Tag: RS232

Arduino – MCP42010 controlling several digital potentiometers in cascade

Post author By Henry Koch
Post date 20. October 2020
No Comments on Arduino – MCP42010 controlling several digital potentiometers in cascade

Arduino – MCP42010 – Example of controlling several digital potentiometers

After the example Arduino – control and test digital potentiometer MCP42010 on breadboard and the graphic variant Node Red – Arduino – control digital potentiometer MCP42010 I tested the control of 2 digital potentiometers MCP42010 cascaded.

circuit

Arduino Nano - MCP42010 kaskadiert_auf_Steckplatine — MCP42010 on the Breadboard

Arduino Nano - MCP42010 Steckplatine Fritzing — Fritzing Design MCP42010

Arduino Nano - MCP42010 kaskadiert Eagle Schaltplan — Eagle Design MCP42010

Arduino Nano - MCP42010 kaskatiert_Datenblatt — Scheme MCP42010

Control of the two MCP42010

The control of the primary MCP42010 is described in detail in Arduino – Control and Test Digital Potentiometer MCP42010 on breadboard.
Write in potentiometer 1 -> B00010001 and in potentiometer 2 -> B00010010
The value that the selected potentiometer should set is transmitted as the second byte.

To reach the second MCP42010, 4 bytes have to be sent instead of 2 bytes for a single one.
With three MCP42010 6 bytes are required, with four 8 bytes and so on.
In order to control a potentiometer of the second MCP42010 directly without changing the contents of the first chip, two more bytes with the value 0 are sent.
See also the picture on the left from the data sheet.

Write in potentiometer 3 -> B00010001 value B00000000 B00000000
Write in potentiometer 4 -> B00010010 value B00000000 B00000000

The whole thing has to be read from right to left.
4 bytes are written, or better shifted into it.
The first two bytes (from the left) are shifted from the following two bytes into the second MCP42010.
Two bytes with ‘zero’ arrive in the first MCP42010, i.e. no changes to the values in the 1st chip.

Here is a minimal example of how the value 127 is loaded into potentiometer 1 (Pot0) of the second MCP42010.

Tags Arduino, COM port, electronic, MCP42010, Programmieren, RS232

Node Red

Arduino – Node Red – MCP42010 control the digital potentiometer

Post author By Henry Koch
Post date 8. February 2017
2 Comments on Arduino – Node Red – MCP42010 control the digital potentiometer

Arduino – Node Red – MCP42010 – Sample control of the digital potentiometer

In the article Arduino – control and test digital potentiometer MCP42010 on a breadboard I showed how the MCP42010 can be controlled via the serial monitor of the Arduino IDE.
Now I want to do this more comfortably.
The operation has to take place from the browser, should look visually very appealing and it must also be possible with the smartphone.

Why with Node Red?

Node Red is included in the standard installation of the Raspberry Pi, free and intuitive to use.
By the possibility of clicking together the flow by drag and drop together, one comes very quickly to a good result.
For prototypes and also IOT applications this is a really great thing.
Where light is, is also shadow: Node Red consumes quite a lot of resources.
Nevertheless, the Raspberry Pi 2 does well and the performance with the Pi 3 should still much better.

Required functions of the flow

The flow is supposed to take over the entries, which I have done by hand in the Arduino – control and test digital potentiometer MCP42010 on a breadboard.
The flow should represent the return values in a Gauge Chart.

data input:
1:Value between 0-255 -> sets potentiometer1 to the value and returns the voltage to A0
2:Value between 0-255 -> sets potentiometer2 to the value and returns the voltage to A1

The Flow

copy the following flow and insert it under menu (top right) -> Import – Clipboard

[{"id":"ebf0e947.110038","type":"ui_slider","z":"8ec3bd3.cce4dc","tab":"147200e2.b8e19f","name":"Slider","topic":"","group":"Pot1","order":1,"min":0,"max":"255","x":225.5,"y":125,"wires":[["25bd2695.9acaf2"]]},{"id":"b755b484.2bd75","type":"ui_text","z":"8ec3bd3.cce4dc","tab":"147200e2.b8e19f","name":"Wert","group":"Pot1","order":1,"format":"{{msg.payload}}","x":636.5,"y":102,"wires":[]},{"id":"ed9f01b2.dfae38","type":"ui_gauge","z":"8ec3bd3.cce4dc","tab":"147200e2.b8e19f","name":"Spannung in V an A0","group":"Pot1","order":1,"format":"{{value}}","min":0,"max":"5","x":681.5,"y":322,"wires":[]},{"id":"25bd2695.9acaf2","type":"function","z":"8ec3bd3.cce4dc","name":"Value to Command","func":"var msg1 = { payload:\"1:\" + msg.payload +\"\\n\"};\nreturn [msg, msg1];","outputs":"2","noerr":0,"x":440.5,"y":125,"wires":[["b755b484.2bd75"],["134514.6c0042ed"]]},{"id":"134514.6c0042ed","type":"serial out","z":"8ec3bd3.cce4dc","name":"/dev/ttyUSB0","serial":"d535ccdc.123838","x":658.5,"y":148,"wires":[]},{"id":"13db30d1.da3c67","type":"serial in","z":"8ec3bd3.cce4dc","name":"/dev/ttyUSB0","serial":"43aa993f.185738","x":186.5,"y":345,"wires":[["f39416bc.0495"]]},{"id":"f39416bc.0495","type":"function","z":"8ec3bd3.cce4dc","name":"Response to value","func":"//find A0 or A1\nvar value;\nif (msg.payload.indexOf(\"A0\") != -1) {\n    value = msg.payload.split(\"A0: \");\n    value = value[1].replace(\" Volt\", \"\");\n    msg.payload = value;\n    return [msg, null];\n} else {\n    value = msg.payload.split(\"A1: \");\n    value = value[1].replace(\" Volt\", \"\");\n    msg.payload = value;\n    return [null , msg];\n}","outputs":"2","noerr":0,"x":431.5,"y":345,"wires":[["ed9f01b2.dfae38"],["ddbfff6.2bdb3"]]},{"id":"8a48ef7d.33ba9","type":"ui_slider","z":"8ec3bd3.cce4dc","tab":"147200e2.b8e19f","name":"Slider","topic":"","group":"Pot2","order":1,"min":0,"max":"255","x":224,"y":227,"wires":[["127d632d.c0419d"]]},{"id":"5a58be54.e6b8d8","type":"ui_text","z":"8ec3bd3.cce4dc","tab":"147200e2.b8e19f","name":"Wert","group":"Pot2","order":1,"format":"{{msg.payload}}","x":635,"y":204,"wires":[]},{"id":"127d632d.c0419d","type":"function","z":"8ec3bd3.cce4dc","name":"Value to Command","func":"var msg1 = { payload:\"2:\" + msg.payload +\"\\n\"};\nreturn [msg, msg1];","outputs":"2","noerr":0,"x":439,"y":227,"wires":[["5a58be54.e6b8d8"],["ee1b0407.9fbca"]]},{"id":"ee1b0407.9fbca","type":"serial out","z":"8ec3bd3.cce4dc","name":"/dev/ttyUSB0","serial":"43aa993f.185738","x":657,"y":250,"wires":[]},{"id":"ddbfff6.2bdb3","type":"ui_gauge","z":"8ec3bd3.cce4dc","tab":"147200e2.b8e19f","name":"Spannung in V an A1","group":"Pot2","order":1,"format":"{{value}}","min":0,"max":"5","x":681,"y":370,"wires":[]},{"id":"147200e2.b8e19f","type":"ui_tab","z":"","name":"Test MCP42010","icon":"dashboard","order":"1"},{"id":"d535ccdc.123838","type":"serial-port","z":"","serialport":"/dev/ttyUSB0","serialbaud":"9600","databits":"8","parity":"none","stopbits":"1","newline":"\\n","bin":"false","out":"char","addchar":false},{"id":"43aa993f.185738","type":"serial-port","z":"","serialport":"/dev/ttyUSB0","serialbaud":"9600","databits":"8","parity":"none","stopbits":"1","newline":"\\n","bin":"false","out":"char","addchar":false}]

Video Controlling MCP42010 with Node Red

Tags Arduino, tinkering, COM port, electronic, MCP42010, Node Red, Programmieren, RS232, Serielle Schnittstelle, Video

Raspberry Pi

Raspberry Pi – homemade level converter for serial communication rs232 3.3 volts to 5 volts TTL for AVR microcontroller

Post author By Henry Koch
Post date 2. November 2014
No Comments on Raspberry Pi – homemade level converter for serial communication rs232 3.3 volts to 5 volts TTL for AVR microcontroller

I found that the Raspberry Pi serial interface rs232, described in a older post by myself, was too bulky.

Pi and AVR should be connected through a less amount of wires.

So I’ve searched the best hints to solder a cheap and uncomplicated level converter, that can directly be connected between the GPIO of the Pi and the rx/tx pins of the microcontroller.

On the German website http://www.elektronik-kompendium.de/sites/praxis/bausatz_pegelwandler-mit-transistoren.htm I found a useful circuit with transistors and resistors that I had in my toolbox. (something similar but also matching parts)

The following images are showing my circuit diagram and the test setup.

The first test worked flawlessly both in the direction to the Pi and in the direction to AVR microcontroller.

The third picture shows the circuit diagram used and the fourth image the development on breadboard. Now I can connect my test board and the Pi over normal jumper cable to have hanging around without various additional boards.

Tags ATMega8, ATMEL, AVR, Raspberry Pi, RS232, Serielle Schnittstelle

Raspberry Pi

Raspberry Pi – using the serial interface (RS232)

Post author By Henry Koch
Post date 20. September 2013
6 Comments on Raspberry Pi – using the serial interface (RS232)

The Raspberry Pi is equipped with many interfaces.
And the possibilities can rise more than exponentially by using of the USB port.
But to communicate with AVR microcontrollers is the best suited way by using a serial interface.
Of course, the Raspberry Pi A has a serial interface, but unfortunately merely as pins on the GPIO connector.

The required pins, could be connected theoretically directly to the microcontroller eg. ATMega8.
But that would require that the microcontroller operates at 3.3 volts.
My Pollin evaluation board works with 5 volts, but is made with a complete RS232 interface for communication with PC or other equipment.
The easiest way would it be, when the Pi would have an RS232 interface like a PC with the same connectors and signal levels.
By Googling I’ve found the website Serial Port Add On.
The described Serial Port to TTL Digital Converter Module there, I’ve bought at Ebay.

GPIO Header Pins

2	4	6	8	10	12	14	16	18	20	22	24	26
1	3	5	7	9	11	13	15	17	19	21	23	25
1= 3.3V, 9= GND, 8= TX, 10= RX

The jumper cables to connect to the Raspberry Pi were included in the delivery.
I’ve connected the module with the Pi, as shown in the picture below.

To get the serial interface up and running, are some changes in/etc/inittab and /boot/cmdline.txt necessary.

/etc/inittab

comment line: ‘T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100’

#Spawn a getty on Raspberry Pi serial line
#T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

/boot/cmdline.txt

delete of: dwc_otg.lpm_enable=0 ~~console=ttyAMA0,115200 kgdboc=ttyAMA0,115200~~ console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

pictures of my PI inclusive ‘serial device’

RaspberryPI_mit_serieller_Schnittstelle_VS

RaspberryPI_GPIO_serielle_Schnittstelle1_VS

RaspberryPI_GPIO_serielle_Schnittstelle2_VS

RaspberryPI_GPIO_serielle_Schnittstelle3_VS

RaspberryPI_GPIO_serielle_Schnittstelle4_VS

Video, for Demonstration

The video is already on my ‘Hello World Example’ in the ATMega8 area of my website in use.

For that I’ve written a little perl script. Surely it is possible to use programs like minicom, but I dont wanted to spend the time to familiarize myself with a new tool.
The script was written faster and from my perspective it’s much more flexible for further use and for experiments.