SPI slave mode switching LPC4370

[Gaico]

Hello,

I would like to ask for some help finding out how to switch SPI mode during runtime on the LPC4370. I have considered this post made on a similar issue to what I am experiencing but this does not line up with my possibilities using the LPC. This might be very simple but I appear to be rather stuck in this.

Issue

I am using SSP1, and have three slaves connected to it. Each slave functions on a different SPI mode. During initialization, I successfully communicate with all three:

1. Slave 0 --> SPI mode 1

2. Slave 1 --> SPI mode 0

3. Slave 2 --> SPI mode 3

But after the initialization of slave 2, I need the following functionality inside of an infinite loop:

1. Communicate with Slave 1 (SPI mode 0)

2. Communicate with slave 2 (SPI mode 3)

3. Return to step 1 and repeat

(Slave 0 is not communicated with anymore).

What I am seeing is that after the initiation of Slave 2, if I want to communicate with slave 1, the SPI mode is stuck to SPI mode 3 (which is expected as I am using a pointer to the SSP base, see code). But when using a Logic Analyser, I am seeing behaviour that is more akin to a different SPI mode (I'd expect to see slave 1 communicate in SPI mode 3):

Setting	Slave 2	Slave 1	Result comm. Slave 1 after init. Slave 2
Mode	Mode 3	Mode 0	Mode 2
CPOL	1	0	1
CPHA	1	0	0

Setting	Slave 2	Slave 1	Result comm. Slave 1 after init. Slave 2
Mode	Mode 1	Mode 0	Mode 1
CPOL	0	0	0
CPHA	1	0	1

Wanted situation

 I need to switch the SPI mode rapidly during runtime to interface with two of the slaves:

Setup:

1. Initialize slave 1 in SPI mode 0
2. Initialize slave 2 in SPI mode 3

Infinite loop:

1. Switch SPI mode to 0 (slave 1)
2. Slave 1 (SPI mode 0) --> communicate measurement
3. Switch SPI mode to 3 (slave 2)
4. Slave 2 --> communicate measurement
5. Go back to step 1 inside of the loop

Code used

#define LPC_SSP           	LPC_SSP1

/* Slave 1 initialization */
void SL1_init()
{
    (var 'ports' init)
    Chip_SSP_Disable(LPC_SSP);
    SL1_Init(LPC_SSP, ports, TDC_clock_freq);
}
void SL1_Init(LPC_SSP_T* SPI_BUS, SL_ports config, float Clock_frequency)
{
	Slave1_SPI = SPI_BUS; //global var inside of this file
	SL1_Init_SPI();
	// init ports
	Clock_Frequency = Clock_frequency;
}


void SL1_Init_SPI()
{
	Chip_SSP_Init(Slave1_SPI);
	SSP_ConfigFormat ssp_format;
	ssp_format.frameFormat = SSP_FRAMEFORMAT_SPI;
	ssp_format.bits = SSP_DATA_BITS;
	ssp_format.clockMode = SSP_CLOCK_MODE0;
        Chip_SSP_SetFormat(Slave1_SPI, ssp_format.bits, ssp_format.frameFormat, ssp_format.clockMode);
    Chip_SSP_SetMaster(Slave1_SPI, 1);
    Chip_SSP_SetBitRate(Slave1_SPI, 10000000);
	Chip_SSP_Enable(Slave1_SPI);
}

 For slave 2:

void Init_Slave2(LPC_SSP_T* spi_bus, Slave2_con config)
{
	Slave2_SPI = spi_bus;
	Slave2_Init_SPI();
	//pin init
}

void Slave2_Init_SPI()
{
//	Chip_SSP_Disable(Slave2_SPI);//new

	Chip_SSP_Init(Slave2_SPI);

	SSP_ConfigFormat ssp_format;
	ssp_format.frameFormat = SSP_FRAMEFORMAT_SPI;
	ssp_format.bits = SSP_DATA_BITS;
	ssp_format.clockMode = SSP_CLOCK_MODE3; //can be 1 or 3
        Chip_SSP_SetFormat(Slave2_SPI, ssp_format.bits, ssp_format.frameFormat, ssp_format.clockMode);
    Chip_SSP_SetMaster(Slave2_SPI, 1);
    Chip_SSP_SetBitRate(Slave2_SPI, 1000000);

	Chip_SSP_Enable(Slave2_SPI);
}

Things tried already

Both slaves are changing the pointer directly to LPC_SSP. Which I think is needed? I thought I could 'just' recall the slavex_init_spi() function during runtime, but this resulted in the LPC_SSP C0 register being completely messed up:

Initiation	Measurement loop
Slave 1 as defined before Slave 2	Slave 2 defined	Slave 1 communication (firstly calling the slave1_init_SPI function)
Hex:0xa07 Binary:101000000111	Hex:0x65c7 Binary:110010111000111	Hex:0xfe87 Binary:1111111010000111

Considerations

Do I need to add a forced delay between the re-initiation of the SPI before or after I'm trying to communicate?

I cannot plainly use different SSP ports as the controller is connected to a custom PCB (which has worked before but I do not possess that code).

Thank you for your consideration and take care!

[Gaico · Accepted solution]

The issue was that the 

 Chip_SSP_Disable(LPC_SSP);

 Was not inside of init SPI function. So the SPI was never turned off. Adding this inside of the function made everything work fine.