Debug Interface - SimCom SIM800L Hardware Design

Module
Note: When Figure22, Figure 23 and Figure 24 are used for electrical level isolation, if customers use serial port to upgrade SW,
please note VDD_EXT has no voltage output during the upgrading process, LDO output could be used as VDD_EXT in the
figure, upgrading through USB port is recommended.
4.5.3

Debug Interface

SIM800L could achieve software debug function through USB interface. When powering on the module, connect
VBUS, USB_DP, USB_DN, and GND to PC, then install the driver following the prompts, a UART port could
be recognized by PC, customer could achieve the software Debug with this UART port.
SIMCom recommended the following connected diagram:
The TVS on USB data line should be less than 5pF, and traced by differential forms.
Note: please reserve the USB interface or test point for the further debugging
Table 11: VBUS operation voltage
Pin
VBUS
SIM800L(MT6261)_Hardware Design_V1.01
VDD_EXT
VDD_EXT
4.7K
RXD
Figure 24: RX level matching circuit
USB_VBUS
USB _ DN
USB _ DP
GND
Module
Figure 25: USB reference circuit
Min
4.3
DTE
VDD
4.7K
47K
TXD
VBUS
22 R
USB _ DN
22R
USB_DP
1uF
GND
Typ Max
5.0 7
31
Smart Machine Smart Decision
USB
Unit
V
2016-07-07