Use of two (or more) SPI ports at once

[ToPi 0]

Hi!

 

First of all, thank you for creating this great project. I am thinking about switching to Arduino/Energia from mbed (and Arduino before).

However, I have a question: My project requires communicating with at least two SPI devices at once (read data from a sensor, put data into a circular buffer, write it then on SD-Card). It is not possible to use a single SPI with different CS-lines. 

 

How would the code look for this? In this forum, I found "SPI.setModule(0)", but in Arduino, I have only a single SPI object...

 

Thank you for any hint in advance,

Tobias

[roadrunner84 466]

Except for the MSP430G2955 or MSP430F... the usual launchpad chips do not support more than one SPI port at once. This limitation can be overcome by using software SPI, I guess there are people who made a library for this, since SPI isn't that complicated at all.

If you fail to find one, I can write one up for you if required, though I'd like to know how timing etc. should be handled in this case.

[gwdeveloper 275]

The g2553 has 2 spi ports. I don't think it's possible to use any them absolutely simultaneously though. There will always be a minimal but countable cycle delay. Just figure out if it is faster to R/W to different ports or to just use different CS pins.

[roadrunner84 466]

TS stated that using CS to alternate isn't possible (for some obscure reason), but he didn't state that absolute parallelism is required. I think you can write to one SPI port without it affecting anything else, but the code to communicate with the SPI peripheral itself takes some cycles.

[ToPi 0]

Hi, thank you for the suggestions and the quick response!

 

I plan to use the Stellaris LaunchPad Evaluation board (EK-LM4F120XL) which carries the Stellaris LM4F120H5QR.

According to the pinout map of the board and to the Datasheet of the MCU it has four SPI ports.

Unfortunately, my application really requires two independent SPI ports. I managed to et this up with the mbed (NXP Arm Cortex M3 processor, higher price, two SPI) without issues. Therefore I am shure that it will work with the TI chip as well.

 

But my big question now is: How would it work? Can I do it with the Arduino/Energia SPI-Class, or will I need to copy&rename the SPI-class, e.g. SPI2, and assign pins of another hardware SPI port?

Again, my question relates to use of Energia IDE.

 

Thank you everybody for suggestions,

 

Tobias

 

Edit: Working synchroneus is not necessary

[roadrunner84 466]

Erm... Energia does only work with the MSP430, which is a totally different processor than the Stellaris. They just happen to both be made by Texas Instruments.

Never mind me, Energia does support the stellarpad.

[Rei Vilo 695]

You can use software SPI, which comes standard in Energia implementation..

 

Learn more about shiftIn() and shiftOut().

 

Speeds are lower than with hardware SPI but match perfectly SD card.