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Forum Index : Microcontroller and PC projects : Pico with ST7920 LCD in SPI mode
| Author | Message | ||||
| 58kk90 Regular Member  Joined: 14/06/2023 Location: United KingdomPosts: 49 |
I've been trying to get one of the ST7920 Chinese Ebay 128 x 64 LCD's running with a Pico without any success. I am running version 5.08.00 and have the display wired in SPI mode following the wiring in an earlier thread on here. Like this LCD Reset (pin 17) goes to GP3 LCD RS (pin 4) goes to GP5 LCD RW (data in pin 5) goes to GP7 LCD E (clk pin 6) goes to GP6 Then I have Gnd connected to pins 1,15 and 20 and VCC connected to pins 2 and 19. First problem I have is when I do OPTION LCDPANEL ST7920, LANDSCAPE,GP5,GP3 I get an error 'Error : duplicated pin' I have checked and neither GP5 or GP3 are used for anything else, this happens from the get go after an 'option reset' and with no program uploaded to the pico. Anyone else tried these type of display's and had them working at all? Tony. |
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 6781 |
I think you might need to set it up like this: SETPIN GP5, DOUT 'the SETPIN commands may not be needed SETPIN GP3, DOUT OPTION SYSTEM SPI GP6, GP7, GP8 'this is the hardware SPI port OPTION LCDPANEL ST7920, LANDSCAPE, GP5, GP3 'any pins can be used for these You can't use that SPI bus for anything else as this display has a fixed CS that's always enabled. I must admit that I've not used one of these. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| 58kk90 Regular Member Joined: 14/06/2023 Location: United KingdomPosts: 49 |
Hi Mixtel90 Thank you for the help, I have tried what you suggest, following an 'option reset' I enter SETPIN GP5, DOUT SETPIN GP3, DOUT OPTION SYSTEM SPI GP6, GP7, GP8 and after entering the last line above I get Error : not valid SPI pins Tony |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9110 |
I think there may be a bug in the firmware for the ST7920. I can't work on it until later this month. In the meantime I wouldn't waste too much time on it until I have a chance to test/fix |
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| 58kk90 Regular Member Joined: 14/06/2023 Location: United KingdomPosts: 49 |
Thanks Peter, I had wondered if that was the case or if it was something I was doing. I'll keep an eye on the forum until I see something from you that confirms it one way or another. Tony |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9110 |
Please try the version just posted on the release candidate thread. You should now be able to configure the display but I can't test any further than that as no access to a display until the end of the month Edited 2024-07-16 21:46 by matherp |
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| 58kk90 Regular Member Joined: 14/06/2023 Location: United KingdomPosts: 49 |
Thanks Peter, I tried the version which seems to be the latest from the release candidate thread 5.09.00RC5 and I appear to get the same as with 5.08 OPTION SYSTEM SPI GP6,GP7,GP4 OPTION LCDPANEL ST7920, LANDSCAPE,GP5,GP3 The last line gives Error : duplicated pin I'll have a search to see if I can find a later version in the thread, but scanning quickly on my phone, that was the only one I could see. Tony |
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| 58kk90 Regular Member Joined: 14/06/2023 Location: United KingdomPosts: 49 |
Cancel the last, I have found the one you meant when you said 'just posted'. I'll give this version a try later this afternoon. Tony. |
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| 58kk90 Regular Member Joined: 14/06/2023 Location: United KingdomPosts: 49 |
Peter, I tried the 2024-07-16_212924 version, I no longer get the Error : duplictaed pin message, but the display shows garbage unfortunately. I can see the data, clock and RS pins toggling nicely on the scope though now which RS was not doing on the previous version. Tony. |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9110 |
This version is tested and working. I think the garbage was because I was clocking the SPI bus too fast. PicoMite.zip Connections as tested GND - 1,15,20 5V - 2,19 GP0 - 4 (RS) GP1 - 17 (RST) GP6 - 6 (E) GP7 - 5 (R/W)   |
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| 58kk90 Regular Member Joined: 14/06/2023 Location: United KingdomPosts: 49 |
Great thanks Peter, i'll try it this morning and report back .... Tony. |
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| 58kk90 Regular Member Joined: 14/06/2023 Location: United KingdomPosts: 49 |
I can confirm that it works perfectly using the Chinese Ebay ST7920 LCD's Tried both the white backlit version and the yellow backlit version, the yellow was the 3.3v version and the white was the 5v version, both work perfectly with the Pico. Thanks Peter. Tony |
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