{"id":1735,"date":"2019-03-01T22:17:17","date_gmt":"2019-03-01T21:17:17","guid":{"rendered":"http:\/\/wildlab.org\/?p=1735"},"modified":"2021-06-22T09:57:22","modified_gmt":"2021-06-22T08:57:22","slug":"stm32-i2c-scanner","status":"publish","type":"post","link":"https:\/\/wildlab.org\/index.php\/2019\/03\/01\/stm32-i2c-scanner\/","title":{"rendered":"STM32 I2C Scanner"},"content":{"rendered":"

I2C scanner for STM32f10x<\/a> series<\/h2>\n

I2C scanner is fairly simple, yet fast and effective way to find whatever device you put onto I2C bus. Some devices (boards) comes with clear designation on the PCB, some with misleading designation – address is shifted to the left, so for example OLED<\/a> display typical address is 0x3C\/0x3D (depends of address selector jumper), but shifted to the left by 1 bit is 0x78 or 0x7A respectively. They made it as if zero bit is inserted at LSB place so that you ‘just’ send it as-is. But that is bad practice. Rather make your own shifting routine and insert 1 or 0, whether you want to read or write at this address.<\/p>\n

Example:<\/p>\n

\"scanner\"<\/a>The code is even simpler:<\/p>\n

\/* Part of the code, will not work alone !!! *\/\r\n\r\nvoid twiScan(void)\r\n{\t\tint a=0; \r\n\t \tfor (uint8_t i=0;i<128;i++)\r\n   {\r\n\t\t\tI2C1->CR1 |= I2C_CR1_START;\r\n\t\t\twhile(!(I2C1->SR1 & I2C_SR1_SB));\r\n\t\t\tI2C1->DR=(i<<1|0); \r\n\t\t\twhile(!(I2C1->SR1)|!(I2C1->SR2)){}; \r\n\t\t\tI2C1->CR1 |= I2C_CR1_STOP; \r\n\t\t\tdelay(100);\/\/minium wait time is 40 uS, but for sure, leave it 100 uS\r\n\t\t\ta=(I2C1->SR1&I2C_SR1_ADDR);\r\n\t\t\tif (a==2)\r\n\t\t {\r\n\t\t\t\tprintMsg(\"Found I2C device at adress 0x%X (hexadecimal), or %d (decimal)\\n\",i,i);\r\n\t\t }\r\n\t }\r\n}<\/pre>\n
Whole thing scan all 127 addresses in 45 mS.<\/p>\n
Here is how looks whole packet with six addresses found. After each address found, there is 5.5 mS delay until timeout.:<\/p>\n
\"scanner\"<\/a>
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