Issue #265: i2c scan & pull-ups

[Bus-Pirate]

i2c scan & pull-ups:
I updated the firmware and now i2c scan no longer works. I have a device attached to my BP and set it in 12c mode. I set the woltage and pullups. Then

I2C> P
Pull-up resistors: Enabled (10K ohms @ 3.3V)

I2C> scan

Error: Pull-up not detected on IO pin
Hint: Use P to enable pull-up resistors, or use external pull-up

Aborting I2C scan

I had enabled pullups. The configuration is

I2C> i

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions:
(1) this device may not cause harmful interference, and 
(2) this device must accept any interference received, including interference that may cause undesired operation.

Bus Pirate 6
https://BusPirate.com/
Firmware main branch @ a3b3977 (Nov 10 2025 13:16:25)
RP2350B with 512KB RAM, 128Mbit FLASH
S/N: 442CD5B5206B7C03
Storage:   0.10GB (FAT16 File System)

Configuration file: Loaded
Active binmode: Follow along logic analyzer
Available modes: HiZ 1WIRE UART HDUART I2C SPI 2WIRE 3WIRE DIO LED INFRARED JTAG
Active mode: I2C
 I2C speed: 100 kHz
 Clock stretching: OFF 

Display format: Auto
Data format: 8 bits, MSB bitorder
Pull-up resistors: ON
Power supply: ON (3.3V/3.29V)
Current limit: OK (4.8mA/300.0mA)
Frequency generators: OFF

Since this was related to a firmware change, I did some investigation,
Version
Firmware main branch @ 7c08a5d (Feb 6 2025 14:48:19)
works. Version
Firmware main branch @ f0b199b (Mar 8 2025 11:44:56)
does not work.

Issue opened by: grymoire

[ian]

I’m not having this issue, but I am having another issue with scan limited to BP6. I’m debugging this issue now.

[ian]

On my hardware, I’m not getting any I2C output on 6, from latest firmware back to the March 8 version you post. None of them work at all.

The hardware otherwise seems fine.

I2C> P
Pull-up resistors: Enabled (10K ohms @ 3.3V)

I2C> scan
I2C address search:
0x2D (0x5A W) (0x5B R)
0x36 (0x6C W) (0x6D R)
0x53 (0xA6 W) (0xA7 R)
0x57 (0xAE W) (0xAF R)

Found 8 addresses, 4 W/R pairs.

I2C>

Update: ok, this is weird. It seems to be an issue with one particular 6, even though it passes self test. The other does I2C fine. I will need to dig deeper.

However I do not have the same issue with scan that you observed using the latest firmware.

Do all the voltages look right? IO0 and IO1 actually at 3.3volts?

[ian]

So… E9 strikes again The Bus Pirate 6 I was testing with did not have the E9 bug fix. In fact, I only have half-fixed hand reworked boards for testing the initial fix.

[Bus-Pirate]

Investigated this, but was not able to reproduce. Is it still an issue? Is one of the devices holding the I2C pins low?

Here is a scan with a device attached.

Bot-copy from GitHub comment by: DangerousPrototypes