STM8 multi-byte I2C reads

Question

u8 i2c_read_register(u8 mem_address, u8 *data_read) { u8 temp = 0; u8 ack = 0; u8 device_address = (IQS_ADDR << 1); u8 polling_attempt = 0; // send address ack = i2c_send_byte(device_address); #ifdef POLLING while ((ack) && (polling_attempt < POLLING_ATTEMPTS)) { i2c_wait(); i2c_wait(); i2c_start(); ack = i2c_send_byte(device_address); polling_attempt++; } #endif if (!ack) { i2c_send_byte(mem_address); i2c_repeat_start(); device_address = (IQS_ADDR << 1) | 0x01; ack = i2c_send_byte(device_address); temp = i2c_read_byte(1); (*data_read) = temp; } return ack; }

Notes In order to read two Byes I need to call the function Like This:

i2c_read_register(DEBUGGING_EVENTS, &data_buffer[1], 2);

With (2) representing the Number of Bytes. But as the function stand it only takes two arguments not three.

The Memory Address that I'm trying to read always return two bytes, First byte for Events, and 2nd Bytes for movement, so I have to specify reading the two bytes in my function. — Chad
– Chad, Commented Aug 12, 2015 at 11:26
As suggested - call i2c_read_byte() with the two different addresses you are trying to read from. If this doesn't work, it implies that the device is expecting a multi-byte read and the data is not valid if this is not the case (you should already have seen this in the datasheet). In this case, try Googling "i2c multi-byte read" and "i2c repeated start condition". This info is normally included as a simple timing diagram in the datasheet too. — stefandz
– stefandz, Commented Aug 12, 2015 at 11:40
OK - so this is really about STM8 multi-byte reads. I haven't worked with STM8 parts before, but a quick Google on this brought up ST application note AN3281. That looks worth a read - but the fact I found something that quickly suggests you have not done much research on this. — stefandz
– stefandz, Commented Aug 12, 2015 at 12:07

rfkortekaas · Accepted Answer · 2015-08-12 16:19:04Z

1

In the software package for the stm8 Eval board is an example project which is using a serial eeprom which is able to read multiple bytes.

sEE example software

answered Aug 12, 2015 at 16:19

rfkortekaas

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\$\begingroup\$ Yes I do I have the file, as you may have noticed I already Have a function that was working but only for reading a single byte. So I only wanted to modify it to read two Bytes instead of writing a whole new Function. \$\endgroup\$

Chad
– Chad

2015-08-13 06:57:12 +00:00
Commented Aug 13, 2015 at 6:57

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Chad · Accepted Answer · 2015-08-12 15:49:05Z

After Hours of Trying to modify the Code I finally managed to get the Specified two Bytes from my i2c_read_register() Function.

u8 i2c_read_register(u8 register_address, u8 *data_read, u8 NumbOfBytes) { u8 i; u8 temp = 0; u8 ack = 0; u8 device_address = (IQS_ADDR << 1); u8 polling_attempt = 0; // send address ack = i2c_send_byte(device_address); #ifdef POLLING while ((ack) && (polling_attempt < POLLING_ATTEMPTS)) { i2c_wait(); i2c_wait(); i2c_start(); ack = i2c_send_byte(device_address); polling_attempt++; } #endif if (!ack) { i2c_send_byte(register_address); i2c_repeat_start(); device_address = (IQS_ADDR << 1) | 0x01; ack = i2c_send_byte(device_address); //temp = i2c_read_byte(1); //(*data_read) = temp; if(NumbOfBytes > 1) { for(i = 0; i < NumbOfBytes -1; i++) data_read[i] = i2c_read_byte(0); } data_read[i] = i2c_read_byte(1); } return ack; }

All That was needed, was to add a for Loop Incrementing the Number of Bytes to read as input by user with the u8 NumbOfBytes variable.

And you call the function Like This:

i2c_start(); i2c_read_register(DEBUGGING_EVENTS, &data_buffer[0], 2); i2c_stop(); events = data_buffer[0]; // Main Events 1st Byte movement = data_buffer[1]; // Debugging Events 2nd Byte

You might want to flag your own answer as correct, so that others know that this is now solved. — stefandz
– stefandz, Commented Aug 12, 2015 at 20:06
@ stefandz, Yes The u=rules says u have to wait for 48 Hours to Flag your own answer as solution. — Chad
– Chad, Commented Aug 13, 2015 at 6:48

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