GP18and 19 resistors too low

[tony1tf]

This is a comment rather than a fault. I want to use GP18 and 19 as inputs in a logic analyser application. I love the Maker Pi Pico with its LEDs driven by FETS so they do not create a siginificant load on the inputs. However, the audio output socket is fed by a low resistance attenuator from GP18 and 19 with series resistors of 220 ohm and 100 ohm to ground. These are permanently wired in so they short out my high impedance inputs on these pins. I will have to remove the resistors R1 and R2 for my application. It would have been nice if they went through u-links to disconnect the load.

[tony1tf]

I also found that the V1.2 board has 10K pull-up resistors on GP20, 21 & 22 which I had to remove to get high impedance i/p. And I had to remove 0.1uF across the push buttons, else the signals get attenuated. In fact, I could do this by drilling through the VIAs connecting to R11, R64, and R65 near the ESP-01 socket.

[waiweng83]

Thanks for your feedback. I'm just curious, are all the other pins not used by the onboard peripherals already fully utilized?

[tony1tf]

Hi Wai I'm not using any peripherals at the moment, although I will have to give up some channels to use the WiFi if we decide to use it. Presently all logic analyser data from the input channels comes out through the USB. I liked the Cytron board for the blue LED displays which help me set up input attenuators for the non-standard logic levels we are using from a valve(tube) based computer (EDSAC) at The National Museum of Computing in the UK. The code is on github from Pico-Coder. Tony

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On Tue, 17 May 2022, 02:58 Wai Weng, ***@***.***> wrote: Thanks for your feedback. I'm just curious, are all the other pins not used by the onboard peripherals already fully utilized? — Reply to this email directly, view it on GitHub <#11 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABJKGTTNPZK7MZFD2CNC7BTVKL4KVANCNFSM5WBAQRTA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[waiweng83]

You may try to use those GPIO pins which is not shared with the onboard peripheral. eg:

GP0-9, GP10-15 (Shared with SD Card), GP16-17 (Shared with ESP01), GP26-27.