From 1b692d09616da0d91e77cc342d1259f72044c9a2 Mon Sep 17 00:00:00 2001 From: Werner Almesberger Date: Fri, 29 Jun 2012 22:20:56 -0300 Subject: [PATCH] fw/ERRATA: add hardware errata and ideas for future improvements --- hw/ERRATA | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) create mode 100644 hw/ERRATA diff --git a/hw/ERRATA b/hw/ERRATA new file mode 100644 index 0000000..16b1a09 --- /dev/null +++ b/hw/ERRATA @@ -0,0 +1,28 @@ +- 4.5 V rail was intended to provide the ADXL32x with a supply voltage + that's at a safe distance from its 2.4 V minimum. However, the current + circuit wouldn't work with the acceleration sensor operating at 4.5 V. + It turns out the system operates well enough with the 4.5 V rail joined + to the 3 V rail. + +- the 6 V rail drops to 5 V after relatively little use. Need to improve + the power supply. + +- connections between boards are sensitive to mechanical forces and break + easily in the high-g environment we have here. Should consider moving + to an FPC at least for the LEDs. A stiff support beam (e.g., an + aluminium rail) helps to reduce mechanical stress. + +- the vertical resolution is a bit coarse. We could improve it and make + the whole system simpler by adding local demultiplexing with 74HC594 + or 75HC595. Such chips could drive the LEDs directly. + +- the battery pack needs room for a plug. (The original design assumed + the battery pack would be mounted on the stick, but this now seems + undesirable, due to the large weight. Current stick weight is about + 120 g and each AA battery would add about 25 g.) + +- the system really ought to have a button or even a joystick for user + input. + +- once a button is added, we could have local-only operation with images + coming from Flash.