du mußt beide leitungen des busses mit jeweils einem widerstand auf +5V legen. ich arbeite schon immer mit 1K pullup und bisher laufen die ca. 100 displays ohne probleme (kabellänge 1.5-2.3m)

die spezifikation sagt:
Zitat Zitat von THE I 2C-BUS SPECIFICATION
VERSION 2.1
Philips Semiconductors
JANUARY 2000
16.1 Maximum and minimum values of resistors Rp
and Rs for Standard-mode I2C-bus devices
For Standard-mode I2C-bus systems, the values of
resistors Rp and Rs in Fig.33 depend on the following
parameters:
· Supply voltage
· Bus capacitance
· Number of connected devices (input current + leakage
current).
The supply voltage limits the minimum value of resistor Rp
due to the specified minimum sink current of 3 mA at
VOLmax = 0.4 V for the output stages. VDD as a function of
Rp min is shown in Fig.37. The required noise margin of
0.1VDD for the LOW level, limits the maximum value of Rs.
Rs max as a function of Rp is shown in Fig.38.
The bus capacitance is the total capacitance of wire,
connections and pins. This capacitance limits the
maximum value of Rp due to the specified rise time. Fig.39
shows Rp max as a function of bus capacitance.
The maximum HIGH level input current of each
input/output connection has a specified maximum value of
10 mA. Due to the required noise margin of 0.2 VDD for the
HIGH level, this input current limits the maximum value of
Rp. This limit depends on VDD. The total HIGH level input
current is shown as a function of Rp max in Fig.40.