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drivers/bmp180: during init retry getting ID because it may fail #5589

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drivers/bmp180: during init retry getting ID because it may fail #5589

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10 changes: 6 additions & 4 deletions drivers/bmp180/bmp180.c
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Original file line number Diff line number Diff line change
Expand Up @@ -65,10 +65,12 @@ int bmp180_init(bmp180_t *dev, i2c_t i2c, uint8_t mode)
/* Acquire exclusive access */
i2c_acquire(dev->i2c_dev);

/* Check sensor ID */
char checkid;
i2c_write_byte(dev->i2c_dev, BMP180_ADDR, BMP180_REGISTER_ID);
i2c_read_reg(dev->i2c_dev, BMP180_ADDR, BMP180_REGISTER_ID, &checkid);
/* Check sensor ID (retry a few times, it may fail at first) */
char checkid = 0;
for (size_t ix = 0; checkid == 0 && ix < 3; ++ix) {
i2c_write_byte(dev->i2c_dev, BMP180_ADDR, BMP180_REGISTER_ID);
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during my tests, I also noticed that this line is not needed one can directly access the ID register with the next line.

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I created #5679. Can you give it a try ?

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For me it does not make a difference. It still fails when building with -O0.

But your changes seems to be correct. With the default -Os it works for me.

BTW. Why didn't you remove

i2c_write_byte(dev->i2c_dev, BMP180_ADDR, (char)BMP180_CALIBRATION_AC1);

It seems useless too.

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Sorry, forget about my last BTW (about leaving out the write_byte). It turns out it is necessary.

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Again.
The above mentioned i2c_write_byte still does not make sense. Why is it needed? I don't think it is. But if I leave it out I'm getting all zeroes for the calibration.

To solve that I need a delay between the BMP180_REGISTER_ID and the BMP180_CALIBRATION_AC1.

Here is a question to you. Can you try the following?

diff --git a/drivers/bmp180/bmp180.c b/drivers/bmp180/bmp180.c
index e772c3a..ad771cc 100644
--- a/drivers/bmp180/bmp180.c
+++ b/drivers/bmp180/bmp180.c
@@ -73,10 +73,10 @@ int bmp180_init(bmp180_t *dev, i2c_t i2c, uint8_t mode)
         i2c_release(dev->i2c_dev);
         return -1;
     }
+    xtimer_usleep(3);

     char buffer[22] = {0};
     /* Read calibration values, using contiguous register addresses */
-    i2c_write_byte(dev->i2c_dev, BMP180_ADDR, (char)BMP180_CALIBRATION_AC1);
     if (i2c_read_regs(dev->i2c_dev, BMP180_ADDR, BMP180_CALIBRATION_AC1, buffer, 22) < 0) {
         DEBUG("[Error] Cannot read calibration registers.\n");
         i2c_release(dev->i2c_dev);

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@keestux, I tried in #5679 and it indeed works better. Let me know if it's the same for you. We could then merge #5679 as a bug fix.

i2c_read_reg(dev->i2c_dev, BMP180_ADDR, BMP180_REGISTER_ID, &checkid);
}
if (checkid != 0x55) {
DEBUG("[Error] Wrong device ID\n");
return -1;
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