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CC2530: SPI driving capability

Alan Chen6
Prodigy 70 points
Part Number: CC2530


Hi all expert:

We are using CC2530 to drive one SPI LCD w/o any problem,  and we intend to drive 5 or even more than 5 LCD with same SPI bus, except CS pin, which will be controlled independently.

But, the problem start happened when we connected 2 LCD with same SPI bus (same CS pin, and all Data/CLK pin),  we provided the separate power for VCC, and backlight, so the Power would not be a concern.

The problem we certainly ensure happened on SPI bus.

Before SW jump in to control the each LCD CS pin,  now, HW connect the all same SPI Bus to control the all LCD,  but the problem happened on 2 LCD,   the first LCD caused blurred screen, the 2nd LCD can not show anything.   This is so weired to me, suppose the 2 LCD need to show the same screen no matter the result is good or bad.

1) May I know what kind of possibility to casue this issue?

2) Suppose the CC2530 can drive many LCD with same SPI bus, due to we provided the separated power,   so the SPI driving capability would be not the major concern,  right?

3) How we can drive more LCD on same SPI bus on CC2530?

thanks and Regards

Alan

  • 0
    Guru 735695 points

    Do you add pull-high resistor to all of CS pin, and all Data/CLK pins?

  • 0 in reply to YiKai Chen
    Prodigy 70 points

    The first time was not add any pull-up resistor on SPI bus,   it failed,    then we add the pull-up 4.7Kohm to 3.3V on each signal (CS, Data, CLK) on SPI bus, but got the same bad result.

    The strange thing is, the worse case I need to see the same result on 2 LCD no matter the quality is good or bad.

    But the reality is, I still only can see the 1st LCD display something, but the 2nd LCD still show nothing,   only backlight due to the backlight power is independent.

    Alan

  • 0 in reply to Alan Chen6
    Guru 735695 points

    I would suggest you using protocol analyzer or scope to check SPI signal quality first.

  • 0
    TI__Guru**** 220227 points

    Hi Alan,

    Can you confirm that each LCD operates as expected independently?  And you are sure that only one LCD is enabled through the CS pin each time?  This does not appear to be erroneous error from the CC2530 as compared to a physical connection issue, as YK mentioned you need to confirm that the SPI communication lines are as expected using a logic analyzer or oscilloscope.  It would also be good to monitor the VCC provided to each device and ensure that they stay within the operating recommendations.

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    Prodigy 70 points

    Hi Ryan:

    we wired out to another PCBA, which has all components on, but we only wire the SPI signal, and LCD Power, and backlight power to the board, this means we didnt enable the CC2530 on another board, but the signal are all tie together.  I dont know if this trigger the ''leakage''?

    we had measured the signal by Oscilloscope, same waveform as we measured on 1st LCD, and 2nd LCD,  but only 1st LCD can display the normal screen, 2nd LCD shows nothing.

    I did another test, with bare PCB,  and wire the same path listed above to the new bare PCB, then it works.  2 LCD can works simultanelously. (1 connect to the original PCBA with CC2530 inside,  another connect to the bare PCB, only SPI signal and power go over there)  same, CS pin on both LCD.

    so, the driving capability should be no problem.

    We will try more LCD like this way, and see how many it can drive with.

    Alan