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Forum Index : Microcontroller and PC projects : Understanding USB with PicoMite with LCD panel
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| Xian Newbie  Joined: 19/03/2025 Location: GermanyPosts: 25 |
Hey There, as a newbie i still have some issues to understand the different version of PicoMite and how to mitigate. My plans are (1.) build a boot 2 Basic computer with HDMI. I have puchased the Olimex board for this and this is working pretty good. I can access the SD card. I have a tiny keyboard connected, the real time clock is working well, the HDMI interface is working well and from my perspective, i just need to find or design a housing and then i have what i'd planned to have. So (1.) working without any issues at the moment. Plan (2.) - i want to build a portable version of (1.). For this case i have the Waveshare 3.5 touch display and a Pico with RP2040 working. Panel is displaying, SD card is accessible. No rtc yet. My problem is that i'd like to attach a keyboard to that setup but do not find a solution for this. As soon as i install the the USB version of the firmware, i cannot access the board via serial port. the display is dark and not displaying anything at all. How can i do the necessary setup via serial console and then finally attach a USB keyboard? Any advises highly welcome. Thanks a lot and best regards, Christian |
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Geoffg Guru  Joined: 06/06/2011 Location: AustraliaPosts: 3269 |
It should work. Are you using the PicoMiteRP2040USB version? Note that this version does not automatically direct the console output to the LCD panel. For this you need to use OPTION LCDPANEL CONSOLE. See the user manual page 62. This should work using pin 11 (GP8) for the serial console Tx and pin 12 (GP9) for Rx. See the user manual page 33. Geoff Geoff Graham - http://geoffg.net |
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| IanT Senior Member  Joined: 29/11/2016 Location: United KingdomPosts: 105 |
There may be a conflict in this case as the Waveshare 3.5" uses GP8/9 for LCD data and select. See pinout defintion at: https://www.waveshare.com/Pico-ResTouch-LCD-3.5.htm I was looking at a similar use (Boot2Basic) for my Grandson and noticed the new (?) 7/10" DVI screens from Waveshare - https://www.waveshare.com/pico-dvi.htm?sku=25509 I'd prefer a larger screen (coupled to a small USB keyboard) for him. I wasn't sure if the HDMI/USB firmware pinouts could be changed to accomodate those used by these displays. They do bring out UART & I2C signals but they unfortunately do not have an SD Card slot onboard, so I will maybe look at other ideas. I have an RP2350B running on an external HDMI screen (with SD card) but have not changed it to use a USB keyboard as yet. The larger WS screens (with the Pico socket) would be a much neater solution to my current 'homebrew' setup and at £22/£28 would have been an affordable option... Regards, IanT |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10066 |
To use this display you need to allocate the serial console to different pins (e.g. GP0,GP1). First load clear_flash on the pico to get rid of any previous configuration. Load the PicoMiteUSB firmware with the Pico unplugged from the display and with a USB UART connected to GP8/GP9. Connect to the USB/UART using teraterm or whatever. Re-allocate the serial console OPTION SERIAL CONSOLE GP0, GP1 Then connect the USB/UART to those pins. Assuming that works you can now plug the Pico into the waveshare display and complete the configuration by hand. The waveshare board does not give you access to pins so you will need wire directly to the Pico to provide 5V power on pin 40 and connect the USB/UART and connect GND |
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| Xian Newbie Joined: 19/03/2025 Location: GermanyPosts: 25 |
Thanks for you input to all! @matherp, when you say "Then connect the USB/UART to those pins. (after option serial console gp0,gp1)". You mean that i should use a ftdi or different module with an external UART, correct? Thanks again and best regards, Christian |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10066 |
Yes: Any of the USB firmware variants needs an external USB UART to convert the TTL level serial output to connect to a computer. The onboard USB is now dedicated to be a host port. |
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| Xian Newbie Joined: 19/03/2025 Location: GermanyPosts: 25 |
Thanks @matherp - wasn't aware of that. Now i understand my problems and have the solution. Thanks and best regards Christian |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7499 |
When you use the USB firmware the USB socket is put into Host mode. When that happens you can no longer use it to connect a console (e.g. Tera Term on a PC). By default GP8 and GP9 are then used for the console with a USB-TTL converter. However, that Waveshare module won't let you do that and the defaults have to be overridden. So yes, you'll need a USB-TTL converter on GP0 and GP1 as matherp has suggested. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Xian Newbie Joined: 19/03/2025 Location: GermanyPosts: 25 |
Good Evening! so, some steps further but just crashed onto the next block. The details: - soldered an FTDI serial2USB module to the Pico (gp8/9) - installed the USB software on the Pico (outside the Waveshare display) - booted the system and entered the command OPTION SERIAL CONSOLE GP0, GP1 - powered off, resoldered the RX/TX to GP1/GP0 - powered on (outside Display module) to check it working - works! - powered off, pressed the pico into the waveshare module, powered on, connected - until here all fine, but now when i enter the option command OPTION RESET PICO-RESTOUCH-LCD-3.5 i get the reply "Error : Invalid board for this firmware." Using the NON-USB Software i could select that option and the display was working with all options. What do i do wrong? Does any of you have any idea? Thanks and best regards Christian P.S. forget to mention that i am using the latest beta/RC V6.00.02RC8 P.P.S. and no i have seen that there is already a version RC14 which i will try first Edited 2025-04-15 03:36 by Xian |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10066 |
OPTION SYSTEM SPI GP10,GP11,GP12 OPTION SDCARD GP22 OPTION LCDPANEL ILI9488W,L,GP8,GP15,GP9,GP13 OPTION TOUCH GP16,GP17 should get you started |
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| Xian Newbie Joined: 19/03/2025 Location: GermanyPosts: 25 |
Thanks @matherp that worked fine, thanks for clarification and support. just one question left at the moment. i added the option OPTION LCDPANEL CONSOLE to get output to the display. That worked fine, however, the option got "extended" to OPTION LCDPANEL CONSOLE ,,,,,NOSCROLL and the system does not scroll at the end of the screen (as in the option). Can that be avoided? Or is it the display itself which disabled scrolling? Thanks and best regards Christian Edited 2025-04-15 05:18 by Xian |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10066 |
The Waveshare board does not support reading the framestore so can't support scrolling. The firmware compensates by clearing the screen and starting at the top when full |
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| Xian Newbie Joined: 19/03/2025 Location: GermanyPosts: 25 |
thanks a lot for clarification! Thanks and best regards Christian |
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