各位先進好

最近使用 PIC32MM0064GPM0028 撰寫 Slave 裝置

並使用 mcc 產生 I2C Slave 的 code

測試時使用 arduino due 作為 Master 端測試

當 Master write to Slave 的時候結果正常，多次寫入均沒問題

但當 Master read from Slave ，第一次 read 正確

但經過第一次 read 後，要再次下達 wirte 或read 請求時，address 發送後均得到 NACK 的回應

請問有人有過類似的經驗嗎?

或著建議觀察哪些 SRF 檢查 I2C 的狀態是否異常?

附件為測試時的 code，使用 I2C2 並確認有接上拉電阻

謝謝

附加檔案:

---

PIC32MM0064GPM0028_Sample_20180528.X.zip 大小: 223.51 KB; 下載次數: 49

您好,我遇到問題是,當master read時,master發送address時,都會有NACK回應,最後我在
"case I2C2_SLAVE_RECEIVED_DATA_DETECTED:"
最後面加上"I2C2_RELEASE_SCL_CLOCK_CONTROL_BIT = 1;"
就可以了,我也不確定,這是不是正確的解法.

Hi

我剛剛試著加上去

但好像沒有效果

剛剛在 Master Read from Slave 1byte 的資料後，觀看 I2CxSTAT

不知道會不會跟 RBF = 1 有關(此時Slave端已經收到Stop bit)

附加檔案:

---

  AfterMasterReadFromSlave.jpg (253.97 KB)

剛剛修改了一下 Code

在 mcc 產生的 i2c2.c 內的 switch case 中

將 case S_SLAVE_TRANSMIT_MODE: 的最後一段加上清除 I2C2bits.I2COV 的動作後

I2C 程式就能正常讀寫了

case S_SLAVE_TRANSMIT_MODE:

// this is the state where an ACK or NACK is expected
// to occur after the slave has placed data to the
// transmit register.

// if the transaction was ACK'ed, more data needs to be sent
// if the transaction was NACK'ed then we don't need to send
// more data
if (I2C2_ACKNOWLEDGE_STATUS_BIT == 0)
{
// prepare next data
I2C2_StatusCallback(I2C2_SLAVE_TRANSMIT_REQUEST_DETECTED);

// transmit more data
I2C2_TransmitProcess();

}
else //if (I2C2_ACKNOWLEDGE_STATUS_BIT == 1)
{
// no more data to be sent so we go to idle state
i2c2_slave_state = S_SLAVE_IDLE;
}

if( I2C2_RECEIVE_OVERFLOW_STATUS_BIT == true )
{
dummy = I2C2_RECEIVE_REG;
I2C2_RECEIVE_OVERFLOW_STATUS_CLR;
}

break;

不確定是什麼原因

在 Master 向 Slave 發起 read 請求後

RBF,I2COV 被設為 1，且直到 Read 結束後沒有被清除

導致後續 Master 發出 ADDRESS 請求，也不會收到 Slave 端的 ACK

目前翻 datasheet 也只翻到 RBF,I2COV 被設為 1 的原因

Overrun is indicated if either (or both):
•The buffer full bit, RBF (I2CxSTAT<1>), was set before the transfer was received
•The overflow bit, I2COV (I2CxSTAT<6>), was set before the transfer was received

一般在 Data Sheet 不會有詳細的說明，請參考:
PIC32 Family Reference Manual, Sect. 24 Inter-Integrated Circuit
http://ww1.microchip.com/downloads/en/DeviceDoc/61116F.pdf

依聚餐存氣的位元說明 I2COV: I2C Receive Overflow Status bit
1 =A byte is received while the I2CxRCV register is still holding the previous byte.
I2COV is a “don’t care” in Transmit mode. This bit must be cleared in software.
0 = No overflow

在 Figure 24-30:Slave Message 有時序圖說明。此外也提及:
Reading the I2CxRCV register clears the RBF bit. The I2COV bit is cleared by writing to a ‘0’ through software.