be caused by the the custom BSL portion of the ezFET firmware being not properly flashed.  I did read this other post in 43oh about flashing the firmware with MSP430Flasher, I just wanted to see if the Elpotronic software would work.

I tried  to re-program the MSP430F5528 using MSP430Flasher but I get this “BSL memory segments are protected” error.


According to this post I have to add options to unlock  BSL memory as well as the INFO A memory. I added for that -b and -u:


Success!! At least the BSL.  Then I attemped a firmware update with MSP430Flasher:


More success!!! I should have tried this in first place…

Anyway, I tested the programmer with the old and beloved “blink” and It’s working. I still need to test the UART interface but this should work as well.


Constant Current Electronic Load

I’m building a power supply and an electronic load might be useful for testing it, so I made one.

Electronic Load/ Carga electrónica

The design is based on some of the various diy electronics loads out there (like the one from Dave Jones). The mosfet is a P45N03LT , most likely I took it from some of the PC power supply I’ve “recycled”.  I’m using two 25k potentiometers, one for coarse adjustment and the other for fine adjustment (10 turn pots are kind of expensive…). The control voltage varies between 0 and 5 volts and is divided by two with a couple of 10k resistors. The op-amp is an OPA2336, It has rail to rail output so the load can sink roughly up to 2,5. The op amp is powered with a 7805.

Electronic Load/ Carga electrónica

The sense resistor is made with a series of 10 0.1 ohm, 1[w], 1% resistors. I made two “resistors” soldering 5 of them and then I put these two back to back and used kapton tape to keep them electrically isolated.

Electronic Load/ Carga electrónica

Finally a heat sink (scavenged form a PC supply as well) for the mosfet and some female banana plugs. The heat sink is too small and it gets really hot, I will have to find a bigger one or put some kind of cooler fan.

Electronic Load/ Carga electrónica

A few components for a very handy piece of equipment.

Electronic Load/ Carga electrónica