Make TWI_ReadPacket() use a repeated start condition rather than a full bus release...

[pub/lufa.git] / LUFA / Drivers / Peripheral / AVR8 / TWI_AVR8.c

diff --git a/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.c b/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.c
index d4f594f..d6db37d 100644 (file)
--- a/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.c
+++ b/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.c
@@ -97,34 +97,69 @@ uint8_t TWI_StartTransmission(const uint8_t SlaveAddress,
        }
 }
 
+bool TWI_SendByte(const uint8_t Byte)
+{
+       TWDR = Byte;
+       TWCR = ((1 << TWINT) | (1 << TWEN));
+       while (!(TWCR & (1 << TWINT)));
+
+       return ((TWSR & TW_STATUS_MASK) == TW_MT_DATA_ACK);
+}
+
+bool TWI_ReceiveByte(uint8_t* const Byte,
+                                        const bool LastByte)
+{
+       uint8_t TWCRMask;
+
+       if (LastByte)
+         TWCRMask = ((1 << TWINT) | (1 << TWEN));
+       else
+         TWCRMask = ((1 << TWINT) | (1 << TWEN) | (1 << TWEA));
+
+       TWCR = TWCRMask;
+       while (!(TWCR & (1 << TWINT)));
+       *Byte = TWDR;
+       
+       uint8_t Status = (TWSR & TW_STATUS_MASK);
+       
+       return ((LastByte) ? (Status == TW_MR_DATA_NACK) : (Status == TW_MR_DATA_ACK));
+}
+
 uint8_t TWI_ReadPacket(const uint8_t SlaveAddress,
                        const uint8_t TimeoutMS,
                        const uint8_t* InternalAddress,
-                       const uint8_t InternalAddressLen,
+                       uint8_t InternalAddressLen,
                        uint8_t* Buffer,
                        uint8_t Length)
 {
        uint8_t ErrorCode;
        
-       if ((ErrorCode = TWI_WritePacket(SlaveAddress, TimeoutMS, InternalAddress, InternalAddressLen,
-                                        NULL, 0)) != TWI_ERROR_NoError)
-       {
-               return ErrorCode;
-       }
-
-       if ((ErrorCode = TWI_StartTransmission((SlaveAddress & TWI_DEVICE_ADDRESS_MASK) | TWI_ADDRESS_READ,
-                                                                                  TimeoutMS)) == TWI_ERROR_NoError)
+       if ((ErrorCode = TWI_StartTransmission((SlaveAddress & TWI_DEVICE_ADDRESS_MASK) | TWI_ADDRESS_WRITE,
+                                              TimeoutMS)) == TWI_ERROR_NoError)
        {
-               while (Length--)
+               while (InternalAddressLen--)
                {
-                       if (!(TWI_ReceiveByte(Buffer++, (Length == 1))))
-                       {
+                       if (!(TWI_SendByte(*(InternalAddress++))))
+                       {                               
                                ErrorCode = TWI_ERROR_SlaveNAK;
                                break;
                        }
                }
                
-               TWI_StopTransmission();
+               if ((ErrorCode = TWI_StartTransmission((SlaveAddress & TWI_DEVICE_ADDRESS_MASK) | TWI_ADDRESS_READ,
+                                                                                          TimeoutMS)) == TWI_ERROR_NoError)
+               {
+                       while (Length--)
+                       {
+                               if (!(TWI_ReceiveByte(Buffer++, (Length == 0))))
+                               {
+                                       ErrorCode = TWI_ERROR_SlaveNAK;
+                                       break;
+                               }
+                       }
+                       
+                       TWI_StopTransmission();
+               }
        }
        
        return ErrorCode;
@@ -145,7 +180,7 @@ uint8_t TWI_WritePacket(const uint8_t SlaveAddress,
                while (InternalAddressLen--)
                {
                        if (!(TWI_SendByte(*(InternalAddress++))))
-                       {
+                       {                               
                                ErrorCode = TWI_ERROR_SlaveNAK;
                                break;
                        }