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Don't waste RAM in the low-level TWI Wire driver #520

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Don't waste RAM in the low-level TWI Wire driver #520

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18 changes: 3 additions & 15 deletions libraries/Wire/src/utility/twi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,7 @@ static volatile bool twi_do_reset_on_timeout = false; // reset the TWI register
static void (*twi_onSlaveTransmit)(void);
static void (*twi_onSlaveReceive)(uint8_t*, int);

static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH];
static uint8_t *twi_masterBuffer;
static volatile uint8_t twi_masterBufferIndex;
static volatile uint8_t twi_masterBufferLength;

Expand Down Expand Up @@ -158,8 +158,6 @@ void twi_setFrequency(uint32_t frequency)
*/
uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sendStop)
{
uint8_t i;

// ensure data will fit into buffer
if(TWI_BUFFER_LENGTH < length){
return 0;
Expand All @@ -179,6 +177,7 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen
twi_error = 0xFF;

// initialize buffer iteration vars
twi_masterBuffer = data;
twi_masterBufferIndex = 0;
twi_masterBufferLength = length-1; // This is not intuitive, read on...
// On receive, the previously configured ACK/NACK setting is transmitted in
Expand Down Expand Up @@ -226,11 +225,6 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen
length = twi_masterBufferIndex;
}

// copy twi buffer to data
for(i = 0; i < length; ++i){
data[i] = twi_masterBuffer[i];
}

return length;
}

Expand All @@ -252,8 +246,6 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen
*/
uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait, uint8_t sendStop)
{
uint8_t i;

// ensure data will fit into buffer
if(TWI_BUFFER_LENGTH < length){
return 1;
Expand All @@ -273,14 +265,10 @@ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait
twi_error = 0xFF;

// initialize buffer iteration vars
twi_masterBuffer = data;
twi_masterBufferIndex = 0;
twi_masterBufferLength = length;

// copy data to twi buffer
for(i = 0; i < length; ++i){
twi_masterBuffer[i] = data[i];
}

// build sla+w, slave device address + w bit
twi_slarw = TW_WRITE;
twi_slarw |= address << 1;
Expand Down