Today Alexis delivered us the whole set of the train light circuit. Initially we tried to add another light card to our current testing configuration. We managed to get 2 light cards configured , so up to this point the central station has been able to control 2 light cards, the train and an ethernet connection in total.
Currently we are working on stabilizing the NMRAnet CAN bus protocol. We encountered problems of what we think mainly concern, a difference between the CAN bus bandwidth and the processing bandwidth of the central station. For example, as we observed, during programming the events of a node, within an environment of multiple CAN packets exhange, the central station missed acknowledgement frames sent by the node after the configuration file. This prevented the central station from successfully programming a node. After inserting a delay between sending the data of the configuration file and the ACK we observed that the node got successfully programmed. This led us to assume a mismatch in processing and CAN bus bandwidth.
In order to face these kind of problems which have appeared, we will adjust the CAN bus bandwidth, use one buffer for event processing and another one for network-management purposes, and additionally install event filters on the fly accordingly for each node.
Today we were able to control our leds using the TLC5945 Led Driver, although we have not yet exploited it’s capabilities at full extent. As Alexis and Samuel proposed during our meeting, we should use dot correction in order to balance the mismatch of luminosity between green, red and orange. In addition, it would be useful to control intensity through TLC5945 grayscale mode especially once we assemble the whole system containing 60 leds.
Our next PSSC concerns DCC control of the train , although there are many more things we are concerned about. At this point we are mostly concerned about switching from our laboratory based STM32F103 cards, to the STM32F107 based central station card. For the moment we haven’t yet achieved to configure the STM32F107 CAN bus drivers correctly. Once this is done we will do more tests and continue working on the stability of the NMRAnet CAN bus module.
One problem of the NMRAnet CAN bus net module is the fact that in presence of multiple producer consumer events, the nodes fail to reply in time, to the STATUS REQUEST message addressed to them by the central station at some point. We have thought that a possible fact that causes this situation is that for the moment nodes are using only one of the STM32F103′s available CAN bus reception FIFO’s. In this case, processing the status request incoming packets is being delayed by event packets already present in the FIFO . Therefore we think that filtering out NMRAnet producer/ consumer event packets from one of the FIFO’s and letting them pass thorugh the other one seems like an improvement.