---
title: "HAT LTE A7670G"
space: "HATs"
url: "https://docs.modbee.org/hats/hat-lte"
updated: "2026-10-25"
---

# ModBee Hat – LTE (A7670G)

![ModBee Hat LTE](/files/gitimg-114be340b1fd89224ce508a10fd044675850403e.webp)

LTE Cat-1 cellular hat for the [ModBee Node-UIO](https://github.com/mod-bee/modbee-node-uio), built around the SIMCom A7670G. It provides 4G LTE Cat-1 with GSM/GPRS/EDGE fallback, for sites without Wi-Fi that need more bandwidth than Cat-M1 or NB-IoT.

The Node-UIO talks to the module with AT commands over UART0. A USB-C port on the hat gives a PC direct access to the module.

## Module

Figures from SIMCom's A7670G module specification.

| Parameter | Value |
| --- | --- |
| Networks | LTE Cat-1, GSM/GPRS/EDGE |
| LTE-FDD bands | B1/2/3/4/5/7/8/12/13/18/19/20/25/26/28/66 |
| LTE-TDD bands | B38/39/40/41 |
| GSM bands | 850/900/1800/1900 MHz |
| Peak data rate | LTE 10 Mbps down / 5 Mbps up; EDGE 236.8 kbps; GPRS 85.6 kbps |
| Supply (VBAT) | 3.4–4.2 V, 3.8 V typical. The hat supplies 3.6 V |
| SIM | 1.8 V / 3 V |
| Logic level | 1.8 V. The hat level-shifts it to 3.3 V |
| Package | LCC + LGA, 24 × 24 × 2.4 mm |
| Operating temperature | −40 to +85 °C |

Network and band support depends on your carrier and country. Check that your SIM and carrier support LTE on the bands above. Some carriers no longer run 2G.

### GNSS

The hat has a GPS antenna connector wired to the module's GNSS pins. GNSS works only if the fitted module variant includes a GNSS receiver. SIMCom's A7670G specification doesn't list GNSS, so check the exact part number and suffix with your supplier if you need positioning.

## Board features

- **Power**: GPIO9 high switches the hat's 3.3 V rail on through a P-channel MOSFET. JP1 bypasses the switch. A buck-boost converter (U1) makes the module's 3.6 V supply from that rail.
- **Power key**: GPIO10 drives the module's PWRKEY through a transistor. GPIO10 high pulls PWRKEY low. The **PWR** button (SW1) does the same by hand.
- **UART**: the module's main UART connects to the Node-UIO's U0RX/U0TX (GPIO44/GPIO43) through MOSFET level shifters, 3.3 V to 1.8 V.
- **USB-C** (USB 2.0) connects straight to the module's USB, with ESD protection. Use it for AT commands from a PC and for module firmware updates. USB doesn't power the module, so the hat must be powered from the Node-UIO.
- **Buttons**: **BOOT** (SW2) pulls USB_BOOT high for USB firmware download. **RESET** (SW3) resets the module.
- **Nano SIM** holder.
- **Antennas**: two IPEX (U.FL) connectors, **LTE** and **GPS**. The GPS connector supplies 3.3 V bias for an active GNSS antenna.
- **LEDs**: **PWR** (hat powered), **STS** (module STATUS), **LTE** (module NETLIGHT).

The module's audio, camera, LCD, SPI, I2C and keypad interfaces are not connected on this hat.

## Connections

The hat headers J1 and J2 follow the common [hat connector pinout](/hats#hat-connector). This hat uses:

| Signal | ESP32-S3 | Function |
| --- | --- | --- |
| +3.3V, GND | – | Hat supply |
| GPIO9 | GPIO9 | Hat power enable (high = on) |
| GPIO10 | GPIO10 | PWRKEY (high = key pressed) |
| U0RX | GPIO44 | Module TXD → Node-UIO |
| U0TX | GPIO43 | Node-UIO → module RXD |

Only one cellular hat can be fitted. The CAT and LTE hats both use UART0 and GPIO10.

## Power key and LEDs

Timings from SIMCom's A7670 series hardware design. Check them against the document for your module revision.

- **On**: pulse PWRKEY low (GPIO10 high). The typical pulse is 50 ms. The example below uses 500 ms, well short of the 2.5 s power-off time. The UART is ready about 11 s later.
- **Off**: hold PWRKEY low for at least 2.5 s, or send `AT+CPOF`.

| LED | Meaning |
| --- | --- |
| PWR | Hat 3.3 V rail is on |
| STS | On when the module is powered and initialised |
| LTE | LTE: steady on while searching, 200 ms on/off when registered or transferring data. 2G: 800 ms on/off when registered, 200 ms on/off during data. Off: powered down or asleep |

## Getting started

1. With power off, insert a nano SIM and connect the LTE antenna.
2. Fit the hat to the Node-UIO with stacking headers.
3. Power the hat and press PWRKEY from your sketch:

```cpp
#include <Arduino.h>

constexpr int HAT_POWER = 9;   // high = hat powered
constexpr int PWRKEY    = 10;  // high = PWRKEY pressed
constexpr int MODEM_RX  = 44;  // U0RX
constexpr int MODEM_TX  = 43;  // U0TX

// UART0. Log over native USB so UART0 is free for the modem.
HardwareSerial modem(0);

void setup() {
  pinMode(PWRKEY, OUTPUT);
  digitalWrite(PWRKEY, LOW);
  pinMode(HAT_POWER, OUTPUT);
  digitalWrite(HAT_POWER, HIGH);
  delay(1000);

  digitalWrite(PWRKEY, HIGH);
  delay(500);
  digitalWrite(PWRKEY, LOW);

  modem.begin(115200, SERIAL_8N1, MODEM_RX, MODEM_TX);
  delay(12000);
  modem.println("AT");
}
```

4. Check the module answers `OK`, then set up the network, for example:
   - `AT+CPIN?`: SIM ready
   - `AT+CNMP=38`: LTE only (`2` = automatic)
   - `AT+CGDCONT=1,"IP","your.apn"`: set your carrier's APN
   - `AT+CSQ`, `AT+CEREG?`: signal strength and registration

The A76XX series AT command manual covers TCP/UDP, HTTP(S), MQTT and, on GNSS variants, positioning (`AT+CGNSSPWR`).

## Documentation

Hardware design and AT command manuals for the A7670 series are on the [A7670X product page](https://www.simcom.com/product/A7670X.html). The downloads need a free SIMCom account.

## Schematic

[`schematics/modbee-hat-lte.pdf`](https://github.com/mod-bee/modbee-hats/blob/main/modbee-hat-lte/schematics/modbee-hat-lte.pdf)

## Licence

[CC BY-SA 4.0](https://github.com/mod-bee/modbee-hats/blob/main/LICENSE)