c - 试图了解 Microchip PIC16LF15344 I2C 外围引脚选择

Question

我一直在查看有关外设引脚选择的 Microchip PIC16LF15344 数据表，要么我读错了它，要么它在文档中似乎有错误和不一致。我想知道是否有其他人使用过此设备并可以确认我的解释。

我正在尝试为 PIC16LF15344 编写代码以使用 I2C 接口(interface)。我已经设法为一个工作正常的 PIC16LF1822 编写了 I2C 代码，但到目前为止我无法让它在 PIC16LF15344 上工作，数据表中有一些令人困惑的文档，我想清理一下。

这里是对 datasheet 的引用.

PIC16LF15344 的pinout 说明表明I2C SDA 功能可以分配给RC1 或RB6。同样，I2C SCL 可以分配给RC0 或RB4。但是在Section 15.3 Bidirectional Pins中有注释如下。

The I2C SCLx and SDAx functions can be remapped through PPS. However, only the RB1, RB2, RC3, and RC4 pints have the I2C and SMBus specific input buffers implemented (I2C mode disables INLVL and sets thresholds that are specific for I2C). If the SCLx or SDAx functions are mapped to some other pin (other than RB1, RB2, RC3, or RC4), the general purpose TTL or ST input buffers (as configured based on INLVL register setting) will be used instead. In most applications, it is therefore recommended only to map the SCLx and SDAx pin functions to the RB1, RB2, RC3 or RC4 pins.

问题不仅是注释似乎与管脚分配表中的描述冲突，它还引用了管脚 RB1 和 RB2，但它们并没有出现管脚分配表中的任何位置，即对于此 PIC，它们似乎不存在。我看到了对 RB1 和 RB2 的类似脚注引用，但它们没有记录在文档正文或表格中的任何位置。

当然，这一定是文档错误，但我在 PIC16LF15324/44 数据表上找不到当前勘误表来更正此问题。我没看错吗？

我已尝试使用 PPS 配置 SCL 和 SDA 以固定 RC0 和 RC1，因为这就是它们在我的 PCB 上的接线方式，但我无法让 I2C 使用与我用于 PIC16LF1822。 EUSART TX2 和 RX2 的 PPS 默认值是 RC0 和 RC1。这是否意味着在使用 SSP1CLKPPS 和 之前，我需要使用 TX2CKPPS 和 RX2DTPPS 将 EUSART 赋值移动到别处>SSP1DATPPS 将SCL 和SDA 分配给RC0 和RC1？

我将调查我的 PCB 的其他潜在问题，但我想在提交另一个 PCB 用于晶圆厂之前解决这个问题。无论如何我需要做一些改变，所以我可能只是将 SCL 和 SDA 连接到它们在下一个版本中的 PPS 默认值，然后再试一次。

初始化代码如下:

OSCFRQbits.HFFRQ = 0b011; // Set internal HF oscillator frequency to 8 MHz
WPUA   = 0b00111111;    // Enable all weak pull-up resistors on port A
WPUB   = 0b11110000;    // Enable all weak pull-up resistors on port B
WPUC   = 0b11111100;    // Enable all weak pull-up resistors on port C except
                        //    RC0 and RC1 to be used as I2C SCL and SDA
TRISA  = 0b00110000;    // Set RA4 and RA5 as inputs
ANSELA = 0b00110000;    // Set RA4 and RA5 to analog
TRISB  = 0b00110000;    // Set RB6 and RB7 as inputs
ANSELB = 0b11000000;    // Set RB6 and RB7 as analog
TRISC  = 0b11111011;    // Set RC0, RC1, RC3, RC4, RC5, RC6, and RC7 as inputs
ANSELC = 0b11111000;    // Set RC3, RC4, RC5, RC6, and RC7 as analog
TX2CKPPS   = 0b01100;   // Use RB4 for TX2
RX2DTPPS   = 0b01110;   // Use RB6 for RX2
SSP1CLKPPS = 0b10000;   // Use RC0 as SCL
SSP1DATPPS = 0b10001;   // Use RC1 as SDA
SSP1CON1 = 0b00100110;  // SSPEN enabled, WCOL no collision, SSPOV no overflow,
                        // CKP low hold, SSPM I2C slave 7-bit

SSP1CON2 = 0b00000000;  // ACKSTAT received, RCEN disabled, RSEN disabled, 
                        // ACKEN disabled, ACKDT acknowledge, SEN disabled, 
                        // GCEN disabled, PEN disabled

SSP1CON3 = 0b00000000;  // BOEN disabled, AHEN disabled, SBCDE disabled, 
                        // SDAHT 100 ns hold, ACKTIM ackseq, DHEN disabled, 
                        // PCIE disabled, SCIE disabled

SSP1STAT = 0x00;
SSP1BUF  = 0x00;
SSP1MSK  = 0xff;
SSP1ADD  = I2C_SLAVE_ADDR << 1;
PIR3bits.SSP1IF = 0;    // Clear the SSP Interrupt flag
PIE3bits.SSP1IE = 1;    // Enable SSP Interrupts
INTCONbits.GIE = 1;     // Enable global interrupts
INTCONbits.PEIE = 1;    // Enable peripheral interrupts

Answer 1

您可能有几个问题需要处理。

所有默认的 I2C 引脚也都具有模拟功能。确保与 I2C 引脚关联的 ANSB 或 ANSC 位设置为数字操作。

虽然上电复位为 I2C 输入引脚分配选择数据表默认值，但默认情况下 I2C 输出未分配给任何 GPIO 别针。您需要将 SCL 和 SDA 的 I2C 输出放置在正确的 PPS 映射寄存器中。

请注意，无论 I2C 是主设备还是从设备，输入和输出功能都应映射到同一引脚。

这将有助于编辑您的问题并发布您用于初始化 I2C 引脚和 PPS 映射寄存器的代码。

/*
 * File:   main.c
 *                             PIC16LF15354
 *                   +-------------:_:-------------+
 * 10K Pull-Up ->  1 : RE3/MCLR   ANB7/RX2/PGD/RB7 : 28 <> 
 *             <>  2 : RA0/ANA0   ANB6/TX2/PGC/RB6 : 27 <> RX2
 *             <>  3 : RA1/ANA1           ANB5/RB5 : 26 <>
 *             <>  4 : RA2/ANA2           ANB4/RB4 : 25 <> TX2
 *             <>  5 : RA3/ANA3           ANB3/RB3 : 24 <>
 *             <>  6 : RA4/ANA4      ANB2/SDA2/RB2 : 23 <>
 *             <>  7 : RA5/ANA5      ANB1/SCL2/RB1 : 22 <>
 *         GND ->  8 : VSS                ANB0/RB0 : 21 <>
 *             <>  9 : RA7/OSC1/ANA7           VDD : 20 <- 3v3
 *             <> 10 : RA6/OSC2/ANA6           VSS : 19 <- GND
 *        SCL1 <> 11 : RC0/ANC0       ANC7/RX1/RC7 : 18 <>
 *        SDA1 <> 12 : RC1/ANC1       ANC6/TX1/RC6 : 17 <>
 *             <> 13 : RC2/ANC2           ANC5/RC5 : 16 <> 
 *             <> 14 : RC3/SCL1/ANC3 ANC4/SDA1/RC4 : 15 <>
 *                   +-----------------------------:
 *                               DIP-28
 *
 * Created on January 4, 2019, 6:20 PM
 */


// PIC16LF15354 Configuration Bit Settings
#pragma config FEXTOSC = OFF    // External Oscillator mode selection bits (Oscillator not enabled)
#pragma config RSTOSC = HFINT32 // Power-up default value for COSC bits (HFINTOSC with OSCFRQ= 32 MHz and CDIV = 1:1)
#pragma config CLKOUTEN = OFF   // Clock Out Enable bit (CLKOUT function is disabled; i/o or oscillator function on OSC2)
#pragma config CSWEN = ON       // Clock Switch Enable bit (Writing to NOSC and NDIV is allowed)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enable bit (FSCM timer disabled)
#pragma config MCLRE = ON       // Master Clear Enable bit (MCLR pin is Master Clear function)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config LPBOREN = OFF    // Low-Power BOR enable bit (ULPBOR disabled)
#pragma config BOREN = OFF      // Brown-out reset enable bits (Brown-out reset disabled)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (VBOR) set to 1.9V on LF, and 2.45V on F Devices)
#pragma config ZCD = OFF        // Zero-cross detect disable (Zero-cross detect circuit is disabled at POR.)
#pragma config PPS1WAY = OFF    // Peripheral Pin Select one-way control (The PPSLOCK bit can be set and cleared repeatedly by software)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable bit (Stack Overflow or Underflow will cause a reset)
#pragma config WDTCPS = WDTCPS_31// WDT Period Select bits (Divider ratio 1:65536; software control of WDTPS)
#pragma config WDTE = SWDTEN    // WDT operating mode (WDT enabled/disabled by SWDTEN bit in WDTCON0)
#pragma config WDTCWS = WDTCWS_7// WDT Window Select bits (window always open (100%); software control; keyed access not required)
#pragma config WDTCCS = SC      // WDT input clock selector (Software Control)
#pragma config BBSIZE = BB512   // Boot Block Size Selection bits (512 words boot block size)
#pragma config BBEN = OFF       // Boot Block Enable bit (Boot Block disabled)
#pragma config SAFEN = OFF      // SAF Enable bit (SAF disabled)
#pragma config WRTAPP = OFF     // Application Block Write Protection bit (Application Block not write protected)
#pragma config WRTB = OFF       // Boot Block Write Protection bit (Boot Block not write protected)
#pragma config WRTC = OFF       // Configuration Register Write Protection bit (Configuration Register not write protected)
#pragma config WRTSAF = OFF     // Storage Area Flash Write Protection bit (SAF not write protected)
#pragma config LVP = OFF        // Low Voltage Programming Enable bit (High Voltage on MCLR/Vpp must be used for programming)
#pragma config CP = OFF         // UserNVM Program memory code protection bit (UserNVM code protection disabled)

#include <xc.h>

#define I2C_SLAVE_ADDR 0x00

void main(void) 
{
    WPUA   = 0b00111111;    // Enable all weak pull-up resistors on port A
    WPUB   = 0b11110000;    // Enable all weak pull-up resistors on port B
    WPUC   = 0b11111100;    // Enable all weak pull-up resistors on port C except
                            //    RC0 and RC1 to be used as I2C SCL and SDA
    TRISA  = 0b00110000;    // Set RA4 and RA5 as inputs
    ANSELA = 0b00110000;    // Set RA4 and RA5 to analog
    TRISB  = 0b00110000;    // Set RB6 and RB7 as inputs
    ANSELB = 0b11000000;    // Set RB6 and RB7 as analog
    TRISC  = 0b11111011;    // Set RC0, RC1, RC3, RC4, RC5, RC6, and RC7 as inputs
    ANSELC = 0b11111000;    // Set RC3, RC4, RC5, RC6, and RC7 as analog
#ifdef WRONG_WAY_TO_DO_PPS
    TX2CKPPS   = 0b01100;   // Use RB4 for TX2
    RX2DTPPS   = 0b01110;   // Use RB6 for RX2
    SSP1CLKPPS = 0b10000;   // Use RC0 as SCL
    SSP1DATPPS = 0b10001;   // Use RC1 as SDA
#else
    RB4PPS     = 0x11;      // Assign TX2 output  to RB4
    RX2DTPPS   = 0x0E;      // Assign RB6         to RX2 input
    RC0PPS     = 0x15;      // Assign SCL1 output to RC0
    SSP1CLKPPS = 0x10;      // Assign RC0         to SCL1 input
    RC1PPS     = 0x16;      // Assign SDA1 output to RC1
    SSP1DATPPS = 0x11;      // Assign RC1         to SDA1 input
#endif
    SSP1CON1 = 0b00100110;  // SSPEN enabled, WCOL no collision, SSPOV no overflow,
                            // CKP low hold, SSPM I2C slave 7-bit

    SSP1CON2 = 0b00000000;  // ACKSTAT received, RCEN disabled, RSEN disabled, 
                            // ACKEN disabled, ACKDT acknowledge, SEN disabled, 
                            // GCEN disabled, PEN disabled

    SSP1CON3 = 0b00000000;  // BOEN disabled, AHEN disabled, SBCDE disabled, 
                            // SDAHT 100 ns hold, ACKTIM ackseq, DHEN disabled, 
                            // PCIE disabled, SCIE disabled

    SSP1STAT = 0x00;
    SSP1BUF  = 0x00;
    SSP1MSK  = 0xff;
    SSP1ADD  = I2C_SLAVE_ADDR << 1;
    PIR3bits.SSP1IF = 0;    // Clear the SSP Interrupt flag
    PIE3bits.SSP1IE = 1;    // Enable SSP Interrupts
    INTCONbits.GIE = 1;     // Enable global interrupts
    INTCONbits.PEIE = 1;    // Enable peripheral interrupts
    /*
     * Embedded code never returns from main
     */
    for(;;)
    {

    }
}

PPS 设置正确，但我不知道 I2C 初始化代码是否正确。