“Use a General Purpose Microcontroller to replace your Custom Chip
Are you being squeezed by Supply Chain Shortages?
Is your chip no longer being made?
Is there a firmware bug in your Chip?
Can’t get the chip you need for your project?
Then Hack the Chip and make your own!
We built our product using Maxim’s 1-Wire® to I2C DS28E17 bridge chip.
This allowed us to connect different I2C sensors, but discovered some issues.
- Only 3V3 Sensors could be used.
- If the Sensor required too much current it could cause a voltage drop or brown out, causing the DS28E17 to hang. Adding a large decoupling capacitor helped, but we were informed by Maxim to use the DS28E17 reset pin. Hello? I thought this was a 1-Wire® bus?
- No CRC Check on reading I2C data.
- Supply Chain Shortages. This chip is now really hard to get! Is the DS28E18 replacing the DS28E17?
- Supply and Demand led to steep price increases.
With these issues we then designed the next product using the DS28E18.
During the design phase we discovered a major issue.
- No Industry Standard I2C Clock Stretching! This was supported in the DS28E17 why did Maxim drop this critical compatibility feature? This issue was confirmed directly with Maxim.
So we can’t get the DS28E17.
The new DS28E18 does not work.
What can we do?
Hack the Chip!
To do this we need to first define all the requirements and find a suitable General Purpose Microcontroller. As it turns out the AVR ATTiny85 will meet our requirements, but it is going to be a challenge to get the high speed working. No worries we have a few programming tricks up our sleeves.”