The E32-TTL-100 SX1278 LoRA Module

I managed to grab one of those LoRa modules that litter the market today. Mine’s a E32-TTL-100 module which is said to be based on Semtech’s SX1278. Here’s the specifications for the module:

  • Module size:21*36mm
  • Antenna type:Standard SMA antenna (FREE)
  • Power supply:2.3V-5.5V DC
  • Communication level:5.2V(max)
  • Transmission distance:3000m(max)
  • Maximum power:2dB(100mW)
  • Air rates:2.4Kbps
  • Emission current:130mA @ 100mW
  • Receiving current:13.5mA @ Mode 0, Mode 1
  • Sleep Current:2.0uA(M1=1,M1=0)
  • Emission length:256 Byte
  • Receive length:256 Byte
  • Communication Interface:UART
  • RSSI support:Yes
  • Working frequency:410MHz-441MHz(Default 433MHz)
  • Operating temperature:-30?~+85?
  • Receiver sensitivity:-130dBm @ 1.2Kbps

A range of 3km! I doubt this is possible for non-LOS (line of sight) but let’s see.

The module has 7 pins as shown:

E32-TTL-100 SX1278 LoRa Module

It’s UART-based so I think RXD, TXD (and of course VCC and GND) are self-explanatory. Let me try to explain the M0, M1, and AUX pins.

Configuring Modes

It turns out, M0 and M1 are used to set the modes of the module. There are four modes: normal, wake up, power-saving and sleep. Here’s a useful table:

Mode M1 M0 Explanation
Normal 0 0 UART and wireless channel is good to go
Wake-Up 0 1 Same as normal but a preamble code is added to transmitted data for waking-up the receiver.
Power-Saving 1 0 UART is disable and wireless is on WOR(wake on radio) mode which means the device will turn on when there is data to be received. Transmission is not allowed.
Sleep 1 1 Used in setting parameters. Transmitting and receiving disabled.

The AUX Pin

The AUX pin serves as a flag for checking if the data has been sent or when data have been received. It’s also used to check if the module is still in self-check procedure which happens during power-on and exit from sleep mode.

When the module is idle, the AUX pin stays high. If there is data is to be sent, the AUX pin stays low 2-3 ms prior to the data being sent to the transmit buffer. The AUX pin goes back to high if the transmit buffer is clear (i.e., the data has been sent wirelessly). Similarly, the AUX pin goes low when there is data on the receive buffer.

The logic states of AUX pin are summarized below:

Parameter Setting

As mentioned, when the module is in sleep mode (M0=M1=1), we can change some options like baud rate, UART format, etc. The commands for changing parameters must be sent using 9600 baud, 8N1.

The format for changing parameters is : 0xC0/0xC2 ADDH ADDL SPED CHAN OPTION. When you want the parameters to be saved to EEPROM, use 0xC0. Otherwise, use 0xC2. The rest are bytes with the following possible values:

Item Description Notes
ADDH Module high address byte (00h by default)
ADDL Module low address byte (00h by default)
SPED UART Baud Rate and Air Data Rate See bit descriptions below.
CHAN Operating Frequency (0x00 to 0xFF corresponding to 410 to 441 MHz. Default is 0x17 – 433 MHz)
OPTION Other options See bit descriptions below.

SPED Bit Descriptions

Bit 7 and 6 Bit 5, 4, 3 Bit 2, 1, 0
UART Parity UART Baud Rate Air Data Rate
00：8N1（default）
01：8O1
10：8E1
11：8N1（equal to 00）		 000：1200bps001：2400bps

010：4800bps

011：9600bps（Default）

100：19200bps

101：38400bps

110：57600bps

111：115200bps

 000：0.3kbps001：1.2kbps

010：2.4kbps（Default）

011：4.8kbps

100：9.6kbps

101：19.2kbps

110：19.2kbps(equal to 101)

111：19.2kbps(equal to 101)

OPTION Bit Descriptions

Bit 7 Bit 6 Bit 5,4,3 Bit 2 Bit 1 and 0
Fixed Transmission I/O Drive Mode Wireless Wake-up Time FEC (Forward Error Correction) Switch Transmission Power
0: transparent transmission (default)1: fixed transmission (first three bytes can be used as high/low address and channel) 0: TXD, RXD, AUX are open-collectors1: TXD, RXD, AUX are push-pulls/pull-ups 000：250ms（default）001：500ms

010：750ms

011：1000ms

100：1250ms

101：1500ms

110：1750ms

111：2000ms

）

 0：Turn off FEC1：Turn on FEC（Default） 00： 20dBm（Default）01： 17dBm

10： 14dBm

11： 10dBm

So for example, you want to change the UART baud rate to 115200, 8N1 mode, air data rate to 19.2kbps, use the default 433 MHz operating frequency, fixed transmission mode, push-pull pins, 250 ms wake-up time, FEC on, and 20 dBm transmission power. Set M0 and M1 and send the following data through UART:

For reading the current options, send the commands:

This is for reading the version number:

And for resetting the module:

Bob Chan has created an example sketch for using the E32-100 LoRa module with the Arduino. The library is available at his github repository. His library allows you to change parameters as I have discussed.

To use the above library, follow this connection:

UNO/NANO(5V MODE) E32-TTL-100
D7 M0
D8 M1
A0 AUX
D10(Rx) 4.7k Ohm Tx
D11(Tx) 4.7k Ohm Rx

Applications

I hope you found this tutorial useful. If you have questions, kindly drop a comment below.

References: