While changing displays for our host controller from uLCD-43DT to gen4 50D CLB via gen4-PA, the serial port communication worked fine from the display to the host. However, the 50D was unable to receive any information from the host. Swapping around all combinations of two hosts, two 43DT's and two 50D's, as well as both ribbon cables and both gen4-PA's verified that the problem is consistent and repeatable. Further probing with the scope exposed the problem.
The Host TX to Display RX signal looked great, until the display was powered up from the host. After that, it would only swing voltages from 3.5v to about 2.0v. Obviously, an argument broke out on the bus.
Looking at the PA design and schematic, tt became apparent that it would work fine powering the host from the microUSB cable. But powering the PA and thus, the 50D from the host also powers up the CP2104 USB interface chip. Once that powered, the host is no longer able to override the now enabled TX output from the CP2104 chip. This put the utility of the gen4-PA as a breakout for breadboarding on hold. So what am I missing here?
How can I turn off the CP2104 chip while testing my host with the new gen4-DT display? Our host has the power supplies, battery, charger, regulators, etc. from which we power the display under host software control.
I have two PA's and may have to butcher one up for testing and another for display programming. An Eagle board file may help on where to add a movable power jumper - one position for programming (power from USB to display and CP2104) and another for host power (to test host/display only). Or if you have any alternative ideas, I am all ears.
I don't want to defeats the documentation warning about multiple connect/disconnect cycles with the FFC cable and connectors. Unfortunately, the 50D will need some programming changes due to the jump in pixles over the 43DT. Any ideas?
Thanks, Scott
The Host TX to Display RX signal looked great, until the display was powered up from the host. After that, it would only swing voltages from 3.5v to about 2.0v. Obviously, an argument broke out on the bus.
Looking at the PA design and schematic, tt became apparent that it would work fine powering the host from the microUSB cable. But powering the PA and thus, the 50D from the host also powers up the CP2104 USB interface chip. Once that powered, the host is no longer able to override the now enabled TX output from the CP2104 chip. This put the utility of the gen4-PA as a breakout for breadboarding on hold. So what am I missing here?
How can I turn off the CP2104 chip while testing my host with the new gen4-DT display? Our host has the power supplies, battery, charger, regulators, etc. from which we power the display under host software control.
I have two PA's and may have to butcher one up for testing and another for display programming. An Eagle board file may help on where to add a movable power jumper - one position for programming (power from USB to display and CP2104) and another for host power (to test host/display only). Or if you have any alternative ideas, I am all ears.
I don't want to defeats the documentation warning about multiple connect/disconnect cycles with the FFC cable and connectors. Unfortunately, the 50D will need some programming changes due to the jump in pixles over the 43DT. Any ideas?
Thanks, Scott
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