# \[Solved\] Unable to read I2C data from PiGlow with Raspberry Pi **URL:** \ **Category:** Support\ **Created:** [January 30, 2016, 10:35am UTC](https://forums.pimoroni.com/t/solved-unable-to-read-i2c-data-from-piglow-with-raspberry-pi/1711 "2016-01-30T10:35:36Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![lategoodbye](https://avatars.discourse-cdn.com/v4/letter/l/a8b319/32.png) [@lategoodbye](https://forums.pimoroni.com/u/lategoodbye)\ **Post date:** [January 30, 2016, 10:35am UTC](https://forums.pimoroni.com/t/solved-unable-to-read-i2c-data-from-piglow-with-raspberry-pi/1711/1 "2016-01-30T10:35:36Z")
Hi, i’m using a Raspberry Pi B (rev 1). I have connected a PiGlow to the P1 Header. The I2C bus clock is set to 100 kHz. Writing I2C data to the PiGlow works fine, but reading doesn’t work. ``` > i2cdetect -y 0 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- -- > i2cdetect -q -y 0 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- 54 -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- -- ``` Why is the SN3218 not detected with the first command? Is it possible to read the I2C register from SN3218? Thanks in advance ---
**Author:** ![gadgetoid](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/gadgetoid/32/13_2.png) [@gadgetoid](https://forums.pimoroni.com/u/gadgetoid)\ **Post date:** [January 30, 2016, 1:24pm UTC](https://forums.pimoroni.com/t/solved-unable-to-read-i2c-data-from-piglow-with-raspberry-pi/1711/2 "2016-01-30T13:24:35Z")
The SN3218 is a write-only device, it’s impossible to read from it. There wouldn’t be anything there worth reading anyway- except, presumably, the LED states you’ve just written to it which you’d already know! :D ---
**Author:** ![lategoodbye](https://avatars.discourse-cdn.com/v4/letter/l/a8b319/32.png) [@lategoodbye](https://forums.pimoroni.com/u/lategoodbye)\ **Post date:** [January 30, 2016, 4:09pm UTC](https://forums.pimoroni.com/t/solved-unable-to-read-i2c-data-from-piglow-with-raspberry-pi/1711/3 "2016-01-30T16:09:33Z")
Thank you, i skipped this sentence in the datasheet. Shame on me.