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FEZ Cream on Raspberry pi


#1

Hello,
If I look on schematic or code for FEZ Cream, it appears 4 devices on i2c bus:
[ul]0x23 Virtual IOs 1[/ul]
[ul]0x25 Virtual IOs 2[/ul]
[ul]0x48 Analog to digital[/ul]
[ul]0x7f PWM[/ul]

But if I run i2cdetect on my rpi (raspbian os).
I can see 4 address: 0x23 (seems ok), 0x25 (seems ok), 0x48 (seems ok), 0x70 (shouldn’t be 0x7f ???)

And why i2cdetect seems only able to detect i2c device from 0x03 to 0x77, as device can go from 0x00 and 0x7f ?


#2

@ Bauland - 7 bit bytes?


#3

7 bit address is from 0x00 to 0x7f isn’t it ?


#4

see : http://www.totalphase.com/support/articles/200349176-7-bit-8-bit-and-10-bit-I2C-Slave-Addressing#7bit

Standard 7-bit I2C addresses have a rw bit in the LSB and six bits of address in A1 through A6. The high-order bit is not used.


#5

… in A0 to A6 following your nice document ! So if pwm address is 0x7f how to access it ?


#6

Looking at the Fez Cream schematic, and this document : https://cdn-shop.adafruit.com/datasheets/PCA9685.pdf section 7.1.1, it looks to me like the address is set to 0x7e (not 0x7f - remember that A0-A6 actually occupy bits 1-7). If i2cdetect sees it at 0x70, then I would try that addr first, and if that doesn’t work, then try 0x7e.

Let us know which one works.