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Diffstat (limited to 'uart/counter/README')
| -rw-r--r-- | uart/counter/README | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/uart/counter/README b/uart/counter/README new file mode 100644 index 0000000..cc891bd --- /dev/null +++ b/uart/counter/README @@ -0,0 +1,38 @@ +------------------------------------------------------------------------------- +UART traffic, 5-9 data bits, counter values in data bits +------------------------------------------------------------------------------- + +This is a collection of example UART communication (TX only). The +data bits in the UART frame contain numeric values from a counter. +There are dumps for various numbers of data bits in the UART frames. + + +Logic analyzer setup +-------------------- + +The capture was taken with an ASIX Sigma2 logic analyzer at a sample +rate of 500kHz. The first three channels were enabled: + + Probe UART + ---------------- + 1 UART TX (counter values) + 2 UART RX (always idle) + 3 high for active UART frames + + +Data +---- + +The hardware sending the data is an Atmel ATmega328P. The bitrate is +always 19200, the frame format is 5n1, 6n1, 7n1, 8n1, 9n1 respectively. + +There is a pause between each UART frame (idle TX line for a few hundred +microseconds), such that decoders will immediately "lock in" to the +content, and manual inspection is simplified. + +Capture was arranged such that at least one full counter period is +covered and all possible data bit patterns are seen. + +The ATmega firmware asserts a GPIO line when a UART frame is being +sent. This is not essential for UART communication, but again is useful +for human inspection, and verification of protocol decoders. |