C API Documentation

The C API is very simple and consist of these two basic parts:

Lifecycle API
Modem commands

The Typical application workflow is to:

Create a DCE instance (using esp_modem_new())
Call specific functions to issue AT commands (Modem commands)
Switch to the data mode (using esp_modem_set_mode())
Perform desired network operations (using standard networking API, unrelated to ESP-MODEM)
Optionally switch back to command mode (again esp_modem_set_mode())
Destroy the DCE handle (sing esp_modem_destroy())

Note the configuration structures for DTE and DCE, needed for creating the DCE instance, is documented in Configuration structures

Lifecycle API

These functions are used to create, destroy and set modem working mode.

esp_modem_new()
esp_modem_destroy()
esp_modem_set_mode()

group ESP_MODEM_C_API

Set of basic C API for ESP-MODEM.

Typedefs

typedef enum esp_modem_dce_mode esp_modem_dce_mode_t: DCE mode: This enum is used to set desired operation mode of the DCE.

typedef enum esp_modem_dce_device esp_modem_dce_device_t: DCE devices: Enum list of supported devices.

typedef enum esp_modem_terminal_error esp_modem_terminal_error_t: Terminal errors.

typedef void (*esp_modem_terminal_error_cbt)(esp_modem_terminal_error_t): Terminal error callback.

Enums

enum esp_modem_dce_mode

DCE mode: This enum is used to set desired operation mode of the DCE.

Values:

enumerator ESP_MODEM_MODE_COMMAND: Default mode after modem startup, used for sending AT commands

enumerator ESP_MODEM_MODE_DATA: Used for switching to PPP mode for the modem to connect to a network

enumerator ESP_MODEM_MODE_CMUX: Multiplexed terminal mode

enumerator ESP_MODEM_MODE_CMUX_MANUAL: CMUX manual mode

enumerator ESP_MODEM_MODE_CMUX_MANUAL_EXIT: Exit CMUX manual mode

enumerator ESP_MODEM_MODE_CMUX_MANUAL_SWAP: Swap terminals in CMUX manual mode

enumerator ESP_MODEM_MODE_CMUX_MANUAL_DATA: Set DATA mode in CMUX manual mode

enumerator ESP_MODEM_MODE_CMUX_MANUAL_COMMAND: Set COMMAND mode in CMUX manual mode

enum esp_modem_dce_device

DCE devices: Enum list of supported devices.

Values:

enumerator ESP_MODEM_DCE_GENETIC: The most generic device

enumerator ESP_MODEM_DCE_SIM7600

enumerator ESP_MODEM_DCE_SIM7070

enumerator ESP_MODEM_DCE_SIM7000

enumerator ESP_MODEM_DCE_BG96

enumerator ESP_MODEM_DCE_SIM800

enumerator ESP_MODEM_DCE_CUSTOM

enum esp_modem_terminal_error

Terminal errors.

Values:

enumerator ESP_MODEM_TERMINAL_BUFFER_OVERFLOW

enumerator ESP_MODEM_TERMINAL_CHECKSUM_ERROR

enumerator ESP_MODEM_TERMINAL_UNEXPECTED_CONTROL_FLOW

enumerator ESP_MODEM_TERMINAL_DEVICE_GONE

enumerator ESP_MODEM_TERMINAL_UNKNOWN_ERROR

Functions

esp_modem_dce_t *esp_modem_new(const esp_modem_dte_config_t *dte_config, const esp_modem_dce_config_t *dce_config, esp_netif_t *netif)

Create a generic DCE handle for new modem API.

Parameters

dte_config – DTE configuration (UART config for now)
dce_config – DCE configuration
netif – Network interface handle for the data mode

Returns

DCE pointer on success, NULL on failure

esp_modem_dce_t *esp_modem_new_dev(esp_modem_dce_device_t module, const esp_modem_dte_config_t *dte_config, const esp_modem_dce_config_t *dce_config, esp_netif_t *netif)

Create a DCE handle using the supplied device.

Parameters

module – Specific device for creating this DCE
dte_config – DTE configuration (UART config for now)
dce_config – DCE configuration
netif – Network interface handle for the data mode

Returns

DCE pointer on success, NULL on failure

void esp_modem_destroy(esp_modem_dce_t *dce)

Destroys modem’s DCE handle.

Parameters: dce – DCE to destroy

esp_err_t esp_modem_set_error_cb(esp_modem_dce_t *dce, esp_modem_terminal_error_cbt err_cb)

Set DTE’s error callback.

Parameters

dce – Modem DCE handle
err_cb – [in] Error callback

Returns

ESP_OK on success, ESP_FAIL on failure

esp_err_t esp_modem_set_mode(esp_modem_dce_t *dce, esp_modem_dce_mode_t mode)

Set operation mode for this DCE.

Parameters

dce – Modem DCE handle
mode – Desired MODE

Returns

ESP_OK on success, ESP_FAIL on failure

esp_err_t esp_modem_command(esp_modem_dce_t *dce, const char *command, esp_err_t (*got_line_cb)(uint8_t *data, size_t len), uint32_t timeout_ms)

Convenient function to run arbitrary commands from C-API.

Parameters

dce – Modem DCE handle
command – Command to send
got_line_cb – Callback function which is called whenever we receive a line
timeout_ms – Command timeout

Returns

ESP_OK on success, ESP_FAIL on failure

esp_err_t esp_modem_set_apn(esp_modem_dce_t *dce, const char *apn)

Sets the APN and configures it into the modem’s PDP context.

Parameters

dce – Modem DCE handle
apn – Access Point Name

Returns

ESP_OK on success

Modem commands

These functions are the actual commands to communicate with the modem using AT command interface.

Note that the functions which implement AT commands returning textual values use plain char * pointer as the return value. The API expects the output data to point to user allocated space of at least ESP_MODEM_C_API_STR_MAX (64 by default) bytes, it also truncates the output data to this size.

Functions

command_result esp_modem_sync()

Sends the initial AT sequence to sync up with the device.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_operator_name(char *name, int *act)

Reads the operator name.

Parameters

name – [out] operator name
act – [out] access technology

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_store_profile()

Stores current user profile.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_pin(const char *pin)

Sets the supplied PIN code.

Parameters: pin – [in] Pin
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_at_raw(const char *cmd, char *out, const char *pass, const char *fail, int timeout)

Execute the supplied AT command in raw mode (doesn’t append ‘\r’ to command, returns everything)

Parameters

cmd – [in] String command that’s send to DTE
out – [out] Raw output from DTE
pass – [in] Pattern in response for the API to return OK
fail – [in] Pattern in response for the API to return FAIL
cmd – [in] String command that’s send to DTE
timeout – [in] AT command timeout in milliseconds

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_at(const char *cmd, char *out, int timeout)

Execute the supplied AT command.

Parameters

cmd – [in] AT command
out – [out] Command output string
timeout – [in] AT command timeout in milliseconds

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_read_pin(bool *pin_ok)

Checks if the SIM needs a PIN.

Parameters: pin_ok – [out] true if the SIM card doesn’t need a PIN to unlock
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_echo(const bool echo_on)

Sets echo mode.

Parameters: echo_on – [in] true if echo mode on (repeats the commands)
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_sms_txt_mode(const bool txt)

Sets the Txt or Pdu mode for SMS (only txt is supported)

Parameters: txt – [in] true if txt mode
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_sms_character_set()

Sets the default (GSM) character set.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_send_sms(const char *number, const char *message)

Sends SMS message in txt mode.

Parameters

number – [in] Phone number to send the message to
message – [in] Text message to be sent

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_resume_data_mode()

Resumes data mode (Switches back to the data mode, which was temporarily suspended)

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_pdp_context(esp_modem_PdpContext_t *p1)

Sets php context.

Parameters: p1 – [in] PdP context struct to setup modem cellular connection
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_command_mode()

Switches to the command mode.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_cmux()

Switches to the CMUX mode.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_imsi(char *imsi)

Reads the IMSI number.

Parameters: imsi – [out] Module’s IMSI number
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_imei(char *imei)

Reads the IMEI number.

Parameters: imei – [out] Module’s IMEI number
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_module_name(char *name)

Reads the module name.

Parameters: name – [out] module name
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_data_mode()

Sets the modem to data mode.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_signal_quality(int *rssi, int *ber)

Get Signal quality.

Parameters

rssi – [out] signal strength indication
ber – [out] channel bit error rate

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_set_flow_control(int dce_flow, int dte_flow)

Sets HW control flow.

Parameters

dce_flow – [in] 0=none, 2=RTS hw flow control of DCE
dte_flow – [in] 0=none, 2=CTS hw flow control of DTE

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_hang_up()

Hangs up current data call.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_battery_status(int *voltage, int *bcs, int *bcl)

Get voltage levels of modem power up circuitry.

Parameters

voltage – [out] Current status in mV
bcs – [out] charge status (-1-Not available, 0-Not charging, 1-Charging, 2-Charging done)
bcl – [out] 1-100% battery capacity, -1-Not available

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_power_down()

Power down the module.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_reset()

Reset the module.

Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_baud(int baud)

Configures the baudrate.

Parameters: baud – [in] Desired baud rate of the DTE
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_operator(int mode, int format, const char *oper)

Force an attempt to connect to a specific operator.

Parameters

mode – [in] mode of attempt mode=0 - automatic mode=1 - manual mode=2 - deregister mode=3 - set format for read operation mode=4 - manual with fallback to automatic
format – [in] what format the operator is given in format=0 - long format format=1 - short format format=2 - numeric
oper – [in] the operator to connect to

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_set_network_attachment_state(int state)

Attach or detach from the GPRS service.

Parameters: state – [in] 1-attach 0-detach
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_network_attachment_state(int *state)

Get network attachment state.

Parameters: state – [out] 1-attached 0-detached
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_radio_state(int state)

What mode the radio should be set to.

Parameters: state – [in] state 1-full 0-minimum …
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_radio_state(int *state)

Get current radio state.

Parameters: state – [out] 1-full 0-minimum …
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_network_mode(int mode)

Set network mode.

Parameters: mode – [in] preferred mode
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_preferred_mode(int mode)

Preferred network mode (CAT-M and/or NB-IoT)

Parameters: mode – [in] preferred selection
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_network_bands(const char *mode, const int *bands, int size)

Set network bands for CAT-M or NB-IoT.

Parameters

mode – [in] CAT-M or NB-IoT
bands – [in] bitmap in hex representing bands
size – [in] size of teh bands bitmap

Returns

OK, FAIL or TIMEOUT

command_result esp_modem_get_network_system_mode(int *mode)

Show network system mode.

Parameters: mode – [out] current network mode
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_set_gnss_power_mode(int mode)

GNSS power control.

Parameters: mode – [out] power mode (0 - off, 1 - on)
Returns: OK, FAIL or TIMEOUT

command_result esp_modem_get_gnss_power_mode(int *mode)

GNSS power control.

Parameters: mode – [out] power mode (0 - off, 1 - on)
Returns: OK, FAIL or TIMEOUT

Configuration structures

group ESP_MODEM_CONFIG

Configuration structures for DTE and DCE.

Defines

ESP_MODEM_DEFAULT_UART_CLK

ESP_MODEM_DTE_DEFAULT_CONFIG(): ESP Modem DTE Default Configuration.

ESP_MODEM_DCE_DEFAULT_CONFIG(APN): ESP Modem DCE Default Configuration.

Typedefs

typedef struct esp_modem_dte_config esp_modem_dte_config_t

typedef struct esp_modem_dce_config esp_modem_dce_config_t

Enums

enum esp_modem_flow_ctrl_t

Modem flow control type.

Values:

enumerator ESP_MODEM_FLOW_CONTROL_NONE

enumerator ESP_MODEM_FLOW_CONTROL_SW

enumerator ESP_MODEM_FLOW_CONTROL_HW

struct esp_modem_uart_term_config

#include <esp_modem_config.h>

UART configuration structure.

Public Members

uart_port_t port_num: UART port number

uart_word_length_t data_bits: Data bits of UART

uart_stop_bits_t stop_bits: Stop bits of UART

uart_parity_t parity: Parity type

esp_modem_flow_ctrl_t flow_control: Flow control type

uart_sclk_t source_clk: UART source clock selection

int baud_rate: Communication baud rate

int tx_io_num: TXD Pin Number

int rx_io_num: RXD Pin Number

int rts_io_num: RTS Pin Number

int cts_io_num: CTS Pin Number

int rx_buffer_size: UART RX Buffer Size

int tx_buffer_size: UART TX Buffer Size

int event_queue_size: UART Event Queue Size, set to 0 if no event queue needed

struct esp_modem_vfs_term_config

#include <esp_modem_config.h>

VFS configuration structure.

Public Members

int fd: Already created file descriptor

void (*deleter)(int, struct esp_modem_vfs_resource*): Custom close function for the fd

struct esp_modem_vfs_resource *resource: Resource attached to the VFS (need for clenaup)

struct esp_modem_dte_config

#include <esp_modem_config.h>

Complete DTE configuration structure.

Note that the generic part is common for DTE and its SW resources The following portions for config is dedicated to the chosen HW resource used as a communication terminal for this DTE

Public Members

size_t dte_buffer_size: DTE buffer size

uint32_t task_stack_size: Terminal task stack size

unsigned task_priority: Terminal task priority

struct esp_modem_uart_term_config uart_config: Configuration for UART Terminal

struct esp_modem_vfs_term_config vfs_config: Configuration for VFS Terminal

void *extension_config: Configuration for app specific Terminal

struct esp_modem_dce_config

#include <esp_modem_dce_config.h>

DCE configuration structure.

Public Members

const char *apn: APN: Logical name of the Access point