Digital Potentiometer MCP41100 SPI

Device Code
1

Can someone tell me how can I set the resistance of this pot?

I tried the code provided on the website : https://electricimp.com/docs/api/hardware/spi/configure/ but it doesn’t seems to be working for me. The resistance from A to the wiper is still at the midpoint. Also I would like to know how to connect it properly. I am using SPI 257 and Pin9 as the Chip select (CS).

Thank you very much in advance.

2

Looks like you forgot to link to the component?

3

Sorry about that ww1.microchip.com/downloads/en/DeviceDoc/11195c.pdf that is the link for the datasheet of potentiometer used. I tried to connect the CS to the Ground (Always Enable). But it doesn’t seem to work.

4

Usually SPI slaves need the nCS line to go low at the beginning of each command: the high-to-low transition marks the start of the command.

Peter

5
Usually SPI slaves need the nCS line to go low at the beginning of each command: the high-to-low transition marks the start of the command.

Peter

I did that but it doesn’t seem to be working. The resistance between Terminal A and the wiper is not changing.

`

CS ← hardware.pin9
CS.configure(DIGITAL_OUT_OD_PULLUP);
SPI ← hardware.spi257
SPI.configure(SIMPLEX_TX | MSB_FIRST | CLOCK_IDLE_LOW, 400);

function send()
{
CS.write(0);
local resistance = blob(1);
resistance.writen(0x01, ‘b’);
SPI.write(resistance);
CS.write(1);
}

send();

`

This is my code. Not sure if there is anything wrong with it.

6

I also checked the wave coming out of pin9(CS), pin5(CLK) and pin7(MOSI). But I got sine wave out of it. Should I not be getting square waves ?

7

The datasheet (tables 5-1 and 5-2) suggests that you need to write a command-byte followed by a data-byte.

Peter

8

So can you give me a brief idea what would the code looks like? Thank you very much.

9

eg:

SPI.write(format("\\x11%c", 100));

…writes (the first “1” in the \x11) to pot 0 (the second “1” in \x11 - pot 1 would be \x12), the value 100.

No need to create a blob for this.

10

Got it working. Thank you very much guys. Appreciated.