BV503 i1 MX3 a (PCB designation BV503_i2_b)

1) Wi-Fi Module

2) Power supply module, the processor is under this

3) Partial Sideways connector for sws modules see www.pichips.co.uk

4) SPI connector

5) I2C connector

6) U2 Connector (UART 2 on ByPic, also Interface 2 on Wi-Fi Module ** see 8)

7) U1 Connector (UART 1 on ByPic, also Interface 1 on Wi-Fi Module)

8) Serial disconnect jumpers, disconnects U2 from Wi-Fi

9) Misclanious connector

10) Relay bank 1 connector for 8 relays

11) Relay bank 2 connector for 8 relays

12) LCD interface connector for driving a

12a) Contrast trimmer for LCD display

13) User jumpers

14) Power input can accept AC or DC any polarity up to 30V

15) R- ByPic processor reset, W - general purpose used defined button

16) LED indicators - all user defined except pwr indicator

17) SD Card holder on underside of board.

Power Input [14]

The power supply can be AC or DC and up to 30 Volts. There is a bridge rectifier and smoothing capacitor before it goes into the voltage regulator [2]. This means that the board can be supplied from just about anything that can supply between 7 and 30 volts, this includes a mains transformer and a car battery.

The 5V output is capable of about 2 to 3A and so can supply external devices quite easily. The DC output from the rectifier is taken to some GPIO ports, the voltage will depend on the input, but it will be DC. This could be used for supplying a motor on the SWS interface for example.

There is a 3.3V supply, this is derived from the Wi-Fi module and powers the ByPic, there is a small capacity still left but this will be in the order of a few mA, probably 10 to 50. This can be used to power individual IC’s or modules that require little power.

The power module itself is based on the LM2596 and has an adjustable output. This is set for 5V and MUST NOT be adjusted to any other voltage. The module sits over the CPU and other components.

Serial Paths

The device is controlled by ByPic from UART2, this is the main programming interface for ByPic. There are several methods to access both UART’s and from different devices.

This section explains how to use the serial access using the ports as shown in the diagram.

Green Path

This may not be required, however it may be difficult to establish a wi-fi connection and so this interface [6] has been provided. The serial jumpers [8] must be removed to prevent the wi-fi module from interfering with communication. Simply connect a USB to Serial device and select the correct COM port. The baud rate is 115200.

There is a slight advantage to this interface in that it is quicker at downloading than using the socket method. It would also be used if there is any difficulty with establishing a wi-fi connection as you can se what is going on and also run functions for diagnosis.

Typical USB to serial converter.

Blue Path

This path is the preferred method once a wi-fi connection has been established, although if a lot of development work is needed then using the green path will afford better speeds when downloading.

To use this a wi_fi connection is needed and the serial jumpers [8] need to be in place. BvSerial can be used as a socket can be specified. Using the default(in default.cfg) ports and assuming that the device address is the flowing will establish a connection as shown.


Of course your network may be different. The main advantage of this is that no physical connection to the device is required, debugging and programming can be done at a remote location.

Shows how to connect to a socket so that programming can be done remotely. The Blue and Green paths therefore control and program the ByPic device.

Red Path

ByPic can control UART 1 under program direction. The path shown here is a direct connection to UART 1 so any information that comes from outside can be captured, processed and acted upon. The information comes in via a socket. In the case of a web browser this is just another socket and the information can be processed in a certain way.

As an example a browser will send a request, this will get to UART 1 via this path. A ByPic program is running that can detect when bytes are available on UART 1. The Bypic program can then decide what to do with the request. Any information sent out on UART 1, provided it is in the correct format will also be received by the browser.

That is an example of a web server. Of course it does not have to be a web browser, it is just that a web browser is on every host device.

Light Blue Path

Accessed via [7]. This should not be needed and is provided for deep troubleshooting purposes as it will give direct access to the wi-fi AT command set. There are some tools provided by the manufacturer that can be used with this path and are included on the zip file, but can also be downloaded form the manufacturers web site.

Wi-Fi Module

This is a HLK-RM04 that is described as a wi-fi UART. It is the link from the ByPic to the network and so potentially all the resources from the internet are available. The module can be used as a client to join an existing network or it can be used as an access point.

IMPORTANT The sockets used on the BV503 are shorter than the pins on the Wi-Fi module, if the module is removed take care that the unconnected pins are nearest the edge of the PCB


There is a built in real time clock. This does not have a battery back up and so requires re-setting at switch on. The time can be obtained from one of the many time services. The current ByPic code simple requests a web page from google that has the time and date as part of the head.

SPI Connector [4]

This is provided for SPI devices and is fully user programmable using ByPic functions.



CS (RG9)


(ch1 RG8)

(ch1 RG7)

MOSI is Master Out Slave in
MISO is Master In slave Out

I2C Connector [5]

For I2C slave devices, this is a master connector.


(ch1 RG3)


(ch1 RG2)

Pull up resistors are installed on the SDA and SCL lines.

SWS Connector [3]

This was intended as a SWS connector, however for this version it is a general purpose connector.







(SDA1, RG3)


Miscellaneous Connector [9]

This has the various power outputs and some I/O

+V, rectified DC output from the input

Regulated DC 5 Volts

Output from Wi-Fi module





Relay Bank 1 & 2 [11] & [10]

These are designed for opto isolated relays and can make a pin for pin connection to the relays that can be supplied. When not used for relays they can be used for any GPIO purpose. RD3

Bank 2











Bank 1












LCD Interface [12]

This is designed for a character type display of say 16x2 or 20x4 lines. This will be pin for pin compatible with most displays and also has a contrast pot at [21a]













V0 is connected to the wiper of the 1k trimmer.

The interface is software driven using ByPic functions. When not used for an LCD interface it can be used for any purpose.

User Jumpers [13]

These are two jumpers that when open will read high and when closed will read low. They can be used for any purpose.

J1 (RB15)

J2 (RB14)


Reset Buttons [15]

The right hand button marked R is connected to the ByPic reset. The left hand button is connected to RC15 and will read high when not pressed and low when pressed. This button can be used for any purpose.

LED Indicators [16]

The Pwr indicator is connected to the +3v3 supply and so will indicate when that is available. The other LED's are user selectable and can be activated under program control.






SD Card [17]

The holder for this is mounted on the underside of the PCB and takes a standard sized card. The operating system ByPic can read and write using either FAT16 or FAT32 with long file names.

HD cards are also acceptable up to 8MB (probably more but not tested)