STMicroelectronics STM32 Cortex-M3, Manual

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1 Intro
2 Electrocardiogram ( Ecg ) Signals
The Electrocardiogram (
Ecg
)
•
Ecg
: electrical manifestation of heart activity recorded
from the body surface
•
monitoring of heart rate
The
Ecg
signal can be recorded fairly easily with surface
electrodes placed on the limbs and/or the chest, see pages 6 – 16
below.
Josef Goette 2 2009
4 Peripherals
Figure 4.17: I
2
C Wiring
The third line is used when a slave want to tell the master something. An interrupt is generated
then.
4.15.1 Physical layer
I
2
C Definitions
•
Data can only be transmitted when the bus is not active.
•
As long as the clock is high, the data line is not allowed to change.
5
•
When no data are transmitted, SCL and SDA are high.
Figure 4.18:
I
2
C Communication Protocol
4.15.2 Communication Protocol
1. The data transfer starts with the start bit. The clock is High, data changes from High to Low,
see Figure 4.20
2. The slave address is transmitted.
3. The R/W Bit (see Figure 4.21 and 4.22 ) defines if data are read from the slave (R/W = 0) or
if data are written to the slave (R/W = 1).
5
A change of the data during a high clock is interpreted as a control command.
42 STM32 Cortex-M3 Tutorial