topic Re: LPC18S37 and SSP1 clock signal issue in LPC Microcontrollers

LPC18S37 and SSP1 clock signal issue

sener — Sun, 28 Nov 2021 23:15:16 GMT

Hi,

I have a custom board with LPC18S37 and an LCD connected via SPI (only MOSI, SCK, CS and DC).
Since I couldn't have success on interfacing LCD, I've started to troubleshoot hardware and software respectively. Hardware side seems to be alright and I've started to look in the code.

I am using files from NXP for drivers and examples (you may see them attached).

Here is the simplified code from my work;

lpc1850_db1.h

#include "/Drivers/Include/lpc18xx_scu.h" /* HW Name PinName TFBGA100 Name Type Func Port Pin LCD_L_CS P1_0 H1 GPIO0[4] I/O 1 0 4 SSP1_SCK PF_4 H4 SSP1_SCK I/O 1 SSP1_MOSI P1_4 J2 SSP1_MOSI I/O 6 0 11 */ #define LCD_L_CS_SCU_CONFIG 0x1, 0, MD_PLN, FUNC0 // LCD_L_CS #define LCD_SCK_SCU_CONFIG 0xF, 4, MD_PLN_FAST, FUNC0 // SSP1_SCK #define LCD_MOSI_SCU_CONFIG 0x1, 4, MD_PUP | MD_EZI | MD_ZI, FUNC5 // SSP1_MOSI #define LCD_L_CS_SCU_PORT 0x1 #define LCD_L_CS_SCU_PIN 0 #define LCD_L_CS_GPIO_PORT 0 #define LCD_L_CS_GPIO_PIN 4 #define LCD_L_CS_GPIO_MASK (1 << LCD_L_CS_GPIO_PIN)

main.c

#include "RTOS.h" #include "LPC18xx.h" // Device specific header file, contains CMSIS #include "LCDST7735.h" #include "LCDMain.h" #include "Common.h" #include "/Drivers/Include/LPC18xx_ssp.h" #include "../OS/Setup/Boards/lpc1850_db1.h" SSP_CFG_Type SSP_ConfigStruct; scu_pinmux(LCD_SCK_SCU_CONFIG); scu_pinmux(LCD_MOSI_SCU_CONFIG); // initialize SSP configuration structure to default SSP_ConfigStructInit(&SSP_ConfigStruct); // Initialize SSP peripheral with parameter given in structure above SSP_Init(LPC_SSP1, &SSP_ConfigStruct); // Enable SSP peripheral SSP_Cmd(LPC_SSP1, ENABLE); OS_Delay(200);

The rest of the code, LCD related command and data.

Here is the shot from the scope which I find it very interesting.

Looks like SCK and LCS (CS actually) are switched their places. I thought that I swapped the probes by mistake. No, it wasn't actually, they were correct. I've also traced back the connections up until the LPC18S37 pins. They are also correct.

From this point, before I continue my troubleshooting on the LCD interfacing, I like to understand what happens here. For example, am I making a mistake in pin muxing and it is resulting in this issue? Any pointer greatly appreciated.

Re: LPC18S37 and SSP1 clock signal issue

Alice_Yang — Tue, 30 Nov 2021 03:13:58 GMT

Helllo sener,

If pin mux configuration like your below comment, it is wrong.

/*
HW Name  PinName    TFBGA100	Name	       Type    Func   Port     Pin
LCD_L_CS      P1_0	H1	GPIO0[4]	I/O	1	0	4
SSP1_SCK      PF_4	H4	SSP1_SCK	I/O	1	
SSP1_MOSI     P1_4	J2	SSP1_MOSI	I/O	6	0	11
*/

Alll the Func number need subtract 1.

Alice

Re: LPC18S37 and SSP1 clock signal issue

sener — Tue, 30 Nov 2021 09:49:34 GMT

Thank you for your response Alice.

But, I can't see if it is wrong with the function number.

/* Pin function */
#define FUNC0 0x0 /** Function 0 */
#define FUNC1 0x1 /** Function 1 */
#define FUNC2 0x2 /** Function 2 */
#define FUNC3 0x3 /** Function 3 */
#define FUNC4 0x4
#define FUNC5 0x5
#define FUNC6 0x6
#define FUNC7 0x7

Re: LPC18S37 and SSP1 clock signal issue

Alice_Yang — Wed, 01 Dec 2021 08:22:14 GMT

Hello,

Compare with the configuration with SSP demo, and confirm your connection .

Re: LPC18S37 and SSP1 clock signal issue

sener — Wed, 01 Dec 2021 23:01:46 GMT

For whom has a similar issue, I mark my solution here.

I solved the issue with SPI and LCD at the same time. It was just a missing line. Since my LCD doesn't need the MISO line, I have just ignored it since the beginning. Reading after reading, although it wasn't clearly written anywhere, I finally came to a conclusion that MISO line has to be setup anyway. I did so and It worked!

You must pinmux MISO line!

#define LCD_MISO_SCU_CONFIG 0x1, 3, MD_PLN | MD_EZI | MD_ZI, FUNC5 // SSP1_MISO scu_pinmux(LCD_MISO_SCU_CONFIG);

Note that: Besides, although things are working OK now, I have still more or less same scope output. So, don't ask (I don't ask anymore) why the scope output is like that which was my original question.

Best regards,
Sener