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Project by Tim Blythman ESP32-CAM LCD BackPack After we reviewed the Altronics Z6387 ESP32 WiFi camera module, we thought it would be great with an LCD BackPack. The ESP32-CAM LCD BackPack PCB connects the ESP32 WiFi camera module to a 3.5in LCD touch panel and makes it easy to reprogram the ESP32 module. W e were impressed by the ESP32 WiFi camera module when we reviewed it in the February 2024 issue (siliconchip.au/Article/16129). It is a compact module with a WiFi-­ provisioned ESP32 microcontroller and an OV2640 camera chip. It is also called the ESP32-CAM (the name is printed on its board). The module is easy to use. While the easiest way to retrieve camera images was to use a separate microcontroller (such as a Pico W BackPack) with WiFi, the onboard ESP32 is a capable 32-bit microcontroller. So it makes sense to use it in a standalone fashion and remove the need for a second microcontroller. This straightforward LCD BackPack for the ESP32-CAM module lets you do that. The ESP32 microcontroller can display camera images on the 3.5in LCD touch panel, while other circuit features simplify programming and communication. We’ve also written some sample Arduino code that will provide a basic demo of the BackPack and form a starting point for writing your own ESP32CAM LCD BackPack code. To demonstrate the standalone nature of the BackPack, the demo code does not use the WiFi features of the ESP32 processor (but you can if you want to). ESP32-CAM recap The ESP32-CAM contains an ESP32 sub-module, which in turn contains the ESP32 processor plus some passive components and a flash memory chip, the latter storing the program that runs on the processor. There is also a 72 Silicon Chip PCB antenna for WiFi and Bluetooth. The ESP32-CAM module adds a camera chip that uses 1.2V and 2.8V supply rails, provided by a pair of onboard regulators. A serial PSRAM (pseudo-static random access memory) chip provides working memory for image processing. There is a microSD card slot, a pair of eight-way headers for external connections, one LED to perform the role of a camera flash, plus the necessary smattering of passive components. We included a circuit for the module in the review article. The ESP32 sub-module has a socket for an external WiFi antenna, which can be used (instead of the PCB antenna) by changing the position of a single jumper resistor. ESP32-CAM LCD BackPack Kit SC6886 ($42.50 + postage): comes with the PCB and all nonoptional onboard components except the ESP32-CAM module. It does include the touchscreen. These lines are not connected to anything unless a microSD card is fitted in the socket, so the solution is simply not to insert one. While disabling the microSD card slot is a hindrance, the ample flash memory of the ESP32-CAM module still allows data to be saved in non-­ volatile storage. There are Arduino libraries, such as LittleFS, that can treat the flash memory as a file system to read and write files. Fig.1 shows the resulting circuit of the ESP32-CAM LCD BackPack. As you can see, it mainly provides connections between the headers for the ESP32-CAM and the LCD touch panel via CON3. The six signals we freed up are the minimum necessary to update the LCD screen and sense touches on the panel. Three lines are used for SPI communication: SCK (IO14), MOSI (IO2) and MISO (IO4). The LCD and touch panel controllers each have a CS (chip select) line, for which we use IO12 and IO15, respectively. The LCD controller also has a D/C (data/command) line, which we connect to IO13 on the ESP32 microcontroller. The LCD controller’s RESET line is tied to the ESP32’s E32_RST line, so the LCD is reset whenever the processor is reset. In any case, a software reset command can be sent to the LCD controller over the SPI bus. The LCD panel’s LED control line is tied high, meaning there is no control of the LED backlight; it is fully illuminated as long as the BackPack is powered. The biggest compromise we have made is that one of the lines to the Australia's electronics magazine siliconchip.com.au ESP32-CAM LCD BackPack We noted in our review that practically all the ESP32’s I/O pins are used up by features on the module. The camera chip alone requires 15 lines. To free up enough pins to control an LCD touch panel, we need to lose some functionality on the ESP32-CAM. We have chosen to disable the microSD card slot, as there is no other way to free up six easily-accessible pins. Fortunately, its control lines are broken out to the module’s headers, so we do not need to modify the module to access them. Fig.1: the ESP32CAM LCD BackPack is a little more than a breakout board that allows the ESP32-CAM module to be connected to a 3.5in LCD touch panel. A header for a CP2102 USB-serial module and a pair of tactile pushbuttons allow communication and programming of the ESP32 processor on the module. LCD touch panel (IO4) is also used to control the flash LED. However, it was already shared with the microSD card socket, so that brings no new challenges. We are using this line for MISO (master in/slave out), which is only used by the touch panel interface chip. Since there is a pulldown resistor on this pin, and it is only driven high when the touch panel sends binary ‘1’ data bits, the flash remains off except for brief moments when the touch panel controller is communicating. It’s low again so quickly that the resulting LED illumination is barely visible. We have added extra rows of pads on the PCB to allow the available pins to be broken out. There likely isn’t much that can be done with these, short of sourcing 3.3V or 5V power for external circuitry. Still, there is plenty of free space on the board, and no extra cost to add those pads. We have also added a CP2102 siliconchip.com.au USB-serial module, attached to CON1. It can be used to supply 5V power to the ESP32-CAM’s onboard 3.3V regulator from a USB power source. We could have taken 3.3V from the CP2102 module. However, its regulator is integrated into the CP2102 chip and would probably not be able to supply the current needed by the ESP32 processor and camera chip. Naturally, the CP2102 module also connects to the ESP32-CAM’s serial communication lines, providing a USB serial terminal to interact with the BackPack. Since there is spare space, we’ve also added a mini-USB socket footprint, CON2, which can be used to provide power to the BackPack if the CP2102 module is not fitted. Finally, two tactile pushbuttons, S1 and S2, are connected to the RESET and IO0 pins, respectively, pulling them to ground when pressed. These can be used to reset the processor or to Australia's electronics magazine put it into bootloader mode for uploading new firmware. So, even if you don’t need to connect an LCD panel to the ESP32-CAM, the BackPack can make programming and communicating with the module easier. It is much tidier than using a breadboard, which is what we used when prototyping the software for this design. If you wish to experiment, you could carefully follow the Fig.1 circuit diagram and wire it up on a breadboard. Still, the ESP32-CAM LCD BackPack is easy to build and inexpensive, so we recommend doing that instead. Construction The ESP32-CAM BackPack is built on a double-sided PCB coded 07102241 that measures 99 × 55mm. During construction, refer to its overlay diagrams, Figs.2 & 3 that show which parts go where. The only somewhat tricky part of April 2024  73 the assembly process is ensuring that all the components are fitted to the correct sides of the PCB, but the overlay diagrams and photos will help with that. They are all through-hole parts except for the optional mini-USB socket, CON2. CON2 should only be fitted if you aren’t using a CP2102 module. Be aware that you will need another way to program the ESP32-CAM module in that case. If you are fitting CON2, do so first. Apply flux to the pads and solder the larger mechanical leads to the PCB after checking that the locating pins have aligned the socket correctly. Then, clean your iron and carefully solder the smaller pads. Clean off any flux residue once you have finished soldering CON2 using an appropriate solvent (most pure alcohols will work). Allow the PCB to fully dry before continuing. Two eight-way female header strips are used to mount the ESP32-CAM module. Temporarily fit them to the ESP32-CAM and slot those into the pads on the PCB, making sure it is on the side marked for the module. Solder the headers in place, ensuring everything is neat and square, then detach the ESP32-CAM module so it doesn’t get damaged during subsequent steps. Slot the two switches into place on the other side of the PCB and solder them to it, then fit the tapped spacers to the outermost set of holes on the main PCB, on the same side as the switches. They should align with the holes for the 3.5in LCD panel. The innermost holes will align with a 2.8in LCD panel, although our software will not work with the ILI9341 controller on those displays. Numerous libraries are designed for these controllers, so if you want to utilise a 2.8in panel, you could develop your own software to work with it. Most constructors should stick with the higher-resolution 3.5in panel as it doesn’t cost much more. Plug the 14-way header socket into the header on the 3.5in LCD panel and align the LCD panel to the main PCB with the tapped spacers. This will allow you to solder the header socket squarely to the PCB. Note that you cannot have the four-way header (for the SD card socket on the LCD panel) fitted to the LCD panel, as it would foul the tactile switches. Also, remember that the CP2102 module needs to fit under the LCD panel. This module is usually supplied with right-angled headers, but you must use straight headers to mount it flat against the PCB. Sandwich the straight header between the PCB and the CP2102 module and ensure the CP2102 module is pushed down against the header. Tack one lead to the PCB and module, then confirm that everything is square and fits under the LCD panel before soldering the remaining pins. You can then trim the excess pin header length to keep the headers clear of the LCD panel. Another option is to use a matching set of male and female headers to allow the CP2102 module to be detached, although you may need to be creative to ensure that this fits under the LCD panel. If you haven’t already done so, fit the camera to the FFC (flexible flat cable) socket on the ESP32-CAM module. A pivoting black bar rotates upwards, allowing the cable to be slotted in. The black bar is pushed down to secure the camera. Then, use the attached tape to affix the camera chip to the microSD card holder on the module and plug the ESP32-CAM module into the headers. Fit the LCD panel and secure it with the screws. If you apply power now to the CP2102 module, you should see the LCD backlight illuminate, but not much else will happen until the ESP32-CAM is programmed to work with the LCD panel. Programming it Figs.2 & 3: the PCB is not difficult to assemble, although there are components on both sides. The eight-way male and female headers are fitted to the side marked ESP32 CAMERA MODULE. The remaining parts go on the other side, which faces the back of the LCD, allowing the camera to face outwards. We are using the Arduino IDE to program the ESP32 chip on the ESP32-CAM. To add support for ESP32 boards, go to the Board Manager section under the File → Preferences menu item and add “https:// dl.espressif.com/dl/package_esp32_ index.json” to the list of Board Manager URLs. Next, open the Board Manager itself and add the ESP32 board profile (search for “esp32”). You should add Australia's electronics magazine siliconchip.com.au 74 Silicon Chip Screen 1: the demo sketch updates the LCD panel as quickly as possible, showing the image at native resolution. At 96×96 pixels, it refreshes at 25fps, making it appear smooth. The camera orientation means horizontal and vertical flip must be on so the displayed image is the right way up. the version provided by Espressif Systems; there is also a version provided by Arduino, but it does not support the ESP32-CAM. We used version 2.0.14, but later versions should work equally well. Choose the “AI Thinker ESP32-CAM” board from the dropdown menu and set the serial monitor baud rate to 115,200. That is the default rate used by the ESP32, so it is handy for viewing boot and diagnostic data. Open the serial monitor to the serial port of the CP2102 module. Now open the “ESP32CAM_BACKPACK_DEMO” sketch and put the ESP32-CAM LCD BackPack into programming mode by pressing and holding S1 (RESET). While holding S1, press and hold S2 (IO0), then release S1, followed by S2. S2 must be held down when S1 is released to set the correct boot state. Pressing S1 first ensures that IO0 is not being driven by the ESP32 microcontroller when S2 is pressed. If IO0 is pulled low by S2 while being driven high, that could damage the chip (although it’s unlikely). You should see a ‘waiting for download’ message in the serial terminal, meaning that the ESP32 is in programming mode. If you see something different, try again. Upload the sketch, and the LCD should initialise and display an image. If that doesn’t happen within a second or two, briefly press the S1 (RESET) button to reset the microcontroller. If you still don’t see anything on the LCD, check the serial monitor for any error messages. That will include information about whether the camera was correctly detected and which model was found. There will be a constant stream of data as the sketch describes the images it is processing, so you may have to turn off auto-scrolling in the serial monitor. If the camera is not detected, power off the ESP32-CAM LCD BackPack and check the connection to the FFC connector on the ESP32-CAM module. Screen 2: the TEST button at upper right turns on the camera chip’s colour bar test. If you are not making out a clear image, the colour bar test should help identify whether the ESP32 is receiving correct image data. The colour bars’ appearance will change at different resolutions. Screen 3: at higher image capture resolutions, the demo sketch crops out the centre 240×240 pixels, which is like performing a digital zoom on the central part of the image. Here, we have tweaked the brightness and contrast settings to improve the image quality. Screen 4: the EFFECT setting activates image processing on the camera, providing special effects without extra load on the ESP32 processor. The EFFECT 2 setting is monochrome (compare this to Screen 3). The default effects set also offers reverse video and several colour tints. Demo sketch functions Screens 1 to 4 show some views of the LCD panel as it runs the demo sketch. The camera was pointed at a laptop screen showing the Silicon Chip website. The camera image is refreshed as quickly as possible and displayed inside the white rectangle. siliconchip.com.au Australia's electronics magazine April 2024  75 Parts List – ESP32-CAM BackPack 1 double-sided PCB coded 07102241, 99 × 55mm 1 UB3 Jiffy box (optional) 1 laser-cut Jiffy box replacement lid (optional) [SC5083 or SC5856] 1 ESP32-CAM module (MOD1) [Altronics Z6387] 1 3.5in LCD touchscreen (MOD2) [Silicon Chip SC5062] 1 CP2102 USB-serial module (MOD3) [SC3543] 1 6-way 2.54mm-pitch pin header (CON1; for CP2102 module) 1 SMD mini-USB socket (CON2; optional, instead of CON1) 1 14-way 2.54mm-pitch header socket (CON3; for LCD touchscreen) 2 8-way 2.54mm-pitch header sockets (CON4 & CON5) 2 8-way 2.54mm-pitch headers (CON6 & CON7; optional) 2 right-angled tactile switches (S1, S2) 4 12mm-long M3 tapped spacers 8 M3 × 5mm panhead machine screws 4 M3 × 8mm panhead machine screws (optional, to mount to acrylic lid panel) 4 1mm-thick, 6mm outer diameter M3 Nylon washers (optional, to mount to acrylic lid panel) The calculated frame rate is shown below the image. We found that the ESP32-CAM could achieve about 25fps (frames per second) when running at 96×96 pixels. Most of the processing time involves transferring data to the LCD controller. Several touch panel buttons are provided on the right. They are only scanned once per display update, so you may need to press longer when higher resolutions are set. The flash LED will flicker when the touch panel is scanned. The buttons provide access to a useful subset of the settings available on the camera chip. Later, in the Software section, we’ll note how you can find the full range of settings that can be changed from within an Arduino sketch. From the top, the TEST setting enables a colour bars test pattern, as seen in Screen 2. This can be used to test whether any problems are due to the camera chip itself, or if they are due to communications or processing faults elsewhere. The SIZE parameter cycles through several preset resolutions up to 640×480 pixels. Although the camera chip supports images up to 1600×1200 pixels, processing images that size would take too long and wouldn’t fit on the LCD screen without substantial cropping. Smaller images are displayed with a grey border, while images larger than the LCD resolution of 480×320 pixels are cropped, giving the effect of a digital zoom. 76 Silicon Chip The H-FLIP and V-FLIP settings mirror the image horizontally or vertically. We found that they both had to be turned on for the Altronics module to align the camera image with the image displayed on the LCD panel. The QUALITY setting changes the JPEG compression level used by the camera chip. Perhaps confusingly, lower numbers correspond to better image quality. This value can vary from four to 63, although we didn’t see much difference between the settings. The BRIGHTNESS and CONTRAST settings work as expected, although they can only vary from -2 to +2. Finally, the EFFECT setting provides some special effects performed on the camera chip, so they do not require any extra processing from the ESP32. The available effects include reverse video, black-and-white and several colour tints that can be applied. EFFECT 0 means that no special effect is applied. Software details Much of the demo sketch is involved in providing the user controls, allowing the settings to be tweaked. There is not much code needed if you simply wish to display an image from the camera on the LCD panel; the following is a guide to the minimum required to do so. The Arduino setup() function should call displaySetup() to initialise the LCD panel and camInit() to configure the camera chip. These functions can be found in the sketch folder, inside the files “LCD.h” and “camera_pins.h”, respectively. If you need to change the resolution, use the set_framesize() function. Like many other camera settings, this and similar functions are found in the “sensor.h” file, which is part of the ESP32 board profile. If you can’t find it on your computer, you can view it at https://github.com/espressif/ esp32-camera/blob/master/driver/ include/sensor.h To acquire an image, call the esp_ camera_fb_get() function. The frame buffer contains JPG data and can be converted to RGB bitmap data with the frame2bmp() function. Finally, the drawBitMap() function can be used to draw the bitmap to the LCD panel. This function definition can be found at the bottom of the main sketch. It takes care of cropping and Here is the BackPack board without the touchscreen panel, so you can see the positions of the USB-serial adaptor and right-angle tactile pushbuttons. The ESP32-CAM module mounts on the opposite side (it’s shown separately on the right). Australia's electronics magazine siliconchip.com.au ensuring that the RGB data triples are output in the correct order. You need to release the JPG buffer with esp_camera_fb_return(), and the bitmap buffer with free() once you have finished processing the data and before starting the next acquisition, or the program will quickly terminate due to memory exhaustion. The “ESP32CAM_BACKPACK_ DEMO_minimum” sketch from the software downloads is nearly the minimum needed, apart from some diagnostic error messages. It simply displays a camera image in the centre of the LCD. We have also written a sketch named “ESP32CAM_BACKPACK_FILE_ CAMERA”. This sketch programs the ESP32-CAM LCD BackPack to behave like a very basic digital camera, capturing and displaying images to and from the internal flash-based LittleFS file system. It has a small viewfinder preview that constantly updates and buttons to allow digital zooming up to four times. You can also scroll through the saved images and format the file system to delete all saved images. Enclosure option The stack of three PCBs, including ESP32-CAM module, BackPack PCB and LCD panel, stands roughly 40mm deep when assembled. It will thus fit neatly into a 44mm deep UB3 Jiffy box, such as Altronics’ H0203. The camera lens will sit a few millimetres inside the base of the box, so you will need to drill a hole to allow the camera lens to ‘peek out’. Alternatively, longer spacers, like the stackable headers used for Arduino boards, could be used to position the camera lens just outside the base of the box through a hole. You can use our SC5083 or SC5856 laser-cut acrylic lid panels to mount the assembly. These are available from the Silicon Chip Online Shop. You might also need longer self-­tapping screws that can thread through the extra depth of the acrylic. We have noted these optional parts in the Parts List. Note that the lens is not centred on the BackPack PCB due to the asymmetry of the ESP32-CAM module. The LCD panel and thus the acrylic panels are not symmetrical either. Conclusion A camera is a very useful sensor to be able to connect to a microcontroller, allowing images of the world to be captured and displayed. While the ESP32 is known for its WiFi capabilities, it is also a capable 32-bit processor wellsuited to image processing. The ESP32-CAM module is useful on its own, providing many of the features of a basic WiFi camera. The ESP32-CAM LCD BackPack adds to this by processing and displaying camera images on an LCD touch panel. We think it will be of interest to those looking to perform low-level image capture and processing. While adding the LCD panel to the ESP32CAM means that the onboard microSD card slot is not usable, alternatives such as the LittleFS flash file system SC exist. Ideal Bridge Rectifiers Choose from six Ideal Diode Bridge Rectifier kits to build: siliconchip. com.au/Shop/?article=16043 28mm spade (SC6850, $30) Compatible with KBPC3504 10A continuous (20A peak), 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: MSOP-12 (SMD) Mosfets: TK6R9P08QM,RQ (DPAK) 21mm square pin (SC6851, $30) Compatible with PB1004 10A continuous (20A peak), 72V Connectors: solder pins on a 14mm grid (can be bent to a 13mm grid) IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ 5mm pitch SIL (SC6852, $30) Compatible with KBL604 10A continuous (20A peak), 72V Connectors: solder pins at 5mm pitch IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ mini SOT-23 (SC6853, $25) Width of W02/W04 2A continuous, 40V Connectors: solder pins 5mm apart at either end IC1 package: MSOP-12 Mosfets: SI2318DS-GE3 (SOT-23) D2PAK standalone (SC6854, $35) 20A continuous, 72V Connectors: 5mm screw terminals at each end IC1 package: MSOP-12 Mosfets: IPB057N06NATMA1 (D2PAK) TO-220 standalone (SC6855, $45) 40A continuous, 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: DIP-8 Mosfets: TK5R3E08QM,S1X (TO-220) This is how the ESP32-Cam module mounts to the headers marked CON4 & CON5. The pin descriptions are marked on the other side of the PCB, as that is where we expect most readers will attach any accessories. siliconchip.com.au Australia's electronics magazine See our article in the December 2023 issue for more details: siliconchip.au/Article/16043 April 2024  77