MOTG-RS232
Description
RS232 is a standard communication port for various industries and networking equipment. However, most of the microcontrollers do not facilitate direct RS232 communication as they do not support RS232 voltage levels.
MOTG-RS232 provides a low-power, high speed and low-cost solution for incorporating RS232 serial communication into your design.
Features
- Level conversion using ST232CDR IC by ST
- Supports both 3.3V and 5V power supply
- Up to 400kbps data rate
- ±25V input levels
- 300 µA supply current
- 6 V/µs minimum slew rate
- Supports 2-wire 3.3V/5V TTL UART interface (the logic depends on the supply)
Before Getting Started
Out of the box, the chipset's UART pins are not connected to the UMI of the MOTG.
MOTG-RS232 hardware allows the UART pins to be connected to either TX, RX or GPIO1, GPIO2 of the UMI. This is could be achieved by shorting the respective sides of solder bridges SB1 and SB2 using a solder blob and a soldering iron. This is done by the User.
Unless the designer intends to use two UART MOTGs on a gen4-MOTG-AC2 or gen4-MOTG-AC4 board, the UART pins should be directed to TX, RX of the UMI as shown above.
When two UART MOTGs are being used on a gen4-MOTG-AC2 or gen4-MOTG-AC4 board, the UART pins of one of the MOTGs should be diverted to GPIO1 and GPIO2 of the UMI, as shown below. This prevents both MOTGs from using the same pins of the gen4 display module for UART communication.
Chipset Features
MOTG-RS232 carries the ST3232, low-power RS232 driver and receiver IC. The datasheet for the ST3232 is available from the https://www.st.com/ website.
Pins and Solder Bridges
Pin Description
| Pin | Symbol | Description |
|---|---|---|
| 1 | 3.3V | 3.3V Input Supply |
| 2 | GND | Supply Ground |
| 3 | RX | Asynchronous Serial Receive Pin |
| 4 | TX | Asynchronous Serial Transmit Pin |
| 5 | N/C | Not Connected |
| 6 | N/C | Not Connected |
| 7 | N/C | Not Connected |
| 8 | GPIO2 | RX Bypass Pin |
| 9 | GPIO1 | TX Bypass Pin |
| 10 | N/C | Not Connected |
| 11 | N/C | Not Connected |
| 12 | N/C | Not Connected |
| 13 | N/C | Not Connected |
| 14 | N/C | Not Connected |
| 15 | GND | Supply Ground |
| 16 | 5.0V | 5V Input Supply |
Note
The designer can choose if the UART pins of the MOTG should be connected to either TX, RX or GPIO1, GPIO2 of the UMI. This could be achieved by shorting the respective sides of solder bridges SB1 and SB2. This is discussed in detail in Before Getting Started.
Solder Bridge Description
The MOTG-RS232 also has four solder bridges. The functionality of those solder bridges is described in the table below. These are soldered by the User.
| Solder Bridge | Description |
|---|---|
| SB1 | Short SB1 for 5.0V input supply |
| SB2 | Short SB2 for 3.3V input supply |
| SB3 | TX selector |
| SB4 | RX Selector |
The MOTG-RS232 supports both 3.3V and 5V supply. The preferred supply voltage could be chosen by shorting the appropriate solder bridge.
Mechanical Views
Schematic Details
Specifications
Recommended Operating Conditions
| Parameter | Conditions | Min | Typ | Max | Units |
|---|---|---|---|---|---|
| Supply Voltage (VCC) | 3.3 | 5.0 | 5.0 | V | |
| Operating Temperature | 0.0 | -- | 70.0 | °C | |
| Input Low Voltage (VIL) | All pins | -0.3 | -- | 0.3*VCC | V |
| Input High Voltage (VIH) | All pins | 0.7*VCC | -- | VCC+0.3 | V |
Global Characteristics Based on Operating Conditions
| Parameter | Conditions | Min | Typ | Max | Units |
|---|---|---|---|---|---|
| Supply Current (ICC) | VCC = 5.0V, Audio Playing | 30.0 | -- | 300.0 | mA |
| Standby Current | VCC = 5.0V | -- | 20.0 | -- | uA |
| Output Low Voltage (VOL) | -- | -- | 0.3 | V | |
| Output High Voltage (VOH) | 2.7 | -- | VCC | V |
Revision History
Hardware Revision
| Revision Number | Date | Description |
|---|---|---|
| 1.1 | 23/09/2016 | Initial Public Release version |
Datasheet Revision
| Revision Number | Date | Description |
|---|---|---|
| 1.8 | 06/01/2023 | Modified datasheet for web-based documentation |