10.3. More information
10.3.1. UART
• The data sent to the UART is buffered in the Proteus-e up to a maximum payload of
243 Bytes. When no new byte was received for 20 ms, the data will be transmitted
by radio to the connected Bluetooth
®
LE device. If the data is larger than the MPS
of the connection, the data is sent via radio in several packets, with one packet per
connection interval.
• To enable a fast transmission of data packets a large MPS of the Bluetooth
®
LE connec-
tion is helpful. The Proteus-e supports up to 243 Bytes Bluetooth
®
LE packet payload
(corresponding to a MTU of 247 Bytes), which may be negotiated by the central device
(using a MTU request). If no MTU request is requested by the connecting central de-
vice the value of 19 Bytes payload per Bluetooth
®
LE packet and connection interval
as given by the Bluetooth
®
4.0 standard is used (compatibility mode to Bluetooth
®
LE
4.0 devices).
• The pin
can be used as a kind of flow control for the data transmission during
the transparent mode. By default the pin level is LOW. As soon as the 20ms timeout
was detected or too much data was received via UART, the pin switches to HIGH and
data transmission starts via Bluetooth
®
LE. The pin switches LOW again, as soon
as Bluetooth
®
LE data transmission has finished and the transmission of new data is
feasible again. In case the pin is HIGH, no more data is accepted on the UART.
Figure 12: Switch of the
pin when transmitting data
To use the signal on the
pin as flow control on the host controller side, we recommend
to use an OR gate to combine the
and
pins’ signals.
Proteus-e reference manual version 0.3
© November 2021
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