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Using SPI mode to interface msp430 with RFtransciever&SD

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Aug 7, 2009
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msp430 spi mode


I am planning to use SPI mode to interface a eZ430-RF2500 with a Sandisk Secure Digital Card. The eZ430-RF2500 includes a MSP430 microcontroller and a CC2500 RF transceiver. According to the schematic, the RF transceiver interfaces the MSP430 utilizing the SPI mode, using the SOMI, SIMO, SCK, STE(for chip selecting) pins of MSP430.

The problem is can I connect the MSP430 with SD card using the same set of input wires(SOMI, SIMO, SCK, STE)? In this case, I suppose MSP430 is the master, both RF transceiver and SD card are slaves. If it is possible, how to use the STE signal to perform slave selecting. ALL the information I've got is that the chip selecting can be done by using the STE, but no detailed examples to demonstrate it.


msp430 spi circuit


Yes, All you need is to use a different CS (slave select) for each slave device)
I would also add the use of ring buffer and some handling software for each device

All the best


daisy-chaining spi devices (daisy-chain mode)

If the clock rates of ur memory card and the RF interface match u can use daisy chaining technique.
Where the output of one slave passes through the other before reaching the controller.
same is the case in input.
In daisy chaining technique u don't need a slave select.

sd memory card to msp430 interface

Hi Bobcat1,

So far as I know, there is only one cs pinout in the msp430 microcontroller. How to add an another cs for the second slave device if I apply this configuration.


Added after 20 minutes:

Hi Dharanidhar,

It seems the the daisy chain is a good solution too.

But, I've tried to study the schematic of eZ430-RF2500, and I'm not sure whether the msp430 has interfaced with the RF2500 using the single Master-slave SPI Bus implementation. Do u have any idea about it? If the two devices have been connected in this mode, I'm worried about that the daisy chain technology could not be used.

Another question is, does msp430 support daisy chain. Is all microcontrollers that include SPI mode support daisy chain?


interfacing db9 pinout to msp430 microcontroller

Daisy chaining is an external SPI configuration and it has nothing to do with controller
It represents the way the serial interface lines have been routed externally through slaves

I have gone through the schematic.It is connected in single master slave configuration.With this board i think it is not possible to connect in daisy chain mode.The master slave lines have been directly routed to RF2500.

U can plan it other way.Try to trap the MISO, MOSI, SCLK, CS lines from the board.
connect these lines to a latch input and output from latch must go to ur memory chip.
use inverter for CS and connect to memory card.

Try to enable the latch whenever u wanted to route data to memory card.

what is spi mode

Hi dharanidhar,

There is no problem to trap the MISO, MOSI, SCLK, CK lines from the board.

Can I connect these lines directly to memory chip without latches? I don't know why to use latches.

If I use latches, do I need to provide a extral enable signal?


slave spi problems msp430

I don't know how the MSP340's SPI-unit works, but there are two possibilities:
1 The STE chip-sleect output is asserted automatically by hardware when an SPI-transmission starts
2 STE must be asserted by your program just prior to the SPI-transmission being started

If the situation is (1), then you must use a multiplexing circuit to route STE to the selected peripheral, using another CPU output-line as the selector

In case (2), you need to choose another output from the CPU as a new chip-select
and assert that to send to the new peripheral.

In either case, the SIMO,SOMI and SCK lines go to all peripherals

Wade Hassler

Re: Using SPI mode to interface msp430 with RFtransciever&am

Доброго времени суток , товарищи, неподскажите как при использовании отладочного комлекта eZ430-RF2500 (связка MSP430 и СС2500) вытащить значения регистров СС2500? и очень было бы хорошо иметь возможность посмотреть что в нём твориться, то есть получить вывод данных на консоль состояния СС2500.

Re: Using SPI mode to interface msp430 with RFtransciever&am

It is better to configure the STE line as GPIO and then use as CS. Because some of the SPI devices need CS to be active between consecutive transfers. If you use STE it will go into inactive state between continous transfers.

This ways you can add as many SPI devices as you want by just using any spare GPIO as CS. In the spi data transfer routine you can assert and deassert CS for any particular device you want to talk to.

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