Neoway M590

The solution to this problem is to ensure that ports on the MCU are configured low or to high impedance when power is removed.

Reset signal of the module. Pin 22 is emergency power off pin. Its function is similar to a hardware reset signal on a MCU. The minimum reset pulse width is 1ms.

VCCRTC is RTC power source. If VBATT is higher than 2.5V, VCCRTC will output a voltage of 2.5V continuously, irrespective of if module is in startup or shutdown or dormant.

Notice

The main power source should not exceed 4.8V. Over-voltage will damage the module. The most common failure in this event will be VBATT to Ground short internally in the module.

Failure at low temperature (-40C) is usually caused by power supply design, and choice of components not suited to this environment. When selecting capacitors for the power supply, make sure they specified to operate without significant reduction in capacity in the intended design over the operating temperature range. Failure of these capacitors to maintain their capacity at temperature extremes may cause the supply voltage to drop below 3.3V and will result in the modem shutting down. Exercise caution in the power supply design.

When supplying power to the module, DO NOT USE SERRIES diodes to directly step-down the voltage. Voltage drop across diodes varies greatly depending on current, and may result in an unstable supply and may cause operation issues with the module.

When doing static testing or surge testing, please ensure the stability of the power source. Power, ground, inputs and outputs should be designed to consider EMC and interference to prevent glitches and spikes. Ceramic capacitors are recommended for filtering.

Avoid long tracks on the On/off control (Pin 19) and use filtering techniques described to reduce interference and risk of accidental power on or off.

6.1.2 Power on/off Sequencing

Diagram 2 Power on / off process

Supply power to MCU first, then supply power to the main power source of the module, to prevent incorrect operation in the event of unstable levels on the IO. Ensure the MCU is operating stably, prior to supplying supply power to the module ON/OFF.

6.1.3 Pin Description

Pin19 ON/OFF is an input pin. The startup and shutdown of the module can be controlled externally by this pin – active low. and effective on low level. There is a weak internal pull-up for ON/OFF in the module.

Power on process:

1)Apply power to the module (Pin 2 and Pin 3)

2)Pull down the ON/OFF control (Pin 19) for more than 300ms (500mS minimum recommended)

3)The Modem will automatically generate “Modem Startup” on the serial port and the LED will flash for 1 second.

4)VCCIO will output 2.85V continuously

Note that the ON/OFF control pin (Pin 19) can be connected permanently to ground in

which case the module will power up automatically when power is applied

Power off process:

1)If the ON/OFF Pin is high (Pin 19) it should be pulled low and kept low for a minimum of 300ms. Alternatively the Module may be powered down by an AT command. Refer the AT command manual.

2)The Module will automatically begin the power down routine and log off the network. The power down routine takes approximately 5 seconds.

3)Turn the main power source off (Pin 2 and Pin 3)

Inverting the logic for start-up and shutdown can be achieved using a single transistor

as shown in diagram 3.

Diagram 3 Recommended circuit for high level startup for M590

Notice:

The ON/OFF pin is a control signal which will switch the modem between the on and off state. Do not send more than one “on” command or one “off” command when powering up or power down the module as each instruction will toggle the Modem between the on and off state. Further to this, sending two pulses may result in the module being off, and it may be possible that the I/O has information from the MCU which results in current flowing as indicated in Daiagram1. This may cause start up failure. Follow the correct power up and power down procedure.

If the module doesn’t work normally, the module can’t be shutdown normally.

6.1.4Module Abnormality Recovery

Because of the complex nature of the product and the network, as well as the harsh environment the unit may operate in for extended periods of time, it is possible that the module may “crash” or lose connection to the network. Therefore it may be necessary to restore the connection in the application design. We recommend two methods:

1)Through the module main power source. Turn off the main power source for long enough for the supply voltage to decay through 3.0V and then supply voltage again observing the correct start up procedure. For devices that are inaccessible or remotely positioned this is the most reliable solution.

2) Pull the EMERGOFF (emergency shutdown) pin (Pin 18) low for 100ms in order to hard shutdown the module. This is similar to a processor hard reset and is typically used in hand held devices. If the module cannot recover in this way it is necessary to use the poer off method described above..

Prior to power removal or reset, regardless whether the module responds, follow the suggested power down sequence and wait at least 5 seconds Prior to rebooting. This is important to prevent corruption and possible program damage in the event of the module performing write instructions to FLASH, when power is removed or the unit is hard reset.

Pull up EMERGOFF pin on the module to VCCRTC, this moment external can’t enter a higher level, or may cause an exception when power on. EMERGOFF module internal connection diagrams please refer to figure 1. When supplying power to reset, EMERGOFF will output a low level, whose pulse width is 22ms.

Emergency shutdown circuit design recommendations:

1)EMERGOFF should be OC output, as shown in Figure 4.

Diagram 4 EMERGOFF OC Control(C6 R11 should close to the module pin)

2)The effective emergency shutdown pulse width of EMERGOFF should be at least 1ms. Effective low level can't be more than 0.4V.

3)If there is no need, EMERGOFF can be suspended.

6.1.5 VCCIO Pin Description

Pin 6 VCCIO is the reference voltage the module supplies, with an amplitude of 2.85V, and a loading capacity of3mA. Its suggested use is for switching interface level only. When power off, VCCIO output shutdown.

Moreover, this pin can be used to indicate the running status of the module. When it’s running normaly or sleeping, this output is high, and when the power module is powered down the pin is low.

Notice:

If the module is powered on, this can be confirmed by the VCCIO pin and LED pin. When the VCCIO pin is high (2.85V ) and a high and low level pulse on the LED pin, this confirms that the module is powered on. The serial port should also function in this instance, if not check that:

The RX/TX are not reversed, that the level converting circuit is correct, and that soldering is correct. Check the waveforms are square, and that the filter capacitors on the serial port are not too large.

As the Module is the DCE devise and the terminal is a DTE device connect the devices as shown in Diagram 5

Diagram 5 DCE and DTE signal connection diagram

The CMOS interface signal level is 2.85V, and should nor exceed 3.3V. Data rates supported are 1200,2400,4800,9600,19200,38400,57600,115200bps. The default rate is 115200bps.

When designing the serial communication interface circuit, a series resistor should be used should the external MCU be operating on a higher voltage – a 200 Ohm resistor should be used if the external MCU is operating on 3.3V. The resistor should be placed near the signal source. Refer Diagram 6 below.

Diagram 6 3.3V MCU and module serial communication recommended circuit Should the external MCU be operating on a higher voltage a level switching circuit is

recommended. Refer Diagram 7.When the MCU voltage is 5.0V, module reception should be performed level switch (Note that this level converting circuit don't support module

software upgrade, please choose the options as needed). Reference circuit is as follows:

Diagram 7 5.0V MCU and module serial communication recommended circuit

A filter capacitor of 100pF should be placed near the module receive pin in Diagram 6 and 7. The capacitor should not exceed 470pF

Notice:

On power up of the module ensure no serial data generation is present, and delay any data for at least 2 seconds after successful power up to ensure no errors.

Serial ports are typically used via AT commands, data services, upgrading the module software etc. Be aware that the module does not at present provide at DCD/DSR functionality

Table 6 Digital IO (without SIM card) input / output characteristics

Digital IO input / output characteristics description

DTR is the low power control pin, and if not required can remain unconnected if there is no need, it can be suspended. For low-power usage, please see the AT commands.

RING signal indication

1)Call In response to a call RING will cycle 5 seconds of low pulses of 30ms duration. Upon connection of the call Ring will return its state to high level. When there is a call, it will output a low pulse which cycle is 5s and width is 30ms. When the call is connected, it will restore to be high level.

2)SMS In response to an SMS Ring will pulse low for 35ms.

Notice:

If not used the DTR pin and Ring pins may be short circuit.

Serial filter capacitors cannot be greater than 470pF, otherwise that will cause distortion of serial waveforms, resulting in the disconnection of the serial port In the event of the serial port not functioning correctly remove the filter capacitors to confirm operation. Recommended value for filter capacitors is 100-220pF.

The resistance of the connection between the CPU and the Modem, the lower the achievable baud rate, be aware of this when designing the PCB. Also take care of crosstalk between the TXD and RXD line by keeping then apart with a spacing of at least 3 times the track width. Avoid running the lines parallel to each other for long distances, and where possible run a ground plane close to these lines to avoid interference. Use through holes to link the ground planes on the various layers.

6.3 SIM card Interface

Table 7 SIM card interface

Diagram 8 SIM card interface design reference

The module supports 3V and 1.8V SIM card with adaptive functions.

Pin23 SIMVCC is the power supply of SIM card, 2.85V and load capacity of 30mA. This pin outputs power t only when operating the SIM card.

Pin24 SIMIO need an external resistor pull up to SIMVCC, size of the pull-up resistor can be selected based on the SIM card routing, but typically 10K.

Pin25 SIMCLK is the clock line of SIM card, typically 3.25MHz. This track should be kept thin, short and direct. It should be surrounded by ground plane, and routed well away from the antenna and RF section. Total distributed capacitance on this track cannot exceed

100pF.

The SIM card connector should be placed near the corresponding connections on the module. Avoid long PCB tracks and place filter capacitors in the 27-39F range on the tracks. Close proximity to the radio frequency radiation (particularly with internal or rubber rod antennas) may result in reading abnormalities and corruption. Alternatively close proximity of the SIM to the antenna may result in decreased sensitivity.