Somewhere in the driver (I don't recall where exactly, should be in nrf i2c driver), there is a limit on the amount of data that you can transmit via I2C. Or rather, the driver functions somewhere use a uint8_t size (so I guess the limit is 256 even though I used 258 in below, not sure why anymore). Best to step through the code to verify where the amount of transmit or receive bytes is clipped.
Let me know if that helps. I don't have any hardware available right now so I can't confirm anything.
#define MAX_I2C_TX_SIZE 258
uint8_t writeBuf_pd[MAX_I2C_TX_SIZE];
#define MAX_I2C_RX_SIZE 128
uint8_t readBuf_pd[MAX_I2C_RX_SIZE];
uint8_t VL53L5CX_i2c_writeMultipleBytes(uint16_t registerAddress, uint8_t *buffer, uint16_t bufferSize)
{
// Chunk I2C transactions into limit of 32 bytes (or wireMaxPacketSize)
uint8_t i2cError = 0;
uint32_t bytesToSend = bufferSize;
uint16_t offset = 0;
while (bytesToSend > 0 && i2cError == 0)
{
uint32_t len = bytesToSend;
if (len > (MAX_I2C_TX_SIZE - 2)) // Allow 2 byte for register address
len = (MAX_I2C_TX_SIZE - 2);
writeBuf_pd[0] = registerAddress>>8;
writeBuf_pd[1] = registerAddress & 0xff;
memcpy(&(writeBuf_pd[2]), &(buffer[offset]), len);
i2cError = i2c_write(dev_i2c, writeBuf_pd, len+2, VL53L5_DEFAULT_I2C_ADDR);
bytesToSend -= len;
registerAddress += len; // Move register address forward
offset += len;
}
if(i2cError) {
printk("i2c multiwrite error %d\n", i2cError);
}
return (i2cError);
}
uint8_t VL53L5CX_i2c_readMultipleBytes(uint16_t registerAddress, uint8_t *buffer, uint16_t bufferSize) {
int i2cError = 0;
uint32_t bytesToReceive = bufferSize;
uint32_t offset = 0;
while (bytesToReceive > 0 && i2cError == 0)
{
uint16_t len = bytesToReceive;
if ( len > MAX_I2C_RX_SIZE) {
//printk("reduced %d bufferSize ... %d\n", bufferSize, len);
len = MAX_I2C_RX_SIZE;
}
writeBuf_pd[0] = registerAddress>>8;
writeBuf_pd[1] = registerAddress & 0xff;
i2cError = aggr_i2c_write_read(dev_i2c, VL53L5_DEFAULT_I2C_ADDR, writeBuf_pd, 2, &buffer[offset], len);
offset += len;
registerAddress += len;
bytesToReceive -= len;
if(i2cError) {
printk("i2c multiread error %d\n", i2cError);
}
}
return (0); // Success
}
