Serial Interface
3-Wire Serial Interface
The data serial interface is an RS-232 interface through which RockBLOCK Plus and your host controller transfer commands, responses, and SBD (Short Burst Data) message data. Within this setup, RockBLOCK functions as DCE (Data Communication Equipment), and the FA (Field Application) acts as DTE (Data Terminal Equipment).
🚧 TX/RX Labeling
- TXD is an INPUT to the RockBLOCK.
- RXD is an OUTPUT from the RockBLOCK.
Additionally, the Ground (GND) connection plays a critical role:
- Ground (GND) serves as the common electrical return path and a reference point for the TX and RX signals, stabilizing the data transfer by reducing noise and ensuring signal integrity.
RockBLOCK 9602/9603 models operate using the same interface at 3.3V digital signal levels (LVTTL), and are 5V tolerant. If RS-232 voltage levels are required for compatibility with certain host controllers, an LVTTL to RS-232 level shifter must be included in the setup.
📘 Arduino Mega 2560
The Arduino Mega works with 5v level (TTL). The RockBLOCK is 5V tolerant and so no level-shifter is required.
RockBLOCK Plus Serial interface voltage levels
| Parameter | Value |
|---|---|
| Tx Low Maximum | -0.5V |
| Tx High Minimum | 0.5V |
| Rx Input Low Threshold | -0.5V |
| Rx Input High Threshold | 0.5V |
| Absolute maximum | 32.0V |
RockBLOCK 9602/9603 Serial interface voltage levels
| Parameter | Value |
|---|---|
| Tx Low Maximum | 0.6V |
| Tx High Minimum | 3.0V |
| Rx Input Low Threshold | 0.6V |
| Rx Input High Threshold | 3.0V |
| Absolute maximum | 5.0V |
The RockBLOCK 9602/9603 is 5v tolerant LVTTL, so as such the logic threshold is more like 2.4v as normal.
| Min | Max | |
|---|---|---|
| VOH | 2.4v | approx 3.3v |
| VOL | approx 0v | 0.4v |
| VIH | 2.0v | 5.5v |
| VIL | -0.3v | 0.8v |
Baud Rate
Host controllers connecting to RockBLOCK should be configured to the baud rate settings in the table below.
| Setting | Value |
|---|---|
| Baud Rate | 19200 |
| Data Bits | 8 |
| Parity | None (N) |
| Stop Bits | 1 |
You are advised not to change the baud rate so the RockBLOCK uses a reliable, fixed baud rate. Automatic baud rate adjustment settings are not supported.
Flow control
❗️ It is strongly recommended to use RockBLOCK with flow control disabled.
The flow control setting can be set by AT commands. RockBLOCK has flow control disabled during manufacture, but should the device be reset to defaults then the following commands will disable flow control:
/* Issue AT command */
AT\r
/* Receive response */
OK\r
/* Disable Flow Control */
AT&K0\r
/* Receive response */
OK\r
/* Save configuration in non-volatile memory */
AT&W0\r
/* Receive response */
OK\r